Updated on 2022/11/02

写真a

 
YAMAGUCHI, Shigehiro
 
Organization
Institute of Transformative Bio-Molecules Professor
Graduate School
Graduate School of Science
Title
Professor

Degree 1

  1. 博士(工学) ( 1997.1   京都大学 ) 

Research Areas 3

  1. Others / Others  / Functional Material Chemistry

  2. Others / Others  / Synthetic Chemistry

  3. Others / Others  / Organic Chemistry

Current Research Project and SDGs 4

  1. Fluorescence imaging based on the development of fluorescent probes

  2. Synthesis of new pi-conjugated skeletons

  3. Synthesis of New Functional Organoboron Materials

  4. Synthesis of New Functional Organophosphorus Materials

Research History 8

  1. Nagoya University   Professor

    2012.4

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    Country:Japan

  2. Nagoya University   Research Center for Materials Science   Professor

    2012.4

  3. Nagoya University   Professor

    2005.3

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    Country:Japan

  4. 科学技術振興機構   SORST   研究員

    2004.12

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    Country:Japan

  5. Nagoya University   Assistant Professor

    2003.1

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    Country:Japan

  6. 科学技術振興機構   さきがけ「合成と制御」領域   研究員

    2001.12

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    Country:Japan

  7. Kyoto University   Assistant

    1993.11

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    Country:Japan

  8. Japan Society for Promotion of Science

    1993.4

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    Country:Japan

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Education 1

  1. Kyoto University

    1993.4 - 1993.10

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    Country: Japan

Professional Memberships 3

  1. 日本化学会

  2. 有機合成化学協会

  3. 基礎有機化学会

Awards 13

  1. Merck-Karl Pfister Visiting Professorship

    2017   MIT  

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    Award type:International academic award (Japan or overseas)  Country:United States

  2. 日本化学会学術賞

    2016   日本化学会  

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    Country:Japan

  3. Mukaiyama Award

    2015   有機合成化学協会  

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    Country:Japan

  4. 日本学術振興会賞

    2012   日本学術振興会  

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    Country:Japan

  5. 文部科学大臣表彰若手科学者賞

    2005   文部科学省  

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    Country:Japan

  6. 日本化学会進歩賞

    2002   日本化学会  

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    Country:Japan

  7. Merck-Karl Pfister Visiting Professorship

    2017   MIT  

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    Country:United States

  8. 有機合成化学協会 DIC・機能性材料賞

    2009   有機合成化学協会  

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    Country:Japan

  9. 第4回野副記念奨励賞

    2008.10   基礎有機化学討論会 野副記念奨励賞委員会  

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    Country:Japan

  10. 科学技術・政策研究所「ナイスステップな研究者2008」

    2008   科学技術・政策研究所  

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    Country:Japan

  11. ゴールド・メダル 東京テクノ・フォーラム21賞

    2007   東京テクノ・フォーラム  

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    Country:Japan

  12. ケイ素化学協会奨励賞

    1999   ケイ素化学協会  

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    Country:Japan

  13. 有機合成化学協会研究企画賞

    1997  

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    Country:Japan

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Papers 345

  1. Oxy-Borylenes as Photoreductants: Synthesis and Application in Dehalogenation and Detosylation Reactions.

    Lenz P, Oshimizu R, Klabunde S, Daniliuc CG, Mück-Lichtenfeld C, Tendyck JC, Mori T, Uhl W, Hansen MR, Eckert H, Yamaguchi S, Studer A

    Angewandte Chemie (International ed. in English)   Vol. 61 ( 42 ) page: e202209391   2022.10

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    DOI: 10.1002/anie.202209391

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  2. Olefin-Borane Interactions in Donor-π-Acceptor Fluorophores that Undergo Frustrated-Lewis-Pair-Type Reactions.

    Oshimizu R, Ando N, Yamaguchi S

    Angewandte Chemie (International ed. in English)   Vol. 61 ( 41 ) page: e202209394   2022.10

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    DOI: 10.1002/anie.202209394

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  3. Planarized Phenyldithienylboranes: Effects of the Bridging Moieties and π-Extension on the Photophysical Properties and Lewis Acidity.

    Sakai M, Mori M, Hirai M, Ando N, Yamaguchi S

    Chemistry (Weinheim an der Bergstrasse, Germany)   Vol. 28 ( 38 ) page: e202200728   2022.7

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    DOI: 10.1002/chem.202200728

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  4. Manipulation of Spin Polarization in Boron-Substituted Graphene Nanoribbons.

    Sun K, Silveira OJ, Saito S, Sagisaka K, Yamaguchi S, Foster AS, Kawai S

    ACS nano     2022.6

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    DOI: 10.1021/acsnano.2c04563

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  5. A negative-solvatochromic fluorescent probe for visualizing intracellular distributions of fatty acid metabolites.

    Kajiwara K, Osaki H, Greßies S, Kuwata K, Kim JH, Gensch T, Sato Y, Glorius F, Yamaguchi S, Taki M

    Nature communications   Vol. 13 ( 1 ) page: 2533   2022.5

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    DOI: 10.1038/s41467-022-30153-6

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  6. Photobase-Driven Excited-State Intramolecular Proton Transfer (ESIPT) in a Strapped pi-Electron System Reviewed

    Suzuki Naoya, Kubota Tomoya, Ando Naoki, Yamaguchi Shigehiro

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 28 ( 4 ) page: e202103584   2022.1

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1002/chem.202103584

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  7. Multiple resonance type thermally activated delayed fluorescence by dibenzo [1,4] azaborine derivatives.

    Bae J, Sakai M, Tsuchiya Y, Ando N, Chen XK, Nguyen TB, Chan CY, Lee YT, Auffray M, Nakanotani H, Yamaguchi S, Adachi C

    Frontiers in chemistry   Vol. 10   page: 990918   2022

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    DOI: 10.3389/fchem.2022.990918

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  8. Regio- and Stereoselective 1,2-Carboboration of Ynamides with Aryldichloroboranes Reviewed International coauthorship

    You Cai, Sakai Mika, Daniliuc Constantin G., Bergander Klaus, Yamaguchi Shigehiro, Studer Armido

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 60 ( 40 ) page: 21697 - 21701   2021.9

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1002/anie.202107647

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  9. Boron-Doped Polycyclic pi-Electron Systems with an Antiaromatic Borole Substructure That Forms Photoresponsive B-P Lewis Adducts Reviewed International coauthorship

    Ando Naoki, Yamada Takuya, Narita Hiroki, Oehlmann Niels N., Wagner Matthias, Yamaguchi Shigehiro

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 143 ( 26 ) page: 9944 - 9951   2021.7

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1021/jacs.1c04251

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  10. Late-stage functionalisation of alkyne-modified phospha-xanthene dyes: lysosomal imaging using an off–on–off type of pH probe Reviewed

    Hiroaki Ogasawara, Yoshiki Tanaka, Masayasu Taki, Shigehiro Yamaguchi

    Chemical Science   Vol. 12 ( 22 ) page: 7902 - 7907   2021.6

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Royal Society of Chemistry (RSC)  

    <p>A series of NIR-emissive phospha-xanthene dyes bearing an ethynyl group are reported. The late-stage functionalisation of the NIR dyes enables creation of multi-functionalised fluorescent probes that can be designed to target organelles of interest.</p>

    DOI: 10.1039/d1sc01705e

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  11. Donor-acceptor-acceptor-type near-infrared fluorophores that contain dithienophosphole oxide and boryl groups: effect of the boryl group on the nonradiative decay dagger Reviewed

    Yoshiaki Sugihara, Naoto Inai, Masayasu Taki, Thomas Baumgartner, Ryosuke Kawakami, Takashi Saitou, Takeshi Imamura, Takeshi Yanai, Shigehiro Yamaguchi

    CHEMICAL SCIENCE   Vol. 12 ( 18 ) page: 6333 - 6341   2021.5

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:ROYAL SOC CHEMISTRY  

    The use of donor-pi-acceptor (D-pi-A) skeletons is an effective strategy for the design of fluorophores with red-shifted emission. In particular, the use of amino and boryl moieties as the electron-donating and -accepting groups, respectively, can produce dyes that exhibit high fluorescence and solvatochromism. Herein, we introduce a dithienophosphole P-oxide scaffold as an acceptor-spacer to produce a boryl- and amino-substituted donor-acceptor-acceptor (D-A-A) pi-system. The thus obtained fluorophores exhibit emission in the near-infrared (NIR) region, while maintaining high fluorescence quantum yields even in polar solvents (e.g. lambda(em) = 704 nm and phi(F) = 0.69 in CH3CN). A comparison of these compounds with their formyl- or cyano-substituted counterparts demonstrated the importance of the boryl group for generating intense emission. The differences among these electron-accepting substituents were examined in detail using theoretical calculations, which revealed the crucial role of the boryl group in lowering the nonradiative decay rate constant by decreasing the non-adiabatic coupling in the internal conversion process. The D-A-A framework was further fine-tuned to improve the photostability. One of these D-A-A dyes was successfully used in bioimaging to visualize the blood vessels of Japanese medaka larvae and mouse brain.

    DOI: 10.1039/d1sc00827g

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  12. Dual Trapping of a Metastable Planarized Triarylborane pi-System Based on Folding and Lewis Acid-Base Complexation for Seeded Polymerization Reviewed

    Heekyoung Choi, Soichiro Ogi, Naoki Ando, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 143 ( 7 ) page: 2953 - 2961   2021.2

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER CHEMICAL SOC  

    We report the kinetically controlled supramolecular polymerization of boron-containing p-conjugated molecules, which was enabled by a seeding method based on dual trapping of a metastable state by synergistic intramolecular hydrogen bonding and Lewis acid-based complexation. Planarized triarylborane-based 1, which bears a diamide chain with chiral alkyl groups, was synthesized. Upon cooling, the solution of monomer 1 afforded a supramolecular polymerization in a cooperative manner to form helical supramolecular nanostructures with intense J-type aggregate emission. In the presence of pyridine, the triarylborane moiety formed a Lewis acid-base complex, which enhances the stabilization of the metastable monomeric state. An assembly incompetent structure with a folded diamide chain conformation and a pyridine moiety axially coordinated to the boron atom is responsible for slowing the spontaneous aggregation. The seeding method was successfully applied to the solution to produce homogeneous nanofibers even at a high (millimolar-level) concentration. This unprecedented kinetic control via dual trapping provides an effective method to achieve seed-initiated polymerization under concentrated conditions.

    DOI: 10.1021/jacs.0c13353

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  13. Fused Thiophene-S,S-dioxide-Based Super-Photostable Fluorescent Marker for Lipid Droplets Reviewed

    Masayasu Taki, Keiji Kajiwara, Eriko Yamaguchi, Yoshikatsu Sato, Shigehiro Yamaguchi

    ACS MATERIALS LETTERS   Vol. 3 ( 1 ) page: 42 - 49   2021.1

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER CHEMICAL SOC  

    Lipid droplets (LDs) are essential organelles in most eukaryotes, and tracking intracellular LD dynamics using synthetic small molecules is crucial for biological studies. However, only a limited number of fluorescent markers that satisfy all requirements, such as the selective staining of LDs, high photostability, and sufficient biocompatibility, have been developed. Herein, we report a series of donor-p-acceptor dyes based on the thiophene-containing fused polycyclic scaffold [1]benzothieno[3,2-b][1]benzothiophene (BTBT), in which either or both thiophene rings are oxidized into thiophene-S,S-dioxide to form an electron-accepting building block. Among these dyes, LAQ1 satisfied all the aforementioned requirements and allowed us to capture ultrasmall LDs on the endoplasmic reticulum (ER) membrane by stimulation emission depletion (STED) microscopy with a super-resolution below the diffraction limit of light. Moreover, the extremely high photostability of LAQ1 enabled recording the lipolysis of LDs and the concomitant lipogenesis, as well as long-term trajectory analysis of micro-LDs at the single-particle level in living cells.

    DOI: 10.1021/acsmaterialslett.0c00451

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  14. Phosphole P-Oxide-Containing pi-Electron Materials: Synthesis and Applications in Fluorescence Imaging

    Yamaguchi Shigehiro, Fukazawa Aiko, Taki Masayasu

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   Vol. 75 ( 11 ) page: 1179 - 1187   2017.11

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  15. Color-tunable fluorescent nanoparticles encapsulating trialkylsilyl-substituted pyrene liquids

    Taki Masayasu, Azeyanagi Saki, Hayashi Kenzo, Yamaguchi Shigehiro

    JOURNAL OF MATERIALS CHEMISTRY C   Vol. 5 ( 8 ) page: 2142 - 2148   2017.2

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    DOI: 10.1039/c6tc05208h

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  16. A strap strategy for construction of an excited-state intramolecular proton transfer (ESIPT) system with dual fluorescence.

    Suzuki N, Fukazawa A, Nagura K, Saito S, Kitoh-Nishioka H, Yokogawa D, Irle S, Yamaguchi S

    Angewandte Chemie (International ed. in English)   Vol. 53 ( 31 ) page: 8231 - 5   2014.7

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    DOI: 10.1002/anie.201404867

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  17. Regioselective Unsymmetrical Tetraallylation of C-60 through Palladium Catalysis

    Nambo Masakazu, Wakamiya Atsushi, Yamaguchi Shigehiro, Itami Kenichiro

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 131 ( 42 ) page: 15112 - +   2009.10

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  18. Design and synthesis of boron-containing functional pi-electron materials

    Wakamiya Atsushi, Yamaguchi Shigehiro

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   Vol. 66 ( 9 ) page: 858 - 868   2008.9

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  19. Crystallographic and chiroptical studies on tetraarylferrocenes for use as chiral rotary modules for molecular machines.

    Muraoka T, Kinbara K, Wakamiya A, Yamaguchi S, Aida T

    Chemistry (Weinheim an der Bergstrasse, Germany)   Vol. 13 ( 6 ) page: 1724 - 30   2007

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    DOI: 10.1002/chem.200601098

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  20. Boron as a key component for new pi-electron materials

    Yamaguchi Shigehiro, Wakamiya Atsushi

    PURE AND APPLIED CHEMISTRY   Vol. 78 ( 7 ) page: 1413 - 1424   2006.7

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    DOI: 10.1351/pac200678071413

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  21. Bis-silicon-bridged stilbene homologues synthesized by new intramolecular reductive double cyclization

    Yamaguchi S, Xu CH, Tamao K

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 125 ( 45 ) page: 13662 - 13663   2003.11

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  22. Fluorescent Organic pi-Radicals Stabilized with Boron: Featuring a SOMO-LUMO Electronic Transition

    Masato Ito, Shusuke Shirai, Yongfa Xie, Tomokatsu Kushida, Naoki Ando, Hiroki Soutome, Kazuhiro J. Fujimoto, Takeshi Yanai, Kenichi Tabata, Yasuo Miyata, Hiroshi Kita, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 61 ( 25 ) page: e202201965   2022.6

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:WILEY-V C H VERLAG GMBH  

    We report on the fluorescence properties of a new class of emissive and stable pi-radicals that contain a boron atom at a position distant from the radical center. A fully planarized derivative exhibited an intense red fluorescence with high fluorescence quantum yields (Phi(F) > 0.67) even in polar solvents. To elucidate the origin of this phenomenon, we synthesized another boron-stabilized radical that contains a bulky aryl group on the boron atom. A comparison of these derivatives, as well as with conventional donor-rr-acceptor (D-pi-A)-type emissive pi-radicals, unveiled several characteristic features in their photophysical properties. A theoretical analysis revealed that the SOMO-LUMO electronic transition generates an emissive D-1 state. Unlike conventional D-pi-A-type pi-radicals, this state does not undergo significant structural relaxation. The boron-stabilized pi-radicals demonstrated promising potential for organic light-emitting diodes as an emitting material.

    DOI: 10.1002/anie.202201965

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  23. Late-stage modification of π-electron systems based on asymmetric oxidation of a medium-sized sulfur-containing ring Reviewed

    Masahiro Hayakawa, Satoshi Horike, Yuh Hijikata, Kosuke Yasui, Shigehiro Yamaguchi, Aiko Fukazawa

    Chemical Communications   Vol. 58 ( 15 ) page: 2548 - 2551   2022.2

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Royal Society of Chemistry (RSC)  

    The asymmetric oxidation of a sulfur-containing nine-membered heterocycle was achieved for the late-stage introduction of chirality to the substituents of π-electron systems.

    DOI: 10.1039/d1cc06996a

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  24. Fully fused boron-doped polycyclic aromatic hydrocarbons: their synthesis, structure-property relationships, and self-assembly behavior in aqueous media Reviewed

    Hiroki Narita, Heekyoung Choi, Masato Ito, Naoki Ando, Soichiro Ogi, Shigehiro Yamaguchi

    CHEMICAL SCIENCE   Vol. 13 ( 5 ) page: 1484 - 1491   2022.2

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:ROYAL SOC CHEMISTRY  

    Planarized triarylboranes are attracting increasing attention not only as models of boron-doped graphenes, but also as promising materials for organic optoelectronics. In particular, polycyclic aromatic hydrocarbon (PAH) skeletons with embedded boron atom(s) in the inner positions are of importance in light of their high chemical stability and pi-stacking ability derived from their planar geometries. Herein, we disclose a robust synthesis of such fully fused boron-doped PAHs and their self-assembly behavior in aqueous media to explore their potential utility in biological applications. The synthesis using in situ-generated planar diarylboranes as a key precursor afforded a series of fully fused boron-doped PAHs, even including an amphiphilic derivative with hydrophilic side chains. These compounds exhibited red emission in solution, and slight structural modification resulted in increased fluorescence brightness. While these compounds showed relatively low Lewis acidity compared to their partially ring-fused counterparts, their Lewis acidities were slightly increased in polar solvents compared to those in nonpolar solvents. In addition, their B-N Lewis acid-base adducts, even those with a strong, charge-neutral Lewis base such as N,N-dimethylaminopyridine (DMAP), exhibited photo-dissociation behavior in the excited state. The amphiphilic derivative showed significant spectral changes with increased water content in DMSO/H2O mixed media and formed sheet-like aggregates. The disassembly and assembly processes of the aggregates were externally controlled by the addition of DMAP and an acid, accompanied by a change in the fluorescence intensity.

    DOI: 10.1039/d1sc06710a

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  25. A Supramolecular Polymer Constituted of Antiaromatic Ni II Norcorroles Reviewed

    Shusaku Ukai, Aiko Takamatsu, Masaki Nobuoka, Yusuke Tsutsui, Norihito Fukui, Soichiro Ogi, Shu Seki, Shigehiro Yamaguchi, Hiroshi Shinokubo

    Angewandte Chemie International Edition   Vol. 61 ( 6 ) page: e202114230   2022.2

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Wiley  

    DOI: 10.1002/anie.202114230

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    Other Link: https://onlinelibrary.wiley.com/doi/full-xml/10.1002/anie.202114230

  26. Bridging pico-to-nanonewtons with a ratiometric force probe for monitoring nanoscale polymer physics before damage. Reviewed International journal

    Ryota Kotani, Soichi Yokoyama, Shunpei Nobusue, Shigehiro Yamaguchi, Atsuhiro Osuka, Hiroshi Yabu, Shohei Saito

    Nature communications   Vol. 13 ( 1 ) page: 303 - 303   2022.1

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    Understanding the transmission of nanoscale forces in the pico-to-nanonewton range is important in polymer physics. While physical approaches have limitations in analyzing the local force distribution in condensed environments, chemical analysis using force probes is promising. However, there are stringent requirements for probing the local forces generated before structural damage. The magnitude of those forces corresponds to the range below covalent bond scission (from 200 pN to several nN) and above thermal fluctuation (several pN). Here, we report a conformationally flexible dual-fluorescence force probe with a theoretically estimated threshold of approximately 100 pN. This probe enables ratiometric analysis of the distribution of local forces in a stretched polymer chain network. Without changing the intrinsic properties of the polymer, the force distribution was reversibly monitored in real time. Chemical control of the probe location demonstrated that the local stress concentration is twice as biased at crosslinkers than at main chains, particularly in a strain-hardening region. Due to the high sensitivity, the percentage of the stressed force probes was estimated to be more than 1000 times higher than the activation rate of a conventional mechanophore.

    DOI: 10.1038/s41467-022-27972-y

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  27. Pro-tumoral behavior of omental adipocyte-derived fibroblasts in tumor microenvironment at the metastatic site of ovarian cancer Reviewed

    Iyoshi Shohei, Yoshihara Masato, Nakamura Kae, Sugiyama Mai, Koya Yoshihiro, Kitami Kazuhisa, Uno Kaname, Mogi Kazumasa, Tano Sho, Tomita Hiroyuki, Kajiwara Keiji, Taki Masayasu, Yamaguchi Shigehiro, Nawa Akihiro, Kajiyama Hiroaki

    INTERNATIONAL JOURNAL OF CANCER   Vol. 149 ( 11 ) page: 1961 - 1972   2021.12

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    DOI: 10.1002/ijc.33770

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  28. Extended π-Electron Delocalization in Quinoid-Based Conjugated Polymers Boosts Intrachain Charge Carrier Transport

    Tsubasa Mikie, Masahiro Hayakawa, Kenta Okamoto, Keitaro Iguchi, Shuhei Yashiro, Tomoyuki Koganezawa, Masatomo Sumiya, Hiroyuki Ishii, Shigehiro Yamaguchi, Aiko Fukazawa, Itaru Osaka

    Chemistry of Materials   Vol. 33 ( 21 ) page: 8183 - 8193   2021.11

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society (ACS)  

    DOI: 10.1021/acs.chemmater.1c02072

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  29. Electron-Deficient Heteroacenes that Contain Two Boron Atoms: Near-Infrared Fluorescence Based on a Push-Pull Effect** Reviewed

    Masato Ito, Mika Sakai, Naoki Ando, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 60 ( 40 ) page: 21853 - 21859   2021.9

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:WILEY-V C H VERLAG GMBH  

    Electron-deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of silicon-bridged precursors. X-ray crystallographic analysis revealed quinoidal structures, which give rise to two-step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near-infrared (NIR) region. These properties originate from the push-pull effect along the long axis of the molecule derived from the electron-donating ether moieties and the electron-accepting boron moieties. Of particular note is the NIR emission of the thienothiophene-centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm(-1) in cyclohexane. A Franck-Condon analysis revealed the crucial role of the sterically less-hindered thienothiophene spacer in achieving this sharp emission band.

    DOI: 10.1002/anie.202106642

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  30. Excited-state conformation capture by supramolecular chains towards triplet-involved organic emitters Reviewed International coauthorship

    Liu Hao, Ando Naoki, Yamaguchi Shigehiro, Naumov Pance, Zhang Hongyu

    CHINESE CHEMICAL LETTERS   Vol. 32 ( 5 ) page: 1669 - 1674   2021.5

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  31. Organic phosphorescent polymorphs induced by various halogen bonds with stimuli-responsive single/dual phosphorescence switching Reviewed International coauthorship

    Hao Liu, Wentao Liu, Naoki Ando, Shigehiro Yamaguchi, Hongyu Zhang

    JOURNAL OF MATERIALS CHEMISTRY C   Vol. 9 ( 8 ) page: 2738 - 2743   2021.2

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ROYAL SOC CHEMISTRY  

    Herein, we report the first example of two pure organic polymorphs with stimuli-responsive single/dual phosphorescence transformation. By analyzing the crystal structures and theoretical results, it could be understood that efficient intermolecular interactions could restrict the molecular movements and lock distinct molecular conformations, leading to different phosphorescence behaviors. Besides, single/dual phosphorescence could transform into each other by heating or under solvent vapor conditions. Considering such unique properties, logical sensors (AND gate and OR gate) were built by providing different emission colors as inputs. Our work provides not only important information for understanding the dual RTP mechanism but also unique stimuli-responsive pure organic phosphorescent materials to enrich material fields.

    DOI: 10.1039/d0tc05468b

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  32. Twofold C-H Activation Enables Synthesis of a Diazacoronene-Type Fluorophore with Near Infrared Emission Through Isosteric Replacement Reviewed International coauthorship

    Steffen Gressies, Masato Ito, Mika Sakai, Hiroshi Osaki, Ju Hyun Kim, Tobias Gensch, Constantin Daniliuc, Naoki Ando, Shigehiro Yamaguchi, Frank Glorius

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 27 ( 8 ) page: 2753 - 2759   2021.2

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:WILEY-V C H VERLAG GMBH  

    The synthesis and photophysical properties of a soluble amide-embedded coronene is reported. The key step in this synthesis is the twofold C-H activation of diazaperylene by a rhodium(III)Cp* catalyst. This unprecedented structural motif shows intense fluorescence in the near infrared region with a small Stokes shift and a distinct vibronic structure, which exhibits a slight extent of negative solvatochromism. Comparison of this compound with some relevant compounds revealed the importance of the amide incorporation in the peripheral concave region including an angular position to retain high aromaticity reflecting that of parent coronene. Treatment of this compound with Lewis acid B(C6F5)(3) formed a bis-adduct, which exhibited enhanced aromaticity as a consequence of the increased double bond character of the amide C-N bonds.

    DOI: 10.1002/chem.202004080

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  33. Dithieno[a,e]pentalenes: Highly Antiaromatic Yet Stable pi-Electron Systems without Bulky Substituents Reviewed

    Junichi Usuba, Masahiro Hayakawa, Shigehiro Yamaguchi, Aiko Fukazawa

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 27 ( 5 ) page: 1482 - 1482   2021.1

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  34. Dithieno[a,e]pentalenes: Highly Antiaromatic Yet Stable pi-Electron Systems without Bulky Substituents

    Junichi Usuba, Masahiro Hayakawa, Shigehiro Yamaguchi, Aiko Fukazawa

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 27 ( 5 ) page: 1638 - 1647   2021.1

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    Dithieno[a,e]penalenes (DTPs) with various substituents were synthesized as a class of antiaromatic compounds. Annulation of thiophene rings imparts the pentalene moiety with high thermal stability even without bulky substituents, while retaining antiaromaticity. The higher magnitude of antiaromaticity in DTPs, in addition to the differences in the electronic structures of the fused aromatic rings, resulted in a narrower HOMO-LUMO gap than that of the corresponding dibenzo[a,e]pentalene analog, giving rise to red-shifted electronic absorption that reaches the near-infrared region. Moreover, systematic investigations on the solid-state packing structure revealed that DTPs prefer offset face-to-face packing motifs rather than face-centered pi-pi stacking. In particular, the thienyl-substituted DTP bearing hydrophilic side chains exhibited thermochromic behavior in polar solvents, which was ascribed to the formation of aggregates.

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  35. Letters from Japan: Characteristic Approaches to Contemporary Organic Chemistry

    Shigehiro Yamaguchi

    ORGANIC LETTERS   Vol. 22 ( 24 ) page: 9406 - 9407   2020.12

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    DOI: 10.1021/acs.orglett.0c03771

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  36. Hydrophobicity-driven folding and seeded polymerization of cystine-based dimeric diamides in aqueous media

    Natsumi Fukaya, Soichiro Ogi, Midori Kawashiro, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 56 ( 85 ) page: 12901 - 12904   2020.11

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    Seeded supramolecular polymerization of cystine-based dimeric diamides with aromatic substituents at the C- and N-termini was achieved in aqueous media. Theoretical and spectroscopic studies reveal that the terminal groups play crucial roles in slowing spontaneous assembly through formation of a folded conformation and guiding molecular alignment in the aggregated state.

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  37. Covalent Self-Labeling of Tagged Proteins with Chemical Fluorescent Dyes in BY-2 Cells and Arabidopsis Seedlings([OPEN])

    Ryu J. Iwatate, Akira Yoshinari, Noriyoshi Yagi, Marek Grzybowski, Hiroaki Ogasawara, Mako Kamiya, Toru Komatsu, Masayasu Taki, Shigehiro Yamaguchi, Wolf B. Frommer, Masayoshi Nakamura

    PLANT CELL   Vol. 32 ( 10 ) page: 3081 - 3094   2020.10

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    Synthetic chemical fluorescent dyes promise to be useful for many applications in biology. Covalent, targeted labeling, such as with a SNAP-tag, uses synthetic dyes to label specific proteins in vivo for studying processes such as endocytosis or for imaging via super-resolution microscopy. Despite its potential, such chemical tagging has not been used effectively in plants. A major drawback has been the limited knowledge regarding cell wall and membrane permeability of the available synthetic dyes. Of 31 synthetic dyes tested here, 23 were taken up into BY-2 cells, while eight were not. This creates sets of dyes that can serve to measure endocytosis. Three of the dyes that were able to enter the cells, SNAP-tag ligands of diethylaminocoumarin, tetramethylrhodamine, and silicon-rhodamine 647, were used to SNAP-tag alpha-tubulin. Successful tagging was verified by live cell imaging and visualization of microtubule arrays in interphase and during mitosis in Arabidopsis (Arabidopsis thaliana) seedlings. Fluorescence activation-coupled protein labeling with DRBG-488 was used to observe PIN-FORMED2 (PIN2) endocytosis and delivery to the vacuole as well as preferential delivery of newly synthesized PIN2 to the actively forming cell plate during mitosis. Together, the data demonstrate that specific self-labeling of proteins can be used effectively in plants to study a wide variety of cellular and biological processes.Multicolor imaging with SNAP-tagged tubulin and monitoring of PIN2 endocytosis with a chemical dye demonstrate that specific self-labeling of proteins can be used effectively in plants.

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  38. Magnetism of Topological Boundary States Induced by Boron Substitution in Graphene Nanoribbons

    Niklas Friedrich, Pedro Brandimarte, Jingcheng Li, Shohei Saito, Shigehiro Yamaguchi, Iago Pozo, Diego Pena, Thomas Frederiksen, Aran Garcia-Lekue, Daniel Sanchez-Portal, Jose Ignacio Pascual

    PHYSICAL REVIEW LETTERS   Vol. 125 ( 14 ) page: 146801   2020.9

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    Graphene nanoribbons (GNRs), low-dimensional platforms for carbon-based electronics, show the promising perspective to also incorporate spin polarization in their conjugated electron system. However, magnetism in GNRs is generally associated with localized states around zigzag edges, difficult to fabricate and with high reactivity. Here we demonstrate that magnetism can also be induced away from physical GNR zigzag edges through atomically precise engineering topological defects in its interior. A pair of substitutional boron atoms inserted in the carbon backbone breaks the conjugation of their topological bands and builds two spin-polarized boundary states around them. The spin state was detected in electrical transport measurements through boron-substituted GNRs suspended between the tip and the sample of a scanning tunneling microscope. First-principle simulations find that boron pairs induce a spin 1, which is modified by tuning the spacing between pairs. Our results demonstrate a route to embed spin chains in GNRs, turning them into basic elements of spintronic devices.

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  39. Long-Lived Charge-Transfer State from B-N Frustrated Lewis Pairs Enchained in Supramolecular Copolymers

    Beatrice Adelizzi, Pongphak Chidchob, Naoki Tanaka, Brigitte A. G. Lamers, Stefan C. J. Meskers, Soichiro Ogi, Anja R. A. Palmans, Shigehiro Yamaguchi, E. W. Meijer

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 142 ( 39 ) page: 16681 - 16689   2020.9

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    The field of supramolecular polymers is rapidly expanding; however, the exploitation of these systems as functional materials is still elusive. To become competitive, supramolecular polymers must display microstructural order and the emergence of new properties upon copolymerization. To tackle this, a greater understanding of the relationship between monomers' design and polymer microstructure is required as well as a set of functional monomers that efficiently interact with one another to synergistically generate new properties upon copolymerization. Here, we present the first implementation of frustrated Lewis pairs into supramolecular copolymers. Two supramolecular copolymers based on p-conjugated O-bridged triphenylborane and two different triphenylamines display the formation of B-N pairs within the supramolecular chain. The remarkably long lifetime and the circularly polarized nature of the resulting photoluminescence emission highlight the possibility to obtain an intermolecular B-N charge transfer. These results are proposed to be the consequences of the enchainment of B-N frustrated Lewis pairs within 1D supramolecular aggregates. Although it is challenging to obtain a precise molecular picture of the copolymer microstructure, the formation of random blocklike copolymers could be deduced from a combination of optical spectroscopic techniques and theoretical simulation.

    DOI: 10.1021/jacs.0c06921

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  40. A Near-Infrared Emissive pi-Conjugated Polymer Consisting of an Excited-State Intramolecular Proton Transfer Unit

    Naoya Suzuki, Masayuki Wakioka, Fumiyuki Ozawa, Shigehiro Yamaguchi

    ASIAN JOURNAL OF ORGANIC CHEMISTRY   Vol. 9 ( 9 ) page: 1326 - 1332   2020.9

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    Near infrared (NIR)-emissive polymers are attractive luminescent materials due to their utilities in biological, optoelectronic, and telecommunication applications. Herein we report the use of a dialkylamine-strapped dithienylpyrrole (DTP) as an excited-state intramolecular proton transfer (ESIPT) building block for producing NIR-emissive pi-conjugated polymers. The study of a series of model compounds showed that the extension of pi-conjugation with a moderately electron-accepting comonomer unit, dithientyl-substituted thiazolo[5,4-d]thiazole (TzTz), effectively stabilizes the zwitterionic ESIPT state while increasing the oscillator strength for the electronic transition from the ESIPT state. Consequently, a polymer consisted of DTP and TzTz units exhibited a significantly red-shifted emission, exceeding 750 nm, from the ESIPT state in polar solvents.

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  41. Phosphole-Oxide-Based Fluorescent Probe for Super-resolution Stimulated Emission Depletion Live Imaging of the Lysosome Membrane

    Chenguang Wang, Masayasu Taki, Keiji Kajiwara, Junwei Wang, Shigehiro Yamaguchi

    ACS MATERIALS LETTERS   Vol. 2 ( 7 ) page: 705 - 711   2020.7

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    Super-resolution imaging techniques have become increasingly important tools to visualize suborganelle structures and dynamic processes in living cells on the nanoscale. However, the utility of these imaging techniques is currently limited by the availability of advanced fluorescent probes that enable the specific labeling of the organelle of interest and provide the absorption/emission properties required for super-resolution imaging techniques. Herein, LysoPB Yellow is presented as a new small-molecule fluorescent probe that can selectivity stain the lysosomal membrane. Its outstandingly high photostability and long fluorescence lifetime are beneficial for its use in super-resolution stimulated emission depletion (STED) microscopy. A lysosomal membrane stained with LysoPB Yellow was successfully visualized by STED imaging in living cells with a full width at half maximum (FWHM) of 70 nm, which is substantially below the diffraction limit of light. Additionally, LysoPB Yellow displayed excellent retention ability and negligible cytotoxicity. Consequently, long-term time-lapse confocal imaging of living cells was successfully conducted, which demonstrates the practical utility of LysoPB Yellow in fluorescence imaging.

    DOI: 10.1021/acsmaterialslett.0c00147

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  42. Effects of Amino Group Substitution on the Photophysical Properties and Stability of Near-Infrared Fluorescent P-Rhodamines

    Marek Grzybowski, Masayasu Taki, Keiji Kajiwara, Shigehiro Yamaguchi

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 26 ( 35 ) page: 7912 - 7917   2020.6

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    A series of phosphine oxide-bridged rhodamines (P-rhodamines) bearing various acyclic and cyclic amine moieties, including dimethyl- and diethylamine, azetidine, pyrrolidine and 7-azabicyclo[2,2,1]heptane (7ABH), have been synthesized. The photophysical properties as well as chemical and photostability of these dyes have been studied in detail. Among these dyes, the 7ABH-substituted dye shows stronger fluorescence in the near-infrared (NIR) region, relative to the other P-rhodamines. This dye could be applied to live-cell imaging, wherein lysosomes were selectively stained in a pH-independent manner. It was also found that the ring fusion of the amine moieties gives rise to remarkably redshifted spectra, with absorption and emission maxima at 770 and 820 nm, respectively, spectrally close to that of indocyanine green (ICG). Importantly, the ring-fused P-rhodamines showed much higher photostability than ICG, indicative of their promising utility as the NIR-emissive dyes.

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  43. Multistep Photoisomerization of Dimesitylboron-Functionalized Stilbene Analogues

    Yuxin Ge, Naoki Ando, Lijie Liu, Xiang Wang, Francoise Sauriol, Shigehiro Yamaguchi, Gang Wu, Suning Wang

    ORGANIC LETTERS   Vol. 22 ( 8 ) page: 3258 - 3262   2020.4

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    Dimesitylboron-functionalized stilbene derivatives have been found to undergo an unusual regioselective photoisomerization upon irradiation at 365 nm. Using NMR to follow the photoreaction, the structures of key reaction intermediates and the final products were established. This photoisomerization occurs in four steps: trans-cis isomerization, Diels-Alder reaction, di-pi-methane rearrangement, and ring opening with [1,3]-H migration. This results in the formation of a rare structure with three fused five-membered rings and a six-membered one.

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  44. Donor-Acceptor Materials Exhibiting Thermally Activated Delayed Fluorescence Using a Planarized N-Phenylbenzimidazole Acceptor

    Ethan R. Sauve, Jaesuk Paeng, Shigehiro Yamaguchi, Zachary M. Hudson

    JOURNAL OF ORGANIC CHEMISTRY   Vol. 85 ( 1 ) page: 108 - 117   2020.1

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    An N-phenylbenzimidazole constrained in a coplanar fashion with a methylene tether (IMAC) was designed and used to prepare a series of emitters exhibiting thermally activated delayed fluorescence (TADF). Four novel TADF emitters using 9,9-dimethylacridine, phenoxazine, phenothiazine, and bis(di-ptolylamino)carbazole as the donor group were designed and synthesized using IMAC as the acceptor. Additionally, two deepblue fluorescent emitters were prepared with carbazole and tercarbazole as the donor moieties. The twisted conformation between donor and acceptor in these molecules resulted in effective spatial separation of the HOMO and LUMO and small singlet-triplet energy gaps. Crystallographic properties, electronic structures, thermal stabilities, photophysical properties, and energy levels were studied systematically. Ultimately, these findings provide a promising opportunity for the design and synthesis of highly efficient TADF materials based on IMAC derivatives.

    DOI: 10.1021/acs.joc.9b02283

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  45. Hydrophobicity and CH/pi-interaction-driven self-assembly of amphiphilic aromatic hydrocarbons into nanosheets Reviewed

    Tsuyoshi Nishikawa, Hiroki Narita, Soichiro Ogi, Yoshikatsu Sato, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 55 ( 99 ) page: 14950 - 14953   2019.12

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    The hydrophobicity and CH/pi-interaction-driven self-assembly of an amphiphile that contains a biphenylanthracene group furnishes two-dimensional aggregates in dilute aqueous solution. A windmill-shaped molecular packing structure that arises from multiple intermolecular CH/pi interactions of the aromatic hydrocarbons is the key motif for the self-assembly into micrometer-scale nanosheets.

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  46. [eta(5)-Cp*B-Mes](+): A Masked Potent Boron Lewis Acid

    Hsi-Ching Tseng, Chao-Tang Shen, Kentaro Matsumoto, Ding-Nan Shih, Yi-Hung Liu, Shie-Ming Peng, Shigehiro Yamaguchi, Ya-Fan Lin, Ching-Wen Chiu

    ORGANOMETALLICS   Vol. 38 ( 22 ) page: 4516 - 4521   2019.11

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    The chemistry of the boron cation has been revitalized in the past decade due to its newfound application in stoichiometric and catalytic organic reactions. To extend the frontier of boron cation catalysis, we came to discover that a mesityl-substituted eta(5)-Cp*-coordinated boron cation could serve as a powerful Lewis acid for organic catalytic transformations. The boron cation [Cp*B-Mes][B(C6F5)(4)] ([1] [B(C6F5)(4)]) stabilized in a boronium-like electronic structure binds to Et3PO readily and displays an acceptor number exceeding that of B(C6F5)(3) on the Gutmann-Beckett acidity scale. The steric and electronic stabilization exerted by the electron-donating Cp* renders the highly Lewis acidic boron cation an easy-to-handle catalyst for hydrodeoxygenation of aryl ketones at ambient temperature. The exceptional catalytic performance of [1](+) implies that the incorporation of a coordinatively flexible substituent at boron is critical in bringing catalytic activity and stability to boron cation catalysts.

    DOI: 10.1021/acs.organomet.9b00671

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  47. The Effect of Branching on the One- and Two-Photon Absorption, Cell Viability, and Localization of Cationic Triarylborane Chromophores with Dipolar versus Octupolar Charge Distributions for Cellular Imaging Reviewed

    Stefanie Griesbeck, Evripidis Michail, Florian Rauch, Hiroaki Ogasawara, Chenguang Wang, Yoshikatsu Sato, Robert M. Edkins, Zuolun Zhang, Masayasu Taki, Christoph Lambert, Shigehiro Yamaguchi, Todd B. Marder

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 25 ( 57 ) page: 13164 - 13175   2019.10

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    Two different chromophores, namely a dipolar and an octupolar system, were prepared and their linear and nonlinear optical properties as well as their bioimaging capabilities were compared. Both contain triphenylamine as the donor and a triarylborane as the acceptor, the latter modified with cationic trimethylammonio groups to provide solubility in aqueous media. The octupolar system exhibits a much higher two-photon brightness, and also better cell viability and enhanced selectivity for lysosomes compared with the dipolar chromophore. Furthermore, both dyes were applied in two-photon excited fluorescence (TPEF) live-cell imaging.

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  48. Near-infrared fluorescein dyes containing a tricoordinate boron atom

    Naoki Ando, Hiroki Soutome, Shigehiro Yamaguchi

    CHEMICAL SCIENCE   Vol. 10 ( 33 ) page: 7816 - 7821   2019.9

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    Bora-fluoresceins (BFs), fluorescein analogues containing a tricoordinate boron atom instead of an oxygen atom at the 10-position of the fluorescein skeleton, were synthesized as a new family of fluorescein analogues. The deprotonated BFs exhibited absorption and fluorescence in the near-infrared region, which were significantly red-shifted relative to those of hitherto-known heteroatom-substituted fluorescein analogues on account of the orbital interaction between the tricoordinate boron atom and the fluorescein skeleton. BFs also showed multi-stage changes resulting from a Lewis acid-base equilibrium at the boron center in combination with a Bronsted acid-base equilibrium at the phenolic hydroxy group.

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  49. Monitoring Fluorescence Response of Amphiphilic Flapping Molecules in Compressed Monolayers at the Air-Water Interface Reviewed

    Waka Nakanishi, Shohei Saito, Naoki Sakamoto, Akihiro Kashiwagi, Shigehiro Yamaguchi, Hideki Sakai, Katsuhiko Ariga

    CHEMISTRY-AN ASIAN JOURNAL   Vol. 14 ( 16 ) page: 2869 - 2876   2019.8

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    The air-water interface, which is the boundary of two phases with a large difference in polarity, gives a distinct environment compared with bulk water or air. Since the interface provides a field for various biomolecules to work, it is important to understand the molecular behaviors at the interface. Here, polarity-independent flapping viscosity probes (FLAP) equipped with hydrophobic/hydrophilic substituents have been synthesized and studied at the air-water interface. In situ fluorescence (FL), which is related to the internal motion and orientation, of three different FLAPs were investigated at the interface, and the internal motion of the molecule was indicated to be suppressed at the interface. In addition, the molecular response was compared with that of conventional viscosity probes (molecular rotors), which indicates the different behaviors of FLAP probably due to the distinct molecular orientation as well as molecular motion.

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  50. A photostable fluorescent marker for the superresolution live imaging of the dynamic structure of the mitochondrial cristae Reviewed International journal

    Chenguang Wang, Masayasu Taki, Yoshikatsu Sato, Yasushi Tamura, Hideyuki Yaginuma, Yasushi Okada, Shigehiro Yamaguchi

    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA   Vol. 116 ( 32 ) page: 15817 - 15822   2019.8

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    Stimulation emission depletion (STED) microscopy enables ultrastructural imaging of organelle dynamics with a high spatiotemporal resolution in living cells. For the visualization of the mitochondria! membrane dynamics in STED microscopy, rationally designed mitochondrial fluorescent markers with enhanced photostability are required. Herein, we report the development of a superphotostable fluorescent labeling reagent with long fluorescence lifetime, whose design is based on a structurally reinforced naphthophosphole fluorophore that is conjugated with an electron-donating diphenylamino group. The combination of long-lived fluorescence and superphotostable features of the fluorophore allowed us to selectively capture the ultrastructures of the mitochondria! cristae with a resolution of similar to 60 nm when depleted at 660 nm. This chemical tool provides morphological information of the cristae, which has so far only been observed in fixed cells using electron microscopy. Moreover, this method gives information about the dynamic ultrastructures such as the intermembrane fusion in different mitochondria as well as the intercristae mergence in a single mitochondrion during the apoptosis-like mitochondrial swelling process.

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  51. Structurally Constrained Boron-, Nitrogen-, Silicon-, and Phosphorus-Centered Polycyclic pi-Conjugated Systems

    Masato Hirai, Naoki Tanaka, Mika Sakai, Shigehiro Yamaguchi

    CHEMICAL REVIEWS   Vol. 119 ( 14 ) page: 8291 - 8331   2019.7

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    Incorporation of main group elements into the it-conjugated frameworks is a sophisticated strategy to alter the fundamental nature of the parent conjugated pi systems, giving rise to attractive electronic and photophysical properties that are otherwise inaccessible with classic carbon- or metal-based materials. Out of all irconjugated heterocycles, those that are structurally constrained by tethered aryl substituents surrounding the main group center deserve a great deal of attention because not only do they commonly possess the maximum efficiency of it -conjugation and intermolecular interaction, but they also enjoy remarkable thermal and morphological stabilities that are especially crucial for solid-state performances. In certain cases, elucidation of the behavior of such compounds may additionally provide sufficient perspective toward graphene materials doped with main group elements, which are widely considered as potential next -generation optoelectronic materials. In this review, we will specifically focus on historical developments of structurally constrained polycyclic it -electron systems particularly of those with boron, nitrogen, silicon, or phosphorus atoms annulated directly into the center of 2r -conjugated systems.

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  52. Planarized B,N-phenylated dibenzoazaborine with a carbazole substructure: electronic impact of the structural constraint

    Mikinori Ando, Mika Sakai, Naoki Ando, Masato Hirai, Shigehiro Yamaguchi

    ORGANIC & BIOMOLECULAR CHEMISTRY   Vol. 17 ( 22 ) page: 5500 - 5504   2019.6

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    A B,N-diphenyl-5,10-dihydro-dibenzo-1,4-azaborine, in which both phenyl groups on the boron and nitrogen atoms are planarized to generate a carbazole substructure, was synthesized. The structral constraint around the boron and nitrogen atoms alters the pi-conjugation mode and thus the photophysical and electrochemical properties. Specifically, this structurally constrained dibenzoazaborine showed an intense blue emission with a narrow full width at half maximum. One of its derivatives exhibited near infrared absorption in the one-electron-oxidized state.

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  53. Optimization of Aqueous Stability versus pi-Conjugation in Tetracationic Bis(triarylborane) Chromophores: Applications in Live-Cell Fluorescence Imaging

    Stefanie Griesbeck, Matthias Ferger, Corinna Czernetzi, Chenguang Wang, Ruediger Bertermann, Alexandra Friedrich, Martin Haehnel, Daniel Sieh, Masayasu Taki, Shigehiro Yamaguchi, Todd B. Marder

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 25 ( 32 ) page: 7679 - 7688   2019.6

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    The stability of tetracationic triarylboranes in dilute aqueous solution was investigated by tuning the steric demand of the linker in a (para-(N,N,N-trimethylammonio)xylyl)(2)B-(linker)-B(para-(N,N,N-trimethylammonio)xylyl)(2) structure. With increasing steric bulk of the linker, namely 1,4-phenylene, 2,2 '''-(3,3 '''-dimethyl)-5,2 ':5 ',2 '':5 '',5 '''-quaterthiophene, 9,10-anthracenylene, and 4,4 '''-(5 '-(3,5-dimethylphenyl))(5 ''-(3 ''',5 '''-dimethylphenyl))-2 ',2 ''-bithiophene, the stability of the compounds increased. The anthracene-based chromophore, compound 3M is water-stable for at least 48 h, is nontoxic to cells and exhibits an exceedingly high fluorescence quantum yield of 0.86 in water making it an ideal candidate for confocal live-cell imaging of lysosomes.

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  54. Tuning the pi-bridge of quadrupolar triarylborane chromophores for one- and two-photon excited fluorescence imaging of lysosomes in live cells

    Griesbeck Stefanie, Michail Evripidis, Wang Chenguang, Ogasawara Hiroaki, Lorenzen Sabine, Gerstner Lukas, Zang Theresa, Nitsch Joern, Sato Yoshikatsu, Bertermann Ruediger, Taki Masayasu, Lambert Christoph, Yamaguchi Shigehiro, Marder Todd B.

    CHEMICAL SCIENCE   Vol. 10 ( 20 ) page: 5405 - 5422   2019.5

  55. Seeded Polymerization of an Amide-Functionalized Diketopyrrolopyrrole Dye in Aqueous Media

    Soichiro Ogi, Natsumi Fukaya, Arifin, Bastian Bjerkem Skjelstad, Yuh Hijikata, Shigehiro Yamaguchi

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 25 ( 30 ) page: 7303 - 7307   2019.5

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    The self-assembly of an amide-functionalized dithienyldiketopyrrolopyrrole (DPP) dye in aqueous media was achieved through seed-initiated supramolecular polymerization. Temperature- and time-dependent studies showed that the spontaneous polymerization of the DPP derivative was temporally delayed upon cooling the monomer solution in a methanol/water mixture. Theoretical calculations revealed that an amide-functionalized DPP derivative adopts an energetically favorable folded conformation in the presence of water molecules due to hydration. This conformational change is most likely responsible for the trapping of monomers in the initial stage of the cooperative supramolecular polymerization in aqueous media. However, the monomeric species can selectively interact with externally added fragmented aggregates as seeds through concerted pi-stacking and hydrogen-bonding interactions. Consequently, the time course of the supramolecular polymerization and the morphology of the aggregated state can be controlled, and one-dimensional fibers that exhibit a J-aggregate-like bathochromically shifted absorption band can be obtained.

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  56. Organic Letters 2.0: A New Beginning

    Erick M. Carreira, Kuiling Ding, Margaret Brimble, Hung-wen Liu, Pauline Chiu, Nuno Maulide, Kavirayani R. Prasad, Zhenfeng Xi, Sarah E. Reisman, Shigehiro Yamaguchi, Tobias Ritter, Jin-Quan Yu

    ORGANIC LETTERS   Vol. 21 ( 1 ) page: 1 - 4   2019.1

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    DOI: 10.1021/acs.orglett.8b03964

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  57. Negative fluorescence anisotropy of phosphole oxide-based dyes in nematic liquid crystals Reviewed

    Takuya Ohzono, Tetsuo Yatabe, Chenguang Wang, Aiko Fukazawa, Shigehiro Yamaguchi

    COMMUNICATIONS CHEMISTRY   Vol. 1   page: 52   2018.9

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    It is important to understand how solute molecules align in anisotropic media such as liquid crystals and biological membranes. Alignment of fluorescent probes used in polarised fluorescence microscopy is of interest because anisotropy of the medium is indirectly estimated through the fluorescence intensity originating from the transition dipole moments fixed on the molecule. Here we report fluorescence anisotropies of a series of phosphole oxide-based dyes with an elongated pi-conjugated system, along which the transition dipole moment lies, in nematic liquid crystals. We observe that as the number, size and rigidity of substituents protruding from the pi-conjugated plane increase, the transition dipole moment tends to tilt away from the nematic director over the magic angle, similar to 54.7 degrees, showing conspicuous negative fluorescence anisotropy. Analysis of molecular shapes suggests that the substitutions modulate the interaction with the nematic mean field, impacting the direction of the principal molecular axis aligned with the nematic director.

    DOI: 10.1038/s42004-018-0055-6

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  58. Phosphorus-containing fluorophores for bio-imaging

    Yamaguchi Shigehiro

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   Vol. 256   2018.8

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  59. End-Capping pi-Conjugated Systems with Medium-Sized Sulfur-Containing Rings: A Route Towards Solution-Processable Air-Stable Semiconductors Reviewed

    Aiko Fukazawa, Yusuke Toda, Masahiro Hayakawa, Anna Sekioka, Hiroyuki Ishii, Toshihiro Okamoto, Jun Takeya, Yuh Hijikata, Shigehiro Yamaguchi

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 24 ( 44 ) page: 11503 - 11510   2018.8

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    The sulfur-containing nine-membered heterocycle thiacyclononene (TN) was evaluated as a new type of end-capping group for pi-conjugated systems. A systematic study on TN-capped -oligothiophenes (TNnTs; n=4-7) revealed that the capping with TN, which adopts a bent conformation, imparts the resulting oligothiophenes with drastically increased solubility at approximately 140 degrees C and high electrochemical stability, whereas the electronic structure remains virtually unperturbed. The even-numbered oligothiophenes TN4T and TN6T form characteristic offset herringbone-type packing structures on account of the steric repulsion between the TN rings and the presence of intermolecular nonbonding S center dot center dot center dot S interactions. This packing mode in combination with the high solubility enabled the solution-process fabrication of field-effect transistors based on TN6T, which exhibited a high performance without degradation even upon exposure to air.

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  60. Donor-pi-Acceptor Type Unsymmetrical Triarylborane-Based Fluorophores: Synthesis, Fluorescence Properties, and Photostability

    Masato Ito, Emi Ito, Masato Hirai, Shigehiro Yamaguchi

    JOURNAL OF ORGANIC CHEMISTRY   Vol. 83 ( 15 ) page: 8449 - 8456   2018.8

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    A two-step synthesis to prepare tricoordinate organoboron compounds bearing three different aryl groups has been developed. After the first aryl substitution to an aryl boronic ester took place, the intermediate species, that is, bis(diarylborinate) species, was isolated as an air- and moisture-stable solid, which allowed the second aryl substitution to carry out in a selective manner. Subsequently, a series of unsymmetrical triarylboranes possessing a sterically bulky aryl group, triarylamine moiety, and para-functionalized phenyl ring was synthesized. Not only did these triarylboranes exhibit remarkable solvent-dependent fluorescence as expected for donor it acceptor (D-pi-A) systems, they were also accompanied by profound persistence against photoirradiation especially for that bearing a 1,3,5-tri-tert-butylphenyl ring. This survey exemplifies that sufficient electronic and steric modification is key to construct photostable D-pi-A type triarylborane-based fluorophores.

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  61. Mechanochromic Luminescent Tetrathiazolylthiophenes: Evaluating the Role of Intermolecular Interactions through Pressure and Temperature-Dependent Raman Spectroscopy

    Mosca S., Milani A., Pena-Alvarez M., Yamaguchi S., Hernandez V., Ruiz Delgado M. C., Castiglioni C.

    JOURNAL OF PHYSICAL CHEMISTRY C   Vol. 122 ( 30 ) page: 17537 - 17543   2018.8

  62. A Highly Photostable Near-Infrared Labeling Agent Based on a Phospha-rhodamine for Long-Term and Deep Imaging Reviewed International journal

    Marek Grzybowski, Masayasu Taki, Kieko Senda, Yoshikatsu Sato, Tetsuro Ariyoshi, Yasushi Okada, Ryosuke Kawakami, Takeshi Imamura, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 57 ( 32 ) page: 10137 - 10141   2018.8

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    Various fluorescence microscopy techniques require bright NIR-emitting fluorophores with high chemical and photostability. Now, the significant performance improvement of phosphorus-substituted rhodamine dyes (PORs) upon substitution at the 9-position with a 2,6-dimethoxyphenyl group is reported. The thus obtained dye PREX 710 was used to stain mitochondria in living cells, which allowed long-term and three-color imaging in the vis-NIR range. Moreover, the high fluorescence longevity of PREX 710 allows tracking a dye-labeled biomolecule by single-molecule microscopy under physiological conditions. Deep imaging of blood vessels in mice brain has also been achieved using the bright NIR-emitting PREX 710-dextran conjugate.

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  63. Electronic Properties of Substitutionally Boron-Doped Graphene Nanoribbons on a Au(111) Surface Reviewed

    Eduard Carbonell-Sanroma, Aran Garcia-Lekue, Martina Corso, Guillaume Vasseur, Pedro Brandimarte, Jorge Lobo-Checa, Dimas G. de Oteyza, Jingcheng Li, Shigeki Kawai, Shohei Saito, Shigehiro Yamaguchi, J. Enrique Ortega, Daniel Sanchez-Portal, Jose Ignacio Pascual

    JOURNAL OF PHYSICAL CHEMISTRY C   Vol. 122 ( 28 ) page: 16092 - 16099   2018.7

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    High-quality graphene nanoribbons (GNRs) grown by on-surface synthesis strategies with atomic precision can be controllably doped by inserting heteroatoms or chemical groups in the molecular precursors. Here, we study the electronic structure of armchair GNRs substitutionally doped with di-boron moieties at the center, through a combination of scanning tunneling spectroscopy, angle resolved photoemission, and density functional theory simulations. Boron atoms appear with a small displacement toward the surface, signaling their stronger interactions with the metal. We find two boron-rich flat bands emerging as impurity states inside the GNR band gap, one of them particularly broadened after its hybridization with the gold surface states. In addition, the boron atoms shift the conduction and valence bands of the pristine GNR away from the gap edge and leave unaffected the bands above and below, which become the new frontier bands and have a negligible boron character. This is due to the selective mixing of boron states with GNR bands according to their symmetry. Our results depict that the GNR band structure can be tuned by modifying the separation between di-boron moieties.

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  64. A planarized B-phenyldibenzoborepin: impact of structural constraint on its electronic properties and Lewis acidity

    Naoki Ando, Tomokatsu Kushida, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 54 ( 41 ) page: 5213 - 5216   2018.5

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    A B-phenyldibenzo[b,f]borepin planarized with two methylene bridges was synthesized. The structural constraint on the B-phenyl group resulted in a bathochromic shift of the absorption and fluorescence properties as well as enhanced Lewis acidity. A donor--acceptor type derivative based on this scaffold exhibited intense fluorescence irrespective of the solvent polarity.

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  65. A far-red emitting fluorescent probe for cytosolic Ca2+ion based on phospha-fluorescein scaffold

    Ogasawara Hiroaki, Taki Masayasu, Sato Yoshikatsu, Yamaguchi Shigehiro

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY   Vol. 255   2018.3

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  66. Near infrared two-photon-excited and -emissive dyes based on a strapped excited-state intramolecular proton-transfer (ESIPT) scaffold Reviewed

    Naoya Suzuki, Kayo Suda, Daisuke Yokogawa, Hirotaka Kitoh-Nishioka, Stephan Irle, Akihiro Ando, Luis M. G. Abegao, Kenji Kamada, Aiko Fukazawa, Shigehiro Yamaguchi

    CHEMICAL SCIENCE   Vol. 9 ( 10 ) page: 2666 - 2673   2018.3

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    Fluorophores that can undergo excited-state intramolecular proton transfer (ESIPT) represent promising scaffolds for the design of compounds that show red-shifted fluorescence. Herein, we disclose new near infrared-emissive materials based on a dialkylamine-strapped 2,5-dithienylpyrrole as an ESIPT scaffold. The introduction of electron-accepting units to the terminal positions of this scaffold generates acceptor-pi-donor-pi-acceptor (A-pi-D-pi-A) type pi-conjugated compounds. Following the ESIPT, the electron-donating ability of the core scaffold increases, which results in a substantially red-shifted emission in the NIR region, while increasing the oscillator strength. The electron-accepting units play a vital role to achieve intense and red-shifted emission from the ESIPT state. The strapped dialkylamine chain that forms an intramolecular hydrogen bond is also essential to induce the ESIPT. Moreover, an extended A-pi-D-pi-A skeleton enables two-photon excitation with the NIR light. One of the derivatives that satisfy these features, i.e., borylethenyl-substituted 5, exhibited an intense NIR emission in polar solvents such as acetone (lambda(em) = 708 nm, phi(F) = 0.55) with a strong two-photon-absorption band in the NIR region.

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  67. Seeded Polymerization through the Interplay of Folding and Aggregation of an Amino-Acid-based Diamide

    Soichiro Ogi, Kentaro Matsumoto, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 57 ( 9 ) page: 2339 - 2343   2018.2

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    Amino acid based diamides are widely used as a substructure in supramolecular polymers and are also key components of polypeptides that help to understand protein folding. The interplay of folding and aggregation of a diamide was used to achieve seed-initiated supramolecular polymerization. For that purpose, a pyrene-substituted diamide was synthesized in which pyrene is used as a tracer to monitor the supramolecular polymerization. Thermodynamics and time-dependent studies revealed that the folding of the diamide moiety, via the formation of intramolecular hydrogen bonds, effectively prevents a spontaneous nucleation that leads to supramolecular polymerization. Under such out-of-equilibrium conditions, the addition of seeds successfully initiates the supramolecular polymerization. These results demonstrate the utility of such amino acid based diamides in programmable supramolecular polymerizations.

    DOI: 10.1002/anie.201712119

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  68. A far-red fluorescent probe based on a phospha-fluorescein scaffold for cytosolic calcium imaging

    Hiroaki Ogasawara, Marek Grzybowski, Riho Hosokawa, Yoshikatsu Sato, Masayasu Taki, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 54 ( 3 ) page: 299 - 302   2018.1

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    The far-red emissive fluorescent probe CaPF-1 based on a phospha-fluorescein scaffold enables the detection of cytosolic calcium ions in living cells. The probe can be excited in the red region (lambda(abs) = 636 nm) and exhibits a sufficiently high fluorescence turn-on response in the far-red region (lambda(em) = 663 nm) upon complexation with calcium ions. The hydrophilic and anionic characteristics of this phospha-fluorescein fluorophore allowed the cytosolic localization of CaPF-1. Moreover, it was possible to visualize histamineinduced calcium oscillation in HeLa cells using CaPF-1.

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  69. Antiaromatic Dithieno-1,2-dihydro-1,2-diborin Splits Diatomic Hydrogen

    Takafumi Araki, Masato Hirai, Atsushi Wakamiya, Warren E. Piers, Shigehiro Yamaguchi

    CHEMISTRY LETTERS   Vol. 46 ( 12 ) page: 1714 - 1717   2017.12

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    B,B-Dimesityl-substituted dithieno-1,2-dihydro-1,2-diborin was synthesized and its properties and reactivity were studied. Owing to the noticeably electron-deficient and antiaromatic character of the 1,2-dihydro-1,2-diborin ring, this compound was found to homolytically cleave diatomic hydrogen (H-2) gas at ambient temperature under 1 atm to afford a hydrogen-bridged bis(borane). This reaction was accompanied by a dramatic color change from dark green to yellow in addition to a turn-on fluorescence response.

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  70. Phosphole P-Oxide-Containing pi-Electron Materials: Synthesis and Applications in Fluorescence Imaging

    Yamaguchi Shigehiro, Fukazawa Aiko, Taki Masayasu

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   Vol. 75 ( 11 ) page: 1179-1187   2017.11

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  71. Structural Monitoring of the Onset of Excited-State Aromaticity in a Liquid Crystal Phase

    Masaki Hada, Shohei Saito, Sei'ichi Tanaka, Ryuma Sato, Masahiko Yoshimura, Kazuhiro Mouri, Kyohei Matsuo, Shigehiro Yamaguchi, Mitsuo Hara, Yasuhiko Hayashi, Fynn Roehricht, Rainer Herges, Yasuteru Shigeta, Ken Onda, R. J. Dwayne Miller

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 139 ( 44 ) page: 15792 - 15800   2017.11

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    Aromaticity of photoexcited molecules is an important concept in organic chemistry. Its theory, Baird's rule for triplet aromaticity since 1972 gives the rationale of photoinduced conformational changes and photochemical reactivities of cyclic pi-conjugated systems. However, it is still challenging to monitor the dynamic structural change induced by the excited-state aromaticity, particularly in condensed materials. Here we report direct structural observation of a molecular motion and a subsequent packing deformation accompanied by the excited-state aromaticity. Photoactive liquid crystal (LC) molecules featuring a pi-expanded cyclooctatetraene core unit are orientationally ordered but loosely packed in a columnar LC phase, and therefore a photoinduced conformational planarization by the excited-state aromaticity has been successfully observed by time-resolved electron diffractometry and vibrational spectroscopy. The structural change took place in the vicinity of excited molecules, producing a twisted stacking structure. A nanoscale torque driven by the excited-state aromaticity can be used as the working mechanism of new photoresponsive materials.

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  72. An Expedient Procedure for the Synthesis of Benzo[4,5]silolo[2,3-b]thiophenes and Related Systems

    Susanne Baehr, Hiroaki Ogasawara, Shigehiro Yamaguchi, Martin Oestreich

    ORGANOMETALLICS   Vol. 36 ( 20 ) page: 4013 - 4019   2017.10

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    The straightforward assembly of various thiophene-fused benzosiloles is accomplished by 2-fold metalation of benzo[b]thiophenes substituted at C3 with ortho-brominated aryl groups followed by electrophilic substitution with dichlorosilanes. The method relies on the innate acidity of the C(sp(2))-H bond at C2 of benzo[b]thiophenes and the halogen-metal exchange of the proximal C(sp(2))-Br bond. The related indole- and benzofuran-annulated systems are also accessible, but these siloles are chemically less stable. An example of a thiophene-fused benzogermole is included as well.

    DOI: 10.1021/acs.organomet.7b00619

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  73. Boron-Stabilized Planar Neutral pi-Radicals with Well-Balanced Ambipolar Charge-Transport Properties

    Tomokatsu Kushida, Shusuke Shirai, Naoki Ando, Toshihiro Okamoto, Hiroyuki Ishi, Hiroyuki Matsui, Masakazu Yamagishi, Takafumi Uemura, Junto Tsurumi, Shun Watanabe, Jun Takeya, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 139 ( 41 ) page: 14336 - 14339   2017.10

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    Organic neutral pi-monoradicals are promising semiconductors with balanced ambipolar carrier transport abilities, which arise from virtually identical spatial distribution of their singly occupied and unoccupied molecular orbitals, SOMO(alpha) and SOMO(beta), respectively. Herein, we disclose a boron-stabilized triphenylmethyl radical that shows outstanding thermal stability and resistance toward atmospheric conditions due to the substantial spin delocalization. The radical is used to fabricate organic Mott-insulator transistors that operate at room temperature, wherein the radical exhibits well-balanced ambipolar carrier transport properties.

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  74. Structural Monitoring of the Onset of Excited-State Aromaticity in a Liquid Crystal Phase Reviewed

    Hada, Masaki, Saito, Shohei, Tanaka, Sei'ichi, Sato, Ryuma, Yoshimura, Masahiko, Mouri, Kazuhiro, Matsuo, Kyohei, Yamaguchi, Shigehiro, Hara, Mitsuo, Hayashi, Yasuhiko, Röhricht, Fynn, Herges, Rainer, Shigeta, Yasuteru, Onda, Ken, Miller, R J Dwayne

    Journal of the American Chemical Society   Vol. 139   page: 15792 - 15800   2017.10

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  75. Photochemical Intramolecular C-H Addition of Dimesityl(hetero)arylboranes through a [1,6]-Sigmatropic Rearrangement

    Naoki Ando, Aiko Fukazawa, Tomokatsu Kushida, Yoshihito Shiota, Shuhei Itoyama, Kazunari Yoshizawa, Yasunori Matsui, Yutaro Kuramoto, Hiroshi Ikeda, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 56 ( 40 ) page: 12210 - 12214   2017.9

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    A new reaction mode for triarylboranes under photochemical conditions was discovered. Photoirradiation of dimesitylboryl-substituted (hetero)arenes produced spirocyclic boraindanes, where one of the C-H bonds in the ortho-methyl groups of the mesityl substituents was formally added in a syn fashion to a C-C double bond of the (hetero)aryl group. Quantum chemical calculations and laser flash photolysis measurements indicated that the reaction proceeds through a [1,6]-sigmatropic rearrangement. This behavior is reminiscent of the photochemical reaction mode of arylalkenylketones, thus demonstrating the isosteric relation between tricoordinate organoboron compounds and the corresponding pseudo-carbocationic species in terms of pericyclic reactions. Despite the disrupted -conjugation, the resulting spirocyclic boraindanes exhibited a characteristic absorption band at relatively long wavelengths (=370400 nm).

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  76. Selective Conversion of P=O-Bridged Rhodamines into P=O-Rhodols: Solvatochromic Near-Infrared Fluorophores

    Marek Grzybowski, Masayasu Taki, Shigehiro Yamaguchi

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 23 ( 53 ) page: 13028 - 13032   2017.9

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    The substitution of an oxygen atom in rhodols with a phosphine oxide (P=O) moiety affords P=O-bridged rhodols as a new type of near-infrared (NIR) fluorophore. This compound class can be readily accessed upon exposure of the corresponding rhodamines to aqueous basic conditions. The electron-withdrawing effect of the P=O group facilitates the hydrolytic deamination, and, moreover, prolonged exposure to aqueous basic conditions generates P=O-bridged fluoresceins, that is, a series of three P=O-bridged xanthene dyes is available in one simple operation. The P=O-bridged rhodols show significant bathochromic shifts of the longest-wavelength absorption maximum (Delta lambda = 125 nm; > 3600 cm(-1)) upon changing the solvent from toluene to water, whereas the emission is shifted less drastically (Delta lambda = 70 nm; 1600 cm @ 1). The hydrogen bonding between the P=O and C=O groups with protic solvents results in substantial stabilization of the LUMO level, which is responsible for the solvatochromism.

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  77. Photochemical Intramolecular C−H Addition of Dimesityl(hetero)arylboranes through a [1,6]-Sigmatropic Rearrangement Reviewed

    Naoki Ando, Aiko Fukazawa, Tomokatsu Kushida, Yoshihito Shiota, Shuhei Itoyama, Kazunari Yoshizawa, Yasunori Matsui, Yutaro Kuramoto, Hiroshi Ikeda, Shigehiro Yamaguchi

    Angewandte Chemie   Vol. 129 ( 40 ) page: 12378   2017.9

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    DOI: 10.1002/ange.201706929

  78. Synthesis of seminaphtho-phospha-fluorescein dyes based on the consecutive arylation of aryldichlorophosphines

    Aiko Fukazawa, Junichi Usuba, Raul A. Adler, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 53 ( 61 ) page: 8565 - 8568   2017.8

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    Seminaphtho-phospha-fluorescein (SNAPF), a phosphine-oxide-containing unsymmetric fluorescein dye, was synthesized based on the consecutive arylation of PhPCl2, followed by Friedel-Crafts cyclization. The resulting SNAPF exhibited several attractive photo-physical properties including an intense fluorescence in the NIR region and a large Stokes shift.

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  79. Super-Photostable Phosphole-Based Dye for Multiple-Acquisition Stimulated Emission Depletion Imaging

    Chenguang Wang, Masayasu Taki, Yoshikatsu Sato, Aiko Fukazawa, Tetsuya Higashiyama, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 139 ( 30 ) page: 10374 - 10381   2017.8

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    As stimulated emission depletion (STED) microscopy can provide structural details of cells with an optical resolution beyond the diffraction limit, it has become an indispensable tool in cell biology. However, the intense STED laser beam usually causes rapid photobleaching of the employed fluorescent dyes, which significantly limits the utility of STED microscopy from a practical perspective. Herein we report a new design of super-photostable dye, PhoxBright 430 (PB430), comprising a fully ring-fused pi-conjugated skeleton with an electron-accepting phosphole pi-oxide unit. We previously developed a super-photostable dye C-Naphox by combining the phosphole unit with an electron-donating triphenylamine moiety. In PB430, removal of the amino group alters the transition type from intramolecular charge transfer character to pi-pi* transition character, which gives rise to intense fluorescence insensitive to molecular environment in terms of fluorescence colors and intensity, and bright fluorescence even in aqueous media. PB430 also furnishes high solubility in water, and is capable of labeling proteins with maintaining high fluorescence quantum yields. This dye exhibits outstanding resistance to photoirradiation even under the STED conditions and allows continuous acquisition of STED images. Indeed, using a PB430-conjugated antibody, we succeed in attaining a 3-D reconstruction of super-resolution STED images as well as photostability-based multicolor STED imaging of fluorescently labeled cytoskeletal structures.

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  80. ESIPT-active organic compounds with white luminescence based on crystallization-induced keto emission (CIKE)

    Huapeng Liu, Xiao Cheng, Houyu Zhang, Yue Wang, Hongyu Zhang, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 53 ( 55 ) page: 7832 - 7835   2017.7

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    Structurally simple pyrazole derivatives that exhibit excited-state intramolecular proton transfer (ESIPT) were synthesized. While these compounds displayed deep violet fluorescence in solution, in the crystalline state they showed white emission from the enol and keto forms.

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  81. Structures and Physical Properties of Chemically Reduced Diindenosiloles and Their pi-Extended Derivatives

    Ryo Takano, Ryo Shintani, Aiko Fukazawa, Shigehiro Yamaguchi, Koji Nakabayashi, Shin-ichi Ohkoshi, Kyoko Nozaki

    ORGANOMETALLICS   Vol. 36 ( 14 ) page: 2646 - 2653   2017.7

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    Diindenosilole Si1, a silicon-bridged fulvalene derivative, was successfully reduced to its dianions using various alkali metals, and the structures were characterized by X-ray crystallographic analysis. Radical anions of Si1 as well as dianions of pi-extended Si3 could also be synthesized, and the structural and physical properties were systematically compared. It was also found that the NMR spectra of dianions Si1(2-) and Si3(2-) show countercation and temperature dependency for their signal broadness, indicating the possible existence of thermal interconversion between closed-shell singlet states and open-shell triplet states.

    DOI: 10.1021/acs.organomet.7b00260

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  82. A Near-Infrared Dye That Undergoes Multiple Interconversions through Acid-Base Equilibrium and Reversible Redox Processes Reviewed

    Kengo Asai, Aiko Fukazawa, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 56 ( 24 ) page: 6848 - 6852   2017.6

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    A near-infrared (NIR) polymethine dye (1), consisting of a cyclohepta[1,2-b; 4,3-b'] dithiophene and two phenol moieties, was synthesized. This dye exhibited pH-responsive changes in its photophysical properties due to a two-step acid-base equilibrium that produced a protonated cation (1H(+)) and an anion (1(-)). While 1H(+) showed an intense fluorescence in the red region of the visible spectrum, 1(-) exhibited a strong absorption in the NIR region. The tropylium ion character in 1H(+) induces high pK(a1) and pK(a2) values for 1. Moreover, a stable radical (1(center dot)) was prepared, which showed a NIR absorption band with a maximum at circa 1600 nm. The cyclic voltammogram of 1(center dot) revealed a two-step reversible redox process that produced 1(-) and the cation 1(+), which is different from 1H(+). These redox processes accompany drastic electrochromic changes in the vis-NIR region. Overall, 1 is susceptible to multiple interconversions between five forms, due to the multifaceted character of the cycloheptadithiophene skeleton.

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  83. Flapping viscosity probe that shows polarity-independent ratiometric fluorescence

    Ryota Kotani, Hikaru Sotome, Hajime Okajima, Soichi Yokoyama, Yumi Nakaike, Akihiro Kashiwagi, Chigusa Mori, Yuki Nakada, Shigehiro Yamaguchi, Atsuhiro Osuka, Akira Sakamoto, Hiroshi Miyasaka, Shohei Saito

    JOURNAL OF MATERIALS CHEMISTRY C   Vol. 5 ( 21 ) page: 5248 - 5256   2017.6

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    A variety of fluorescent molecular viscosity probes have been widely used for mapping the local viscosity in cells and for monitoring the microenvironments in materials. However, their viscosity-sensing structural design still relies strongly on molecular rotors featuring intramolecular rotational dynamics. Here we report flapping molecules (FLAP) as a ratiometric viscosity-sensing fluorophore that shows polarity-independent dual fluorescence. Viscosity-sensing mechanism is based on a unique V-shaped-to-planar conformational change in the singlet excited state (S-1), in which the flexible motion of an eight-membered ring plays an important role. Fast conformational dynamics have been studied by time-resolved spectroscopies, and the viscochromic properties have been quantitatively analyzed. Application of FLAP to monitoring the curing process of epoxy resins has also been demonstrated, in which other typical environment-sensitive dyes did not work as a local viscosity probe.

    DOI: 10.1039/c7tc01533j

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  84. Synthesis and Physical Properties of Strained Doubly Phosphorus-Bridged Biaryls and Viologens

    Tobias W. Greulich, Eriko Yamaguchi, Carsten Doerenkamp, Maximilian Luebbesmeyer, Constantin G. Daniliuc, Aiko Fukazawa, Hellmut Eckert, Shigehiro Yamaguchi, Armido Studer

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 23 ( 25 ) page: 6029 - 6033   2017.5

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    New P/N-containing -electron systems comprising fully planar biaryl arrays are synthesized by multiple radical phosphanylation. The biaryl moiety in these highly strained planar -systems is rigidified by double P-bridging. The electronic properties of the core biaryl entity are varied by introducing N-donor substituents or by installing N-atoms within the -system, thereby moving to the viologen core structure. The electrochemical and photophysical properties of these compounds are discussed and compared with those of related systems.

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  85. Facile Synthesis of Polycyclic Pentalenes with Enhanced Huckel Antiaromaticity

    Hiroya Oshima, Aiko Fukazawa, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 56 ( 12 ) page: 3270 - 3274   2017.3

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    Pentalenes represent highly reactive Huckel antiaromatics with 8 pi electrons. Usually, pentalenes are stabilized by incorporation of two benzene rings in a fused fashion. In dibenzo[a,e]pentalenes, however, the high aromaticity of the fused benzene rings compromises the inherent antiaromaticity of the pentalene core. Herein, we disclose that this forfeited antiaromaticity can be restored by fusing four additional aromatic rings onto the peripheral positions of dibenzo[ a, e]pentalenes. Such polycyclic pentalenes were prepared by successive transannular cyclizations via in situ-generated tetrakisdehydro[16]annulenes. The thus obtained compounds showed intriguing properties, for example, characteristic absorptions in the visible-to-near-infrared (NIR) region and low reduction potentials. These results hence afford a design principle to produce highly antiaromatic yet stable pentalenes. The antiaromaticity of the pentalene core can be widely tuned via the degree of aromaticity of the peripherally fused rings.

    DOI: 10.1002/anie.201611344

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  86. Color-tunable fluorescent nanoparticles encapsulating trialkylsilyl-substituted pyrene liquids

    Masayasu Taki, Saki Azeyanagi, Kenzo Hayashi, Shigehiro Yamaguchi

    JOURNAL OF MATERIALS CHEMISTRY C   Vol. 5 ( 8 ) page: 2142 - 2148   2017.2

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    The development of emissive liquid dyes containing trialkylsilyl groups, and their use in the preparation of fluorescent organic nanoparticles (FONs) are described. A series of trialkylsilyl-substituted pyrenes is synthesized as oils, whose viscosity depends on the nature of the alkyl groups. The neat compounds show intense excimer emission with maxima of around 460-480 nm and quantum yields of 0.5-0.7. The low viscosity (eta = 162 cP) of 2-tri((Z)-3-hexen-1-yl)silylpyrene (1) allows the preparation of spherical nanoparticles (NP1) in the presence of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol. NP1 shows a hydrodynamic diameter of 161 +/- 48 nm and maintains an excimer emission similar to that of neat 1. NP1 in water spontaneously absorbs dopant dyes into its liquid core, and simultaneous doping with two dyes is also possible. When using green-emissive C545T and red-emissive DCJTB dyes as dopants, efficient Forster resonance energy transfer (FRET) occurs from the pyrene excimer to the dyes. Extensive emission color tuning is thus achieved as evident from a plot of the emission colors of doped and undoped NP1 on the CIE 1931 xy chromaticity diagram. These results demonstrate the efficacy of the present design strategy for color-tunable FONs that do not require premixing of dopant dyes.

    DOI: 10.1039/c6tc05208h

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  87. Color-tunable fluorescent nanoparticles encapsulating trialkylsilyl-substituted pyrene liquids

    Masayasu Taki, Saki Azeyanagi, Kenzo Hayashi, Shigehiro Yamaguchi, Shigehiro Yamaguchi

    Journal of Materials Chemistry C   Vol. 5   page: 2142 - 2148   2017.1

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    © The Royal Society of Chemistry. The development of emissive liquid dyes containing trialkylsilyl groups, and their use in the preparation of fluorescent organic nanoparticles (FONs) are described. A series of trialkylsilyl-substituted pyrenes is synthesized as oils, whose viscosity depends on the nature of the alkyl groups. The neat compounds show intense excimer emission with maxima of around 460-480 nm and quantum yields of 0.5-0.7. The low viscosity (η = 162 cP) of 2-tri((Z)-3-hexen-1-yl)silylpyrene (1) allows the preparation of spherical nanoparticles (NP1) in the presence of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol. NP1 shows a hydrodynamic diameter of 161 ± 48 nm and maintains an excimer emission similar to that of neat 1. NP1 in water spontaneously absorbs dopant dyes into its liquid core, and simultaneous doping with two dyes is also possible. When using green-emissive C545T and red-emissive DCJTB dyes as dopants, efficient Förster resonance energy transfer (FRET) occurs from the pyrene excimer to the dyes. Extensive emission color tuning is thus achieved as evident from a plot of the emission colors of doped and undoped NP1 on the CIE 1931 xy chromaticity diagram. These results demonstrate the efficacy of the present design strategy for color-tunable FONs that do not require premixing of dopant dyes.

    DOI: 10.1039/c6tc05208h

    Scopus

  88. Quantum Dots Embedded in Graphene Nanoribbons by Chemical Substitution Reviewed

    Eduard Carbonell-Sanroma, Pedro Brandimarte, Richard Balog, Martina Corso, Shigeki Kawai, Aran Garcia-Lekue, Shohei Saito, Shigehiro Yamaguchi, Ernst Meyer, Daniel Sanchez-Portal, Jose Ignacio Pascual

    NANO LETTERS   Vol. 17 ( 1 ) page: 50 - 56   2017.1

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    Bottom-up chemical reactions of selected molecular precursors on a gold surface can produce high quality graphene nanoribbons (GNRs). Here, we report on the formation of quantum dots embedded in an armchair GNR by substitutional inclusion of pairs of boron atoms into the GNR backbone. The boron inclusion is achieved through the addition of a small amount of boron substituted precursors during the formation of pristine GNRs. In the pristine region between two boron pairs, the nanoribbons show a discretization of their valence band into confined modes compatible with a Fabry-Perot resonator. Transport simulations of the scattering properties of the boron pairs reveal that they selectively confine the first valence band of the pristine ribbon while allowing an efficient electron transmission of the second one. Such band-dependent electron scattering stems from the symmetry matching between the electronic wave functions of the states from the pristine nanoribbons and those localized at the boron pairs.

    DOI: 10.1021/acs.nanolett.6b03148

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  89. Steric Shielding vs Structural Constraint in a Boron-Containing Polycyclic Aromatic Hydrocarbon Reviewed

    V. M. Hertz, N. Ando, M. Hirai, M. Bolte, H.-W. Lerner, S. Yamaguchi, M. Wagner

    Organometallics     2016.12

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    DOI: 10.1021/acs.organomet.6b00800

  90. Stable Red-Emissive Cationic Dithienotropylium Dyes Reviewed

    Kengo Asai, Aiko Fukazawa, Shigehiro Yamaguchi

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 22 ( 49 ) page: 17571 - 17575   2016.12

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    A series of thiophene-fused tropylium ions, containing various electron-donating amino groups at the terminal positions, was synthesized. The fusion of the thiophene rings, as well as the presence of the terminal amino groups endows the cationic tropylium ion with excellent stability and high pK(R)(+) values. X-ray crystallographic analysis of these compounds revealed a pronounced quinoidal character for the amino-substituted dithienotropylium skeletons. These compounds exhibit attractive photophysical properties such as strong absorption in the visible region combined with red fluorescence. Theoretical calculations suggested that the 3,3'-bithiophene substructure should be crucial for attaining these photophysical properties.

    DOI: 10.1002/chem.201604509

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  91. A Soluble Dynamic Complex Strategy for the Solution-Processed Fabrication of Organic Thin-Film Transistors of a Boron-Containing Polycyclic Aromatic Hydrocarbon Reviewed

    K. Matsuo, S. Saito, S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 55 ( 39 ) page: 11984 - 11988   2016.9

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    DOI: 10.1002/anie.201605221

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  92. Light-melt adhesive based on dynamic carbon frameworks in a columnar liquid-crystal phase Reviewed

    Shohei Saito, Shunpei Nobusue, Eri Tsuzaka, Chunxue Yuan, Chigusa Mori, Mitsuo Hara, Takahiro Seki, Cristopher Camacho, Stephan Irle, Shigehiro Yamaguchi

    NATURE COMMUNICATIONS   Vol. 7   page: 12094   2016.7

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    Liquid crystal (LC) provides a suitable platform to exploit structural motions of molecules in a condensed phase. Amplification of the structural changes enables a variety of technologies not only in LC displays but also in other applications. Until very recently, however, a practical use of LCs for removable adhesives has not been explored, although a spontaneous disorganization of LC materials can be easily triggered by light-induced isomerization of photoactive components. The difficulty of such application derives from the requirements for simultaneous implementation of sufficient bonding strength and its rapid disappearance by photoirradiation. Here we report a dynamic molecular LC material that meets these requirements. Columnar-stacked V-shaped carbon frameworks display sufficient bonding strength even during heating conditions, while its bonding ability is immediately lost by a light-induced self-melting function. The light-melt adhesive is reusable and its fluorescence colour reversibly changes during the cycle, visualizing the bonding/nonbonding phases of the adhesive.

    DOI: 10.1038/ncomms12094

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  93. A Macrocyclic Fluorophore Dimer with Flexible Linkers: Bright Excimer Emission with a Long Fluorescence Lifetime Reviewed

    Hiroshi Osaki, Chih-Ming Chou, Masayasu Taki, Kai Welke, Daisuke Yokogawa, Stephan Irle, Yoshikatsu Sato, Tetsuya Higashiyama, Shohei Saito, Aiko Fukazawa, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 55 ( 25 ) page: 7131 - 7135   2016.6

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    Bright fluorescent molecules with long fluorescence lifetimes are important for the development of lifetime-based fluorescence imaging techniques. Herein, a molecular design is described for simultaneously attaining long fluorescence lifetime (tau) and high brightness (Phi(F) x epsilon) in a system that features macrocyclic dimerization of fluorescent p-conjugated skeletons with flexible linkers. An alkylene-linked macrocyclic dimer of bis(thienylethynyl)anthracene was found to show excimer emission with a long fluorescence lifetime (tau approximate to 19 ns) in solution, while maintaining high brightness. A comparison with various relevant derivatives revealed that the macrocyclic structure and the length of the alkylene chains play crucial roles in attaining these properties. In vitro time-gated imaging experiments were conducted as a proof-of-principle for the superiority of this macrocyclic fluorophore relative to the commercial fluorescent dye Alexa Fluor 488.

    DOI: 10.1002/anie.201602239

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  94. Pyridyl Directed Catalyst-Free trans-Hydroboration of Internal Alkynes Reviewed

    Kang Yuan, Naoya Suzuki, Soren K. Mellerup, Xiang Wang, Shigehiro Yamaguchi, Suning Wang

    ORGANIC LETTERS   Vol. 18 ( 4 ) page: 720 - 723   2016.2

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    We report the first examples of straightforward trans-hydroboration of internal alkynes at room temperature with 9-BBN, producing five-membered BN-heterocycles. Contrary to conventional cis-hydroboration, we demonstrate that the introduction of a pyridyl group switches the stereoselectivity of the reaction. A hydride migration mechanism has been proposed and supported by DFT calculations for the trans-hydroboration. This new hydroboration approach allows facile construction of new blue fluorescent BN-heterocyclic compounds.

    DOI: 10.1021/acs.orglett.5b03698

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  95. A biphenyl containing two electron-donating and two electron-accepting moieties: a rigid and small donor-acceptor-donor ladder system Reviewed

    Tobias W. Greulich, Naoya Suzuki, Constantin G. Daniliuc, Aiko Fukazawa, Eriko Yamaguchi, Armido Studer, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 52 ( 11 ) page: 2374 - 2377   2016

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    Ladder pi-conjugated materials and also push-pull systems belong to important classes of compounds for the development of organic electronic devices. In this communication, a novel pi-conjugated material that unifies the properties of both of these classes is presented. The material comprises a rigid biphenyl framework, which bears two bridging electron-accepting phosphine oxide moieties as well as two electron-donating amino groups. The structure and photophysical properties of this compound are discussed and compared with those of a related system lacking the second P-moiety.

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  96. A planarized 9-phenylanthracene: a simple electron-donating building block for fluorescent materials Reviewed

    Hideaki Iwahara, Tomokatsu Kushida, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 52 ( 6 ) page: 1124 - 1127   2016

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    A 9-phenylanthracene, constrained in a coplanar fashion by two methylene tethers, was synthesized and its optoelectronic properties were investigated. The rigid planarization increased its electron-donating character and induced a bathochromic shift of its absorption, as well as an increased molar absorption coefficient and intense fluorescence. These properties render this compound a promising building block for fluorescent materials.

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  97. Phospha-fluorescein: a red-emissive fluorescein analogue with high photobleaching resistance Reviewed

    Aiko Fukazawa, Shinji Suda, Masayasu Taki, Eriko Yamaguchi, Marek Grzybowski, Yoshikatsu Sato, Tetsuya Higashiyama, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 52 ( 6 ) page: 1120 - 1123   2016

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    Phospha-fluorescein (POF), a phosphine oxide-containing analogue of fluorescein, was synthesized and its photophysical properties were examined. Compared with fluorescein and sila-fluorescein, POF displayed significantly red-shifted absorption and fluorescence as well as superior photobleaching resistance, while retaining the pH-responsive characteristics of fluorescein dyes.

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  98. Boron-doped nanographene: Lewis acidity, redox properties, and battery electrode performance Reviewed

    Shinichiro Osumi, Shohei Saito, Chuandong Dou, Kyohei Matsuo, Keita Kume, Hirofumi Yoshikawa, Kunio Awagaa, Shigehiro Yamaguchi

    CHEMICAL SCIENCE   Vol. 7 ( 1 ) page: 219 - 227   2016

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    The preparation of boron-doped nanocarbon scaffolds with well-defined structures is important for the understanding of the impact of boron doping on their properties and behavior at the molecular level. We recently succeeded in the synthesis of a structurally well-defined nanographene molecule, bearing two boron atoms at the central positions. In this study, the characteristic properties and functions of this boron-doped nanographene were investigated in terms of (1) Lewis acidity, (2) redox properties, and (3) electrode performance in a battery. This boron-doped nanographene was susceptible to chemical adsorption with various Lewis bases, resulting in significant changes in the absorption and fluorescence properties, as well as in the conformation of the honeycomb framework. The two-electron reduction of this boron-doped nanographene produced a dianionic species that showed a substantial biradical character with a triplet ground state. A Li battery electrode, composed of a boron-doped nanographene with small peripheral substituents, displayed a stable performance in the 1.5-4.0 V range with a first discharge capacity of 160 mA h g(-1). These results provide important insights into the effect of boron doping on nanocarbon compounds.

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  99. A Phosphole Oxide Based Fluorescent Dye with Exceptional Resistance to Photobleaching: A Practical Tool for Continuous Imaging in STED Microscopy Reviewed

    Chenguang Wang, Aiko Fukazawa, Masayasu Taki, Yoshikatsu Sato, Tetsuya Higashiyama, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 54 ( 50 ) page: 15213 - 15217   2015.12

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    The development of stimulated emission depletion (STED) microscopy represented a major breakthrough in cellular and molecular biology. However, the intense laser beams required for both excitation and STED usually provoke rapid photobleaching of fluorescent molecular probes, which significantly limits the performance and practical utility of STED microscopy. We herein developed a photoresistant fluorescent dye C-Naphox as a practical tool for STED imaging. With excitation using either a lambda = 405 or 488 nm laser in protic solvents, C-Naphox exhibited an intense red/orange fluorescence (quantum yield phi(F) > 0.7) with a large Stokes shift (circa 5900 cm(-1)). Even after irradiation with a Xe lamp (300 W, lambda(ex) = 460 nm, full width at half maximum (FWHM) = 11 nm) for 12 hours, 99.5 % of C-Naphox remained intact. The high photoresistance of C-Naphox allowed repeated STED imaging of HeLa cells. Even after recording 50 STED images, 83 % of the initial fluorescence intensity persisted.

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  100. A Benzophosphole P-Oxide with an Electron-Donating Group at 3-Position: Enhanced Fluorescence in Polar Solvents Reviewed

    Eriko Yamaguchi, Aiko Fukazawa, Youhei Kosaka, Daisuke Yokogawa, Stephan Irle, Shigehiro Yamaguchi

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   Vol. 88 ( 11 ) page: 1545 - 1552   2015.11

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    Fluorophores with intramolecular charge-transfer (ICT) character in the excited state exhibit significant solvatochromism of their fluorescence. Here, we report an example for such compounds, a benzophosphole P-oxide bearing an electron-donating p-(diphenylamino)phenyl group at the 3-position. While this compound shows only subtle dependence of the absorption maximum on the solvent polarity (lambda(max) = 383-392 nm), its emission maximum is significantly red-shifted upon increasing the solvent polarity (cyclohexane: lambda(em) = 457 nm; DNIF: lambda(em) = 598 nm). Most notably, the fluorescence quantum yields gradually increase with increased Stokes shifts, ultimately reaching Phi(F) = 0.28 in DMF. This trend is fundamentally different from that observed for the corresponding 2-(diphenylamino)phenyl-substituted benzophosphole congener, for which applications as a fluorescent bioimaging probe were previously demonstrated. In this study, the origins of this striking difference are examined by a combined experimental and theoretical approach. Our results suggest that the observed difference arises from a significant contribution of quinoidal resonance forms in the ICT excited state, which suppresses nonradiative decay and hence increases the quantum yield in polar solvents.

    DOI: 10.1246/bcsj.20150238

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  101. A Phosphole Oxide Based Fluorescent Dye with Exceptional Resistance to Photobleaching: A Practical Tool for Continuous Imaging in STED Microscopy Reviewed

    C. Wang, A. Fukazawa, M. Taki, Yoshikatsu Sato, T. Higashiyama, S. Yamaguchi

    Angew. Chem. Int. Ed.     2015.10

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    DOI: DOI: 10.1002/anie.201507939

  102. Designs of Functional pi-Electron Materials based on the Characteristic Features of Boron Reviewed

    Atsushi Wakamiya, Shigehiro Yamaguchi

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   Vol. 88 ( 10 ) page: 1357 - 1377   2015.10

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    Boron, a group 13 element, has several characteristic structural and electronic features: 1) trivalent boron compounds usually adopt a trigonal planar geometry; 2) due to the presence of a vacant p-orbital, effective orbital interaction with pi-conjugated compounds is possible; 3) the presence of a vacant p-orbital is furthermore responsible for high Lewis acidity; 4) the boryl group acts as a pi-electron-accepting group particularly in the excited state. The consequent exploitation of these characteristic features of boron in the molecular design enables us to produce sophisticated pi-functional materials with attractive photophysical and electronic properties. This account article illustrates our systematic studies on the molecular design and the development of functional pi-electron materials using boron as a key element.

    DOI: 10.1246/bcsj.20150151

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  103. Boron-Doped Nanographene: Lewis Acidity, Redox Properties, and Battery Electrode Performance Reviewed

    S. Osumi, S. Saito, C. Dou, K. Matsuo, K. Kume, H. Yoshikawa, K. Awaga, S. Yamaguchi

    Chem. Sci.     2015.9

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    DOI: DOI: 10.1039/c5sc02246k

  104. Atomically-Controlled Substitutional Boron-Doping of Graphene Nanoribbons Reviewed

    S. Kawai, S. Saito, S. Osumi, S. Yamaguchi, A. S. Foster, P. Spijker, E. Meyer

    Nat. Commun.     2015.8

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    DOI: DOI: 10.1038/ncomms9098

  105. Benzophosphole P-Oxide with an Electron-Donating Group at 3-Position: Enhanced Fluorescence in Polar Solvents Reviewed

    E. Yamaguchi, A. Fukazawa, Y. Kosaka, D. Yokogawa, S. Irle, S. Yamaguchi

        2015.8

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    DOI: DOI: 10.1246/bcsj.20150238

  106. Atomically controlled substitutional boron-doping of graphene nanoribbons Reviewed

    Shigeki Kawai, Shohei Saito, Shinichiro Osumi, Shigehiro Yamaguchi, Adam S. Foster, Peter Spijker, Ernst Meyer

    NATURE COMMUNICATIONS   Vol. 6   page: 8098   2015.8

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    Boron is a unique element in terms of electron deficiency and Lewis acidity. Incorporation of boron atoms into an aromatic carbon framework offers a wide variety of functionality. However, the intrinsic instability of organoboron compounds against moisture and oxygen has delayed the development. Here, we present boron-doped graphene nanoribbons (B-GNRs) of widths of N = 7, 14 and 21 by on-surface chemical reactions with an employed organoboron precursor. The location of the boron dopant is well defined in the centre of the B-GNR, corresponding to 4.8 atom%, as programmed. The chemical reactivity of B-GNRs is probed by the adsorption of nitric oxide (NO), which is most effectively trapped by the boron sites, demonstrating the Lewis acid character. Structural properties and the chemical nature of the NO-reacted B-GNR are determined by a combination of scanning tunnelling microscopy, high-resolution atomic force microscopy with a CO tip, and density functional and classical computations.

    DOI: 10.1038/ncomms9098

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  107. A Nonaromatic Thiophene-Fused Heptalene and Its Aromatic Dianion Reviewed

    Hiroya Oshima, Aiko Fukazawa, Takahiro Sasamori, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 54 ( 26 ) page: 7636 - 7639   2015.6

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    Heptalene, a nonaromatic, bicyclic 12 -electron system with a twisted structure, is of great interest with regard to its potential Huckel aromaticity in the two-electron oxidized or reduced forms. The synthesis of thiophene-fused heptalene 5 from the reductive transannular cyclization of bisdehydro[12]annulene 4, and its solid-state structure, which was confirmed by X-ray crystallographic analysis, is presented. Chemical reduction of 5 readily generated the corresponding dianion, which was successfully isolated as [(K[2.2.2]cryptand)(+)](2)5(2-). The X-ray crystallographic analysis of the dianion revealed a shallower saddle structure for the heptalene moiety and a lesser degree of bond alternation relative to 5. (HNMR)-H-1 spectroscopy exposed the effect of a diamagnetic ring current on dianion 5(2-), which was corroborated by nucleus-independent chemical shift (NICS) calculations. These results demonstrate that the heptalene dianion, containing 14 -electrons, does indeed exhibit pronounced degrees of Huckel aromaticity.

    DOI: 10.1002/anie.201501790

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  108. A Red-emitting Ratiometric Fluorescent Probe Based on a Benzophosphole P-Oxide Scaffold for the Detection of Intracellular Sodium Ions Reviewed

    M. Taki, H. Ogasawara, H. Osaki, A. Fukazawa, Y. Sato, K. Ogasawara, T. Higashiyama, S. Yamaguchi

    Chem. Commun.   Vol. 51   page: 11880-11883   2015.6

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    DOI: DOI: 10.1039/C5CC03547C

  109. A Planarized Triphenylborane Mesogen: Discotic Liquid Crystals with Ambipolar Charge-Carrier Transport Properties Reviewed

    Tomokatsu Kushida, Ayumi Shuto, Masafumi Yoshio, Takashi Kato, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 54 ( 23 ) page: 6922 - 6925   2015.6

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    A discotic liquid-crystalline (LC) material, consisting of a planarized triphenylborane mesogen, was synthesized. X-ray diffraction analysis confirmed that this compound forms a hexagonal columnar LC phase with an interfacial distance of 3.57 angstrom between the discs. At ambient temperature, this boron-centered discotic liquid crystal exhibited ambipolar carrier transport properties with electron and hole mobility values of approximately 10(-3) and 3x10(-5)cm(2)V(-1)s(-1), respectively.

    DOI: 10.1002/anie.201502678

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  110. A Nonaromatic Thiophene-fused Heptalene and Its Aromatic Dianion Reviewed

    H. Oshima, A. Fukazawa, T. Sasamori, S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 54   page: 636-7639   2015.5

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    DOI: DOI: 10.1002/anie.201501790

  111. A Cyclic Octithiophene Containing β,β'-Linkages Reviewed

    K. Asai, A. Fukazawa, S. Yamaguchi

    Chem. Commun.   Vol. 51   page: 6096-6099   2015.5

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  112. A Planarized Triphenylborane Mesogen: Discotic Liquid Crystals with Ambipolar Charge-Carrier Transport Properties Reviewed

    T. Kushida, A. Shuto, M. Yoshio, T. Kato, S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 54   page: 6922-6925   2015.4

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    DOI: DOI: 10.1002/anie.201502678

  113. Environment-Sensitive Fluorescent Probe: A Benzophosphole Oxide with an Electron-Donating Substituent Reviewed

    Eriko Yamaguchi, Chenguang Wang, Aiko Fukazawa, Masayasu Taki, Yoshikatsu Sato, Taeko Sasaki, Minako Ueda, Narie Sasaki, Tetsuya Higashiyama, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 54 ( 15 ) page: 4539 - 4543   2015.4

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    Electron-donating aryl groups were attached to electron-accepting benzophosphole skeletons. Among several derivatives thus prepared, one benzophosphole oxide was particularly interesting, as it retained high fluorescence quantum yields even in polar and protic solvents. This phosphole-based compound exhibited a drastic color change of its fluorescence spectrum as a function of the solvent polarity, while the absorption spectra remained virtually unchanged. Capitalizing on these features, this phosphole-based compound was used to stain adipocytes, in which the polarity of subcellular compartments could then be discriminated on the basis of the color change of the fluorescence emission.

    DOI: 10.1002/anie.201500229

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  114. Environment-Sensitive Fluorescent Probe: A Benzophosphole Oxide with an Electron-Donating Substituent Reviewed

    E. Yamaguchi, C. Wang, A. Fukazawa, M. Taki, Y. Sato, T. Sasaki, M. Ueda, N. Sasaki, T. Higashiyama, S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 54   page: 4539-4543   2015.3

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    DOI: DOI: 10.1002/anie.201500229

  115. Highly Bent Crystals Formed by Restrained π-Stacked Columns Connected via Alkylene Linkers with Variable Conformations Reviewed

    Highly Bent Crystals Formed by Restrained π-Stacked Columns Connected via Alkylene Linkers with Variable Conformations

    Chem. Sci.   Vol. 6   page: 2354-2359   2015.2

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    DOI: DOI: 10.1039/C4SC03849E

  116. Fluorescent benzene-centered mono-, bis- and tris-triazapentadiene-boron complexes Reviewed

    Christoph Glotzbach, Nadine Goedeke, Roland Froehlich, Constantin-Gabriel Daniliuc, Shohei Saito, Shigehiro Yamaguchi, Ernst-Ulrich Wuerthwein

    DALTON TRANSACTIONS   Vol. 44 ( 20 ) page: 9659 - 9671   2015

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    A series of novel benzene centered mono-, bis- and tris-1,3,5-triazapentadiene ligands 6a-e was synthesized and investigated with respect to their reactivity towards triphenylborane. The resulting blue-fluorescent boron complexes 14a-e with a six-membered ring chelate structure show excellent thermal and chemical stability. All title compounds were completely characterized including X-ray diffraction studies for 14a-c and 14e. Whereas the absorption spectra of all three classes of compounds are similar, the fluorescence spectra show distinct differences. Thus, the emission spectra of 14a, b show Stokes shifts of 4100-6700 cm(-1) with low quantum yields both in solution and in the solid state. However, the more bulky compounds 14c-e show markedly larger molar extinction coefficients and smaller bathochromic shifts compared to 14a,b. For all compounds, we observe significantly more intense red-shifted fluorescence in the solid state compared to that in dichloromethane solutions. For the interpretation of the absorption properties TD-DFT studies were performed based on DFT geometry optimizations.

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    Other Link: http://orcid.org/0000-0003-1863-9956

  117. A cyclic octithiophene containing beta,beta '-linkages Reviewed

    Kengo Asai, Aiko Fukazawa, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 51 ( 28 ) page: 6096 - 6099   2015

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    A cyclic octithiophene containing two beta,beta '-linkages was synthesized. Due to the large structural change in the excited state, this compound exhibited bathochromically shifted fluorescence. It also showed a small difference between the first and second oxidation potentials, indicative of spin delocalization through the beta,beta '-linkage in the one electron-oxidized state.

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  118. A red-emitting ratiometric fluorescent probe based on a benzophosphole P-oxide scaffold for the detection of intracellular sodium ions Reviewed

    Masayasu Taki, Hiroaki Ogasawara, Hiroshi Osaki, Aiko Fukazawa, Yoshikatsu Sato, Kimi Ogasawara, Tetsuya Higashiyama, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 51 ( 59 ) page: 11880 - 11883   2015

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    We disclose the development of a ratiometric fluorescent probe based on a benzophosphole P-oxide and its application for the detection of intracellular Na+ ions. Excitation by visible light induced red emission from this probe in water, which was subjected to a hypsochromic shift upon complexation with Na+. Based on this change, a ratiometric analysis enabled us to visualise changes in the Na+ concentration in living mammalian cells.

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  119. Highly bent crystals formed by restrained pi-stacked columns connected via alkylene linkers with variable conformations Reviewed

    Chih-Ming Chou, Shunpei Nobusue, Shohei Saito, Daishi Inoue, Daisuke Hashizume, Shigehiro Yamaguchi

    CHEMICAL SCIENCE   Vol. 6 ( 4 ) page: 2354 - 2359   2015

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    A reproducible formation of strongly bent crystals was accomplished by structurally restraining macrocyclic pi-conjugated molecules. The model pi-units consist of two 9,10-bis(2-thienylethynyl)anthracenes with a strong propensity for stacking, which are connected in a macrocyclic fashion via two alkylene linkers. The correlation between the crystalline morphology and the macrocyclic structures restrained by a variety of flexible alkylene linker combinations was systematically studied. Bent crystals were obtained only with specific alkylene linkers of appropriate chain length. The alkylene linkers can adopt different conformations in the crystal packing, so as to fill voids within the macrocycle. The ability to form several similar molecular structures with different alkylene conformations gives rise to contaminations of different crystalline phases within a single crystal, and it is these phase contaminations which are responsible for the bending of the crystals.

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  120. Photodissociation of B-N Lewis Adducts: A Partially Fused Trinaphthylborane with Dual Fluorescence Reviewed

    Kyohei Matsuo, Shohei Saito, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 136 ( 36 ) page: 12580 - 12583   2014.9

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    The synthesis of a planarized trinaphthylborane with partially fused structure is presented. This compound shows not only high chemical and thermal stability but also sufficient Lewis acidity to form Lewis adducts with pyridine derivatives in solution. The BN Lewis adducts exhibit unprecedented photodissociation behavior in the excited state, reminiscent of the photogeneration of carbenium ions from triarylmethane leuco dyes. Consequently, these BN Lewis adducts exhibit dual fluorescence emission arising from the initial tetracoordinate BN adducts and the photodissociated tricoordinate boranes.

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  121. Dearomatization-Induced Transannular Cyclization: Synthesis of Electron-Accepting Thiophene-S,S-Dioxide-Fused Biphenylene Reviewed

    Aiko Fukazawa, Hiroya Oshima, Soji Shimizu, Nagao Kobayashi, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 136 ( 24 ) page: 8738 - 8745   2014.6

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    The transannular cyclization of dehydroannulenes bearing several alkyne moieties in close proximity is a powerful synthetic method for producing polyc-yclic aromatic hydrocarbons. We report that the reactivity can be switched by the aromaticity of the ring skeletons fused with the dehydroannulene core. Thus, while thiophene-fused bisdehydro[12]annulene 1 was handled as a stable compound in the air at room temperature, the oxidation with m-chloroperbenzoic acid from the aromatic thiophene rings to the nonaromatic thiophene-S,S-dioxides induced the transannular cyclization, even at room temperature, which was completed within 1 day to produce the formal [2 + 2] cycloadduct 3. This is in stark contrast to the fact that the thermal cyclization of 1 itself required heating at 80 C for 9 days for completion. Experimental and theoretical studies indicate that the oxidation of even one thiophene ring in 1 sufficiently decreases the activation barrier for the transannular cyclization that proceeds through the 8 pi and 4 pi electrocyclic reaction sequence. The thiophene-S,S-dioxide-fused biphenylene 3 thus produced exhibits a set of intriguing properties, such as a higher electron affinity (E-1/2 = -1.17 V vs Fc and Fc(+)) and a stronger fluorescence (Phi(F) = 0.20) than the other relevant biphenylene derivatives, which have electron-donating and nonfluorescent characteristics.

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  122. A Strap Strategy for Construction of an Excited-State Intramolecular Proton Transfer (ESIPT) System with Dual Fluorescence Reviewed

    N. Suzuki, A. Fukazawa, K. Nagura, S. Saito, H. Kitoh-Nishioka, D. Yokogawa, S. Irle, S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 53   page: 8231-8235   2014.6

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  123. A Strap Strategy for Construction of an Excited-State Intramolecular Proton Transfer (ESIPT) System with Dual Fluorescence Reviewed

    N. Suzuki, A. Fukazawa, K. Nagura, S. Saito, H. Kitoh-Nishioka, D. Yokogawa, S. Irle, S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 53   page: 8231-8235   2014.6

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  124. Dearomatization-Induced Transannular Cyliczation: Synthesis of Electron-Accepting Thiophene-S,S-Dioxide-Fused Biphenylene Reviewed

    A. Fukazawa, H. Oshima, S. Shimizu, N. Kobayashi, and S. Yamaguchi

    J. Am. Chem. Soc.   Vol. 136   page: 8738-8745   2014.6

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    DOI: DOI: 10.1021/ja503499n

  125. Heterotriangulenes pi-Expanded at Bridging Positions Reviewed

    Chih-Ming Chou, Shohei Saito, Shigehiro Yamaguchi

    ORGANIC LETTERS   Vol. 16 ( 11 ) page: 2868 - 2871   2014.6

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    A series of nitrogen-containing heterotriangulenes expanded at the bridging positions has been synthesized. Among them, a dibenzo[c,g]fluorenylidene-substituted derivative has a highly twisted conformation for the overcrowded alkene moieties, which impart a highly electron-accepting character to the electron-donating heterotriangulene skeleton and thereby an NIR absorption as well as multiredox properties with a low reduction potential.

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  126. The B(C6F5)(3) Boron Lewis Acid Route to Arene-Annulated Pentalenes Reviewed

    Chao Chen, Marcel Harhausen, Aiko Fukazawa, Shigehiro Yamaguchi, Roland Froehlich, Constantin G. Daniliuc, Jeffrey L. Petersen, Gerald Kehr, Gerhard Erker

    CHEMISTRY-AN ASIAN JOURNAL   Vol. 9 ( 6 ) page: 1671 - 1681   2014.6

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    4,5-Dimethyl-1,2-bis(1-naphthylethynyl)benzene (12) undergoes a rapid multiple ring-closure reaction upon treatment with the strong boron Lewis acid B(C6F5)(3) to yield the multiply annulated, planar conjugated -system 13 (50% yield). In the course of this reaction, a C6F5 group was transferred from boron to carbon. Treatment of 12 with CH3B(C6F5)(2) proceeded similarly, giving a mixture of 13 (C6F5-transfer) and the product 15, which was formed by CH3-group transfer. 1,2-Bis(phenylethynyl)benzene (8a) reacts similarly with CH3B(C6F5)(2) to yield a mixture of the respective C6F5- and CH3-substituted dibenzopentalenes 10a and 16. The reaction is thought to proceed through zwitterionic intermediates that exhibit vinyl cation reactivities. Some B(C6F5)(3)-substituted species (26, 27) consequently formed by in situ deprotonation upon treatment of the respective 1,2-bis(alkynyl)benzene starting materials (24, 8) with the frustrated Lewis pair B(C6F5)(3)/P(o-tolyl)(3). The overall formation of the C6F5-substituted products formally require HB(C6F5)(2) cleavage in an intermediate dehydroboration step. This was confirmed in the reaction of a thienylethynyl-containing starting material 21 with B(C6F5)(3), which gave the respective annulated pentalene product 23 that had the HB(C6F5)(2) moiety 1,4-added to its thiophene ring. Compounds12-14, 23, and 26 were characterized by X-ray diffraction.

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  127. Heterotriangulenes π-Expanded at Bridging Positions Reviewed

    C. -M. Chou, S. Saito, S. Yamaguchi

    Org. Lett.   Vol. 16   page: 2868-2871   2014.5

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    DOI: DOI: 10.1021/ol501004g

  128. Synthesis of Pyridine N-Oxide-BF2CF3 Complexes and Their Fluorescence Properties Reviewed

    Tomoaki Nishida, Aiko Fukazawa, Eriko Yamaguchi, Hiroya Oshima, Shigehiro Yamaguchi, Motomu Kanai, Yoichiro Kuninobu

    CHEMISTRY-AN ASIAN JOURNAL   Vol. 9 ( 4 ) page: 1026 - 1030   2014.4

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    Pyridine N-oxide-BF2CF3 and -BF2C2F5 complexes and their derivatives were synthesized. Most of the complexes show fluorescence both in solution and in the solid state. By expanding the -conjugated skeleton, the color of the fluorescence could be changed dramatically. A fluorophore with a high solvent dependency could also be produced. Since such compounds can be synthesized on a gram scale in high yield, and are stable to oxygen, water, and heat, the complexes hold great potential as organic functional materials.

    DOI: 10.1002/asia.201301688

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  129. Hybridization of a Flexible Cyclooctatetraene Core and Rigid Aceneimide Wings for Multiluminescent Flapping pi Systems Reviewed

    Chunxue Yuan, Shohei Saito, Cristopher Camacho, Tim Kowalczyk, Stephan Irle, Shigehiro Yamaguchi

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 20 ( 8 ) page: 2193 - 2200   2014.2

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    The hybridization of flexible and rigid -conjugated frameworks is a potent concept for producing new functional materials. In this article, a series of multifluorescent flapping systems that combine a flexible cyclooctatetraene (COT) core and rigid aceneimide wings with various -conjugation lengths has been designed and synthesized, and their structure/properties relationships have been investigated. Whereas these molecules have a V-shaped bent conformation in the ground state, the bent structure changes to a planar conformation in the lowest excited singlet (S-1) state irrespective of the lengths of the aceneimide wings. However, the fluorescence behavior in solution is distinct between the naphthaleneimide system and the anthraceneimide system. The former has a nonemissive S-1 state owing to the significant contribution of the antiaromatic character of the planar COT frontier molecular orbitals, thereby resulting in complete fluorescence quenching in solution. In contrast, the latter anthraceneimide system shows an intense emission, which is ascribed to the planar but distorted S-1 state that shows the allowed transition between the -molecular orbitals delocalized over the COT core and the acene wings. The other characteristic of these systems is the significantly redshifted fluorescence in the crystalline state relative to their monomer fluorescence. The relationship between the packing structures and the fluorescence properties was investigated by preparing a series of hybrid systems with different sizes of substituents on the imide moieties, which revealed the effect of the twofold -stacked structure of the V-shaped molecules on the large bathochromic shift in emission.

    DOI: 10.1002/chem.201303955

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  130. Hydroxyphenyl-Substituted Benzophosphole Oxides: Impact of the Intramolecular Hydrogen Bond on the Fluorescence Properties

    Fukazawa Aiko, Osaki Hiroshi, Yamaguchi Shigehiro

    ASIAN JOURNAL OF ORGANIC CHEMISTRY   Vol. 3 ( 2 ) page: 122 - 127   2014.2

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  131. Hydroxyphenyl-Substituted Benzophosphole Oxides: Impact of the Intramolecular Hydrogen Bond on the Fluorescence Properties Reviewed

    Aiko Fukazawa, Hiroshi Osaki, Shigehiro Yamaguchi

    ASIAN JOURNAL OF ORGANIC CHEMISTRY   Vol. 3 ( 2 ) page: 122 - 127   2014.2

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    DOI: 10.1002/ajoc.201300227

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  132. COD ID: 4120128 Reviewed

    Nagura Kazuhiko, Saito Shohei, Yusa Hitoshi, Yamawaki Hiroshi, Fujihisa Hiroshi, Sato Hiroyasu, Shimoikeda Yuichi, Yamaguchi Shigehiro

    Crystallography Open Database     2014

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  133. Constraint-induced structural deformation of planarized triphenylboranes in the excited state Reviewed

    Tomokatsu Kushida, Cristopher Camacho, Ayumi Shuto, Stephan Irle, Masayasu Muramatsu, Tetsuro Katayama, Syoji Ito, Yutaka Nagasawa, Hiroshi Miyasaka, Eri Sakuda, Noboru Kitamura, Zhiguo Zhou, Atsushi Wakamiya, Shigehiro Yamaguchi

    CHEMICAL SCIENCE   Vol. 5 ( 4 ) page: 1296 - 1304   2014

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    Triphenylboranes planarized with three methylene bridges exhibited dual fluorescence bands around 340 and 400 nm despite their structural constraint. To elucidate the origin, their excited state dynamics were experimentally and theoretically studied. The measurements of fluorescence lifetimes and transient absorption spectra indicated that the planarized triphenylboranes adopt two local minimum structures in the lowest-energy excited singlet (S-1) state. The TD-DFT potential energy surface of the S-1 state possesses at least two minimum energy structures associated with a planar and a bowl-shaped molecular structure. The theoretical S-1-S-0 transition energies at these geometries were in good agreement with the experimentally observed values. These results indicated that the plane-to-bowl structural relaxation in the S-1 state is the origin of the dual fluorescence. Based on the calculated partial atomic charge on the boron atom, the structural deformation to the bowl-shaped structure results in an increase in the electron density on the boron center. Thus, the enhanced intramolecular charge-transfer character plays a role in this structural deformation. Similar behavior was also observed for trigonally pi-expanded planarized borane derivatives. These results provide an important implication that structural constraint in a planar fashion is not only a strategy to construct a rigid skeleton, but also a viable mechanism to impart flexibility to the skeleton.

    DOI: 10.1039/c3sc52751d

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  134. pi-Extended Planarized Triphenylboranes with Thiophene Spacers

    Ayumi Shuto, Tomokatsu Kushida, Tatsuya Fukushima, Hironori Kaji, Shigehiro Yamaguchi

    ORGANIC LETTERS   Vol. 15 ( 24 ) page: 6234 - 6237   2013.12

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    Planarized triphenylboranes extended with thiophene or bithiophene spacers were synthesized, which showed intense fluorescences in solution and reversible redox waves for reduction in cyclic voltammetry. Organic light-emitting diodes (OLEDs) using these compounds as an electron-transporting material were fabricated.

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  135. Modification and Unexpected Reactivity of 2-Borylbenzaldimines: Acylated and Silylated Derivatives as Well as Dimeric Compounds

    Benedikt Neue, Atsushi Wakarniya, Roland Froehlich, Birgit Wibbeling, Shigehiro Yamaguchi, Ernst-Ulrich Wuerthwein

    JOURNAL OF ORGANIC CHEMISTRY   Vol. 78 ( 23 ) page: 11747 - 11755   2013.12

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    Various novel N-alkyl and N-benzyl 2-borylbenzaldimines 3 were prepared by condensation of 2-(dimesitylboryl)benzaldehyde (1) with amines. Further functionalization of compound 3e was possible by deprotonation and subsequent regioselective reaction with electrophiles to give compounds 4. Applying similar conditions to 3a led to the unexpected formation of hitherto unknown dimeric compounds (5 and 6). All structural types were fully characterized, including by X-ray diffraction (XRD). Furthermore, quantum chemical calculations on the SCS-MP2 and DFT levels gave insights into the reaction mechanisms and the stereoselectivity. The BIN bonding situation in these molecules was analyzed using Wiberg bond indices. Preliminary UV-vis and fluorescence measurements indicate that the substitution reaction leading to compounds 4 can be utilized to tune the photophysical properties of these compounds.

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  136. A Radical Anion of Structurally Constrained Triphenylborane

    Tomokatsu Kushida, Shigehiro Yamaguchi

    ORGANOMETALLICS   Vol. 32 ( 22 ) page: 6654 - 6657   2013.11

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    Chemical reduction of the structurally constrained triphenylborane 1 with K produced a radical anion. EPR analysis demonstrated the delocalization of the unpaired electron spin density over the entire pi skeleton to a greater extent than is the case for a nonconstrained Ph3B radical anion. DFT calculations indicated that the coplanarization of the benzene rings with the boron plane and the shortening of the B-C bond lengths by the structural constraint are responsible for the spin delocalization. The geometry optimization also suggested a bowl-shaped conformation as a viable local minimum structure in addition to the planar conformation. X-ray crystal structure analysis indeed revealed the nonplanar structure of the radical anion 1(center dot-).

    DOI: 10.1021/om400560u

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  137. Diarylated Bi(thieno[2,3-c]thiophene)s: A Ring-Fusing Strategy for Controlling the Molecular Alignment of Oligoarenes Reviewed

    Aiko Fukazawa, Daisuke Kishi, Yuki Tanaka, Shu Seki, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 52 ( 46 ) page: 12091 - 12095   2013.11

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    DOI: 10.1002/anie.201306323

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  138. Constraint-induced Structural Deformation of Planarized Triphenylboranes in the Excited State Reviewed

    T. Kushida, C. Camacho, A. Shuto, S. Irle, M. Muramatsu, T. Katayama, S. Ito, Y. Nagasawa, H. Miyasaka, E. Sakuda, N. Kitamura, Z. Zhou, A. Wakamiya, and S. Yamaguchi

    Chem. Sci.   Vol. 5   page: 1296-1304   2013.11

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    DOI: DOI: 10.1039/C3SC52751D

  139. Photochemical Double 5-exo Cyclization of Alkenyl-Substituted Dithienylacetylenes: Efficient Synthesis of Diarylated Dithienofulvalenes Reviewed

    Aiko Fukazawa, Takashi Karasawa, Hongyu Zhang, Kazumitsu Minemura, Cristopher Camacho, Jian Wang, Stephan Irle, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 52 ( 40 ) page: 10519 - 10523   2013.9

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    Smooth and selective: Upon photoirradiation, bis(3-alkenyl-2-thienyl) acetylenes smoothly and selectively undergo double 5-exo-dig cyclization to produce a series of thiophene-fused pentafulvalenes with various aryl substituents. In this fused π-conjugated skeleton, the fused thiophene rings and the aryl substituents significantly modulate the electronic structure of the pentafulvalene skeleton. Copyright © 2013 WILEY-VCH Verlag GmbH &amp
    Co. KGaA, Weinheim.

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  140. Diarylated Bi(thieno[2,3-c]thiophene)s: A Ring-fusing Strategy for Controlling the Molecular Alignment of Oligoarenes Reviewed

    A. Fukazawa, D. Kishi, Y. Tanaka, S. Seki, and S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 52   page: 12091-12095   2013.9

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    DOI: DOI: 10.1002/anie.201306323

  141. Photochemical Double 5-exo-dig Cyclization of Alkenyl-substituted Dithienylacetylenes: Efficient Synthesis of Diarylated Dithienofulvalenes Reviewed

    A. Fukazawa, T. Karasawa, H. Zhang, K. Minemura, C. Camacho, J. Wang, S. Irle, and S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 52   page: 10519-10523   2013.8

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    DOI: DOI: 10.1002/anie.201303738

  142. Amplified Spontaneous Emission in Pentathienoacene Dioxides by Direct Optical Pump and by Energy Transfer: Correlation with Photophysical Parameters

    Juan Casado, Victor Hernandez, Juan T. Lopez Navarrete, Manuel Algarra, Demetrio A. da Silva Filho, Shigehiro Yamaguchi, Raquel Rondao, J. Sergio Seixas de Melo, Victor Navarro-Fuster, Pedro G. Boj, Maria A. Diaz-Garcia

    ADVANCED OPTICAL MATERIALS   Vol. 1 ( 8 ) page: 588 - 599   2013.8

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    Amplified spontaneous emission (ASE) is observed, under optical pump, in polystyrene films doped with two pentathienoacene derivatives functionalised with thienyl-S, S-dioxide groups (compounds 2 and 3). The effect of the dioxide groups on the ASE properties is analysed by comparing the performance with that of its corresponding non-oxidized analogue (1). Films containing either 2 or 3 show ASE at 511 and 574 nm, respectively, when excited directly (at 435 nm) on their absorption bands, showing thresholds and linewidths larger than those obtained from films doped with 1, pumped at 355 nm. ASE is also observed under excitation at 355 nm, in samples containing 1 (host) and either 2 or 3 (guests), due to energy transfer from host to guest. For the blends with 3, the ASE threshold is lower than that obtained when the films are excited directly. Results are interpreted in terms of the photophysical parameters such as absorption capacity, fluorescence efficiency, singlet-to-triplet intersystem crossing leading to triplet-triplet re-absorptions, bimolecular energy-transfer efficiency, efficiency of internal conversion process, etc. State-of-the-art quantum chemical calculations are used in the interpretation of the experimental results.

    DOI: 10.1002/adom.201300155

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  143. Boracyclophanes: Modulation of the sigma/Character in Boron-Benzene Interactions

    Tomokatsu Kushida, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 52 ( 31 ) page: 8054 - 8058   2013.7

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    DOI: 10.1002/anie.201303830

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  144. Distinct Responses to Mechanical Grinding and Hydrostatic Pressure in Luminescent Chromism of Tetrathiazolylthiophene Reviewed

    K. Nagura, S. Saito, H. Yusa, H. Yamawaki, H. Fujihisa, H. Sato, Y. Shimoikeda, and S. Yamaguchi

    J. Am. Chem. Soc.   Vol. 135   page: 10322-10325   2013.7

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    DOI: DOI: 10.1021/ja4055228

  145. Distinct Responses to Mechanical Grinding and Hydrostatic Pressure in Luminescent Chromism of Tetrathiazolylthiophene Reviewed

    Kazuhiko Nagura, Shohei Saito, Hitoshi Yusa, Hiroshi Yamawaki, Hiroshi Fujihisa, Hiroyasu Sato, Yuichi Shimoikeda, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 135 ( 28 ) page: 10322 - 10325   2013.7

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    Luminescent mechanochromism has been intensively studied in the past few years. However, the difference in the anisotropic grinding and the isotropic compression is not clearly distinguished in many cases, in spite of the importance of this discrimination for the application of such mechanochromic materials. We now report the distinct luminescent responses of a new organic fluorophore, tetrathiazolylthiophene, to these stresses. The multichromism is achieved over the entire visible region using the single fluorophore. The different mechanisms of a blue shift by grinding crystals and of a red shift under hydrostatic pressure are fully investigated, which includes a high-pressure single-crystal X-ray diffraction analysis. The anisotropic and isotropic modes of mechanical loading suppress and enhance the excimer formation, respectively, in the 3D hydrogen-bond network.

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  146. A Pentacoordinate Boron-Containing pi-Electron System with CI-B-CI Three-Center Four-Electron Bonds Reviewed

    Chuandong Dou, Shohei Saito, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 135 ( 25 ) page: 9346 - 9349   2013.6

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    Tricoordinate boron-containing pi-electron systems are an attractive class of compounds with intense fluorescence and strong electron-accepting properties. However, the impact of pentacoordination of the boron atoms on their properties has not been determined. We now disclose a B,B'-bis(1,8-dichloro-9-anthryl)-substituted 9,10-dihydro-9,10-diboraanthracene as a new pentacoordinate organoboron compound. In this skeleton, with the aid of the orthogonal arrangement of the anthryl substituent, the B and Cl atoms can form a three-center four-electron (3c-4e) Cl-B-Cl bond. The pentacoordination of the boron atom significantly perturbs the electronic structure and thereby the photophysical and electrochemical properties.

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  147. A pi-Conjugated System with Flexibility and Rigidity That Shows Environment-Dependent RGB Luminescence Reviewed

    Chunxue Yuan, Shohei Saito, Cristopher Camacho, Stephan Irle, Ichiro Hisaki, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 135 ( 24 ) page: 8842 - 8845   2013.6

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    We have designed and synthesized a pi-conjugated system that consists of a flexible and nonplanar pi joint and two emissive rigid and planar wings. This molecular system exhibits respectively red, green, and blue (RGB) emission from a single-component luminophore in different environments, namely in polymer matrix, in solution, and in crystals. The flexible unit gives rise to a dynamic conformational change in the excited state from a nonplanar V-shaped structure to a planar structure, leading to a dual fluorescence of blue and green colors. The rigid and planar moieties favor the formation of a two-fold pi-stacked array of the V-shaped molecules in the crystalline state, which produces a red excimer-like emission. These E RGB emissions are attained without changing the excitation energy.

    DOI: 10.1021/ja404198h

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  148. A π-Conjugated System with Flexibility and Rigidity that Shows Environment-Dependent RGB Luminescence Reviewed

    C. Yuan, S. Saito, C. Camacho, S. Irle, I. Hisaki, and S. Yamaguchi

    J. Am. Chem. Soc.   Vol. 135   page: 8842-8845   2013.5

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    DOI: DOI: 10.1021/ja404198h

  149. Fluorescent Modular Boron Systems Based on NNN- and ONO-Tridentate Ligands: Self-Assembly and Cell Imaging Reviewed

    Christoph Glotzbach, Ulrike Kauscher, Jens Voskuhl, N. Seda Kehr, Marc C. A. Stuart, Roland Froehlich, Hans J. Galla, Bart Jan Ravoo, Kazuhiko Nagura, Shohei Saito, Shigehiro Yamaguchi, Ernst-Ulrich Wuerthwein

    JOURNAL OF ORGANIC CHEMISTRY   Vol. 78 ( 9 ) page: 4410 - 4418   2013.5

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    We have synthesized a series of new fluorescent boron systems 1a-c and 2a-d based on nitrogen (NNN) or nitrogen and oxygen (ONO)-containing tridentate ligands. These novel dyes are characterized by high thermal and chemical stability. They show large Stokes shifts (mostly above 3200 cm(-1)) and quantum yields in solution and in the solid state up to 40%. The easy, modular synthesis facilitates the convenient variation of the axial substituent on the central boron atom, allowing the functionalization of this dye for biochemical use. Introducing a long alkyl chain with a phenyl spacer at this axial position enables the self-assembly of the boron compound 2d to form a fluorescent vesicle, which is able to encapsulate small molecules such as sulforhodamine. Additionally, boron compound 2d was found to serve as a dye for cell imaging since it has the capability of binding to the nuclear membranes of HeLa cells. With phospholipids such as DOPC, giant unilamelar vesicles (GUV) are formed. These results demonstrate the wide applicability of this new boron system in supramolecular and medicinal chemistry.

    DOI: 10.1021/jo4003745

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  150. Borylated Dibenzoborepin Synthesized via Skeletal Rearrangement and its Photochromism Based on Bora-Nazarov Cyclization Reviewed

    A. Iida, S. Saito, T. Sasamori, and S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 52   page: 3760-3764   2013.2

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    DOI: DOI: 10.1002/anie.201210236

  151. Borylated Dibenzoborepin Synthesized via Skeletal Rearrangement and its Photochromism Based on Bora-Nazarov Cyclization Reviewed

    A. Iida, S. Saito, T. Sasamori, S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 52   page: 3760-3764   2013.2

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  152. Thiophene-Fused Bisdehydro[12]annulene That Undergoes Transannular Alkyne Cycloaddition by Either Light or Heat

    Fukazawa Aiko, Oshima Hiroya, Shiota Yoshihito, Takahashi Shouya, Yoshizawa Kazunari, Yamaguchi Shigehiro

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 135 ( 5 ) page: 1731 - 1734   2013.2

  153. Sequential Electrophilic and Photochemical Cyclizations from Bis(bithienyl)acetylene to a Tetrathienonaphthalene Core Reviewed

    Chuandong Dou, Shohei Saito, Libin Gao, Naoki Matsusumoto, Takashi Karasawa, Hongyu Zhang, Aiko Fukazawa, Shigehiro Yamaguchi

    ORGANIC LETTERS   Vol. 15 ( 1 ) page: 80 - 83   2013.1

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    Photoirradiation of bis(bithienyl)acetylenes in the presence of iodine undergoes sequential electrophilic and photochemical cyclizations to produce tetrathienonaphthalenes (TTN) in one pot. The UN framework is readily transformed into cruciform pi-extended derivatives, which form ordered nano/microstructures.

    DOI: 10.1021/ol303107y

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  154. Thermal 8 pi electrocyclic reaction of heteroarene tetramers: new efficient access to pi-extended cyclooctatetraenes Reviewed

    Kazuhiro Mouri, Shohei Saito, Ichiro Hisaki, Shigehiro Yamaguchi

    CHEMICAL SCIENCE   Vol. 4 ( 12 ) page: 4465 - 4469   2013

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    Bromo-substituted acyclic thiazole tetramers selectively underwent an 8 pi thermal electrocyclic reaction at high temperatures of 280-300 degrees C without solvent, producing p-extended thiazole-fused cyclooctatetraenes (COTs) in high yields. A quantum chemical study provided a rationale for the lower activation barrier and high selectivity of the 8 pi electrocyclic reaction mode over a competitive 6 pi electrocyclic reaction. The terminal bromine atom acts as a leaving group to trigger the rearomatization of the electrocyclized intermediate, which leads to the formation of the energetically stable COT products. This synthetic protocol enables us to synthesize a series of thiazole-fused COTs, including a derivative that can form loosely stacked columnar arrays in the crystalline state and shows fluorescence in the solid state.

    DOI: 10.1039/c3sc52232f

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  155. S-Pechmann dye: a thiolactone-containing organic dye with a pronounced electron-accepting character and its solid-state photophysical properties Reviewed

    Aiko Fukazawa, Makoto Adachi, Ken Nakakura, Shohei Saito, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 49 ( 64 ) page: 7117 - 7119   2013

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    A sulfur analogue of a Pechmann dye has been synthesized. In addition to long-wavelength absorption and fluorescence, it showed multiple redox processes with low reduction potentials in cyclic voltammetry. The size effect of sulfur is responsible for its enhanced electron-accepting character.

    DOI: 10.1039/c3cc41007b

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  156. Dibenzopentalenes from B(C6F5)(3)-Induced Cyclization Reactions of 1,2-Bis(phenylethynyl)benzenes Reviewed

    Chao Chen, Marcel Harhausen, Rene Liedtke, Kathrin Bussmann, Aiko Fukazawa, Shigehiro Yamaguchi, Jeffrey L. Petersen, Constantin G. Daniliuc, Roland Froehlich, Gerald Kehr, Gerhard Erker

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 52 ( 23 ) page: 5992 - 5996   2013

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    DOI: 10.1002/anie.201300871

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  157. Benzene-fused BODIPY and fully-fused BODIPY dimer: impacts of the ring-fusing at the b bond in the BODIPY skeleton Reviewed

    Atsushi Wakamiya, Takanori Murakami, Shigehiro Yamaguchi

    CHEMICAL SCIENCE   Vol. 4 ( 3 ) page: 1002 - 1007   2013

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    4,4-Difluoro-4-bora-3a, 4a-diaza-s-indacenes (BODIPYs) are fascinating dyes with great potentials for various applications. To establish the design principle for the modification of the BODIPY skeleton, we now investigate the electronic impacts of the introduction of ring-fused structures. The DFT calculations revealed that while the benzene-fusing at the a bond in the BODIPY skeleton increases the HOMO level, the benzene-fusing at the b bond leads to a decreased LUMO level. Based on these results, a benzo[b]fused BODIPY 1 and a fully-fused BODIPY dimer 2 were synthesized. X-ray crystal structure analysis demonstrated that the benzo[b]-fused structure significantly perturbs the pi-conjugation with enhancement of an electron-accepting azafulvene character. In the ring-fused BODIPY dimer 2, the central benzene ring is largely deviated from the aromatic benzene geometry. As a consequence, 2 has a significantly low-lying LUMO delocalized along the periphery. In cyclic voltammograms, the benzene-fused BODIPY 1 and fully-fused dimer 2 indeed showed reversible reduction waves at much less negative potentials (E-1/2 = -1.05 V vs. Fc/Fc(+) for 1, -0.85 V for 2), relative to a non-fused BODIPY 3 (E-1/2 = -1.40 V). In addition, the benzene-fused BODIPYs showed broad and intense absorption bands in the Vis-NIR region. In particular, the BODIPY dimer 2 showed an intense absorption at 629 nm with a broad shoulder band reaching 900 nm. Corresponding to the red-shifted absorption, compounds 1 and 2 showed weak fluorescence in the deep red region (lambda(em) = 690 nm, Phi(F) < 0.01) and in the near-infrared region (940 nm, Phi(F) < 0.01), respectively.

    DOI: 10.1039/c2sc21768f

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  158. Borylated Dibenzoborepin: Synthesis by Skeletal Rearrangement and Photochromism Based on Bora-Nazarov Cyclization Reviewed

    Azusa Iida, Shohei Saito, Takahiro Sasamori, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 52 ( 13 ) page: 3760 - 3764   2013

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    DOI: 10.1002/anie.201210236

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  159. Modulating the Photoisomerization of N,C-Chelate Organoboranes with Triplet Acceptors

    Zachary M. Hudson, Soo-Byung Ko, Shigehiro Yamaguchi, Suning Wang

    ORGANIC LETTERS   Vol. 14 ( 21 ) page: 5610 - 5613   2012.11

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    Triplet acceptors such as naphthalene, pyrene, and anthracene have been found to be highly effective in controlling the photoisomerization efficiency of N,C-chelate boryl chromophores, establishing the involvement of a photoactive triplet state in the isomerization of this class of photochromic compounds.

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  160. Boron-Containing PAH as a Substructure of Boron-Doped Graphene Reviewed

    C. Dou, S. Saito, K. Matsuo, I. Hisaki, and S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 51   page: 12206-12210   2012.10

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    DOI: DOI: 10.1002/anie.201206699

  161. TICT Fluorescence of N-borylated 2,5-Diarylpyrroles: A Gear Like Dual Motion in the Excited State Reviewed

    T. Taniguchi, J. Wang, S. Irle, and S. Yamaguchi

    Dalton Trans.   Vol. 42   page: 620-624   2012.10

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    DOI: 10.1039/C2DT32134C

  162. Polycyclic pi-Electron System with Boron at Its Center Reviewed

    Shohei Saito, Kyohei Matsuo, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 134 ( 22 ) page: 9130 - 9133   2012.6

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    We disclose a new planarized triarylborane in which the tri-coordinated boron atom is embedded in a fully fused polycyclic pi-conjugated skeleton. The compound shows high stability toward oxygen, water, and silica gel, despite the absence of steric protection around the B atom. Reflecting the electron-donating character of the pi-skeleton and the electron-accepting character of the B atom, this compound shows broad absorption bands that cover the entire visible region and a fluorescence in the visible/near-IR region. In addition, this compound shows dramatic property changes upon formation of a tetra-coordinated borate, such as thermochromic behavior in the presence of pyridine.

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  163. Elucidation of p-Conjugation Modes in Diarene-Fused 1,2-Dihydro-1,2-diborin Dianions Reviewed

    Takafumi Araki, Atsushi Wakamiya, Kenji Mori, Shigehiro Yamaguchi

    CHEMISTRY-AN ASIAN JOURNAL   Vol. 7 ( 7 ) page: 1594 - 1603   2012.6

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    A series of diarene-fused 1,2-dihydro-1,2-diborins were prepared as a new B?B-bond-embedded polycyclic p-electron system. The reduction of these compounds with metals produced their corresponding dianions, the p-conjugation modes of which varied from 6p-conjugation within the central 1,2-diborin skeleton to 14p peripheral conjugation over the tricyclic skeleton, depending on the nature of the reduced biaryl framework. Moreover, the countercation to the dianions had a significant effect on the absorption spectra, with a dramatic color change from yellow to deep blue, depending on the distance between the tricyclic dianion skeleton and the countercation.

    DOI: 10.1002/asia.201200055

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  164. Polycyclic π-Electron System with Boron at Its Center Reviewed

    S. Saito, K. Matsuo, and S. Yamaguchi

    J. Am. Chem. Soc.   Vol. 134   page: 9130-9133   2012.5

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    DOI: DOI: 10.1021/ja3036042

  165. Preparation of Dihydroborole Derivatives by a Simple 1,1-Carboboration Route

    Andreas Feldmann, Azusa Iida, Roland Froehlich, Shigehiro Yamaguchi, Gerald Kehr, Gerhard Erker

    ORGANOMETALLICS   Vol. 31 ( 6 ) page: 2445 - 2451   2012.3

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    2,3-Dihydroboroles are readily formed by treatment of dicyclopropylacetylene with the strongly electrophilic borane B(C6F5)(3). The reaction involves a sequence of 1,1-carboboration reactions and proceeds via dienylborane intermediates. Consistent with this, the reaction of the conjugated enyne 15c with B(C6F5)(3) leads to the formation of a dihydroborole.

    DOI: 10.1021/om300065m

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  166. Planarized Triarylboranes: Stabilization by Structural Constraint and Their Plane-to-Bowl Conversion Reviewed

    Zhiguo Zhou, Atsushi Wakamiya, Tomokatsu Kushida, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 134 ( 10 ) page: 4529 - 4532   2012.3

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    Triphenylborane and 9,10-diphenyl-9,10-dihydro-9,10-diboraanthracene, constrained to a planar arrangement with methylene tethers, were synthesized by intramolecular multi-fold Friedel-Crafts cyclization. These compounds were stable toward air, water, and amines, despite the absence of steric protection in the vertical direction with respect to the B atoms, and showed characteristic structural, electronic, and photophysical properties. In addition, upon treatment with a fluoride ion, these compounds underwent a plane-to-bowl conversion in a controlled manner.

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  167. Synthesis and Photophysical Properties of Aryl-Substituted 2-Borylbenzaldimines and Their Extended pi-Conjugated Congeners Reviewed

    Benedikt Neue, Roland Froehlich, Birgit Wibbeling, Aiko Fukazawa, Atsushi Wakamiya, Shigehiro Yamaguchi, Ernst-Ulrich Wuerthwein

    JOURNAL OF ORGANIC CHEMISTRY   Vol. 77 ( 5 ) page: 2176 - 2184   2012.3

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    Novel N-aryl-substituted 2-borylbenzaldimines 6 and related systems with extended pi-framework 7 based on two borylbenzaldimine units linked by a spacer moiety were synthesized by condensation reactions of 2-(dimesitylboryl)benzaldehyde 3 with various amines 4 and diamines 5. All compounds were completely characterized including X-ray diffraction, especially in view of Lewis acid-base B-O and B-N interactions. The electronic as well as the photophysical properties of bisimines 7 were determined using cyclic voltammetry, UV/vis, and fluorescence spectroscopy and quantum chemistry. These compounds feature large Stokes shifts and reversible reduction waves. Interestingly, UV irradiation experiments unfold enhanced photostability for compounds 7 with an extended pi-skeleton. By use of 1,8-diaminonaphthalene we observed the formation of a hitherto unknown BN-heterocyclic compound 9 fused with a perimidine skeleton. Structural and energetic aspects were evaluated by high level quantum chemical methods (DFT and SCS-MP2-calculations).

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  168. Planarized Triarylboranes: Stabilization by Structural Constraint and Their Plane-to-Bowl Conversion Reviewed

    Z. Zhou, A. Wakamiya, T. Kushida, and S. Yamaguchi

    J. Am. Chem. Soc.   Vol. 134   page: 4529-4532   2012.2

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    DOI: DOI: 10.1021/ja211944q

  169. Substituent Effects on Twisted Internal Charge Transfer Excited States of N-Borylated Carbazoles and (Diphenylamino)boranes

    Jian Wang, Ying Wang, Takuhiro Taniguchi, Shigehiro Yamaguchi, Stephan Irle

    JOURNAL OF PHYSICAL CHEMISTRY A   Vol. 116 ( 4 ) page: 1151 - 1158   2012.2

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    N-Boryl-substituted carbazoles (carBR(2)) and (diphenylamino)boranes (Ph2NBR2) with R = Mes (mesityl) and FMes [tris(trifluoromethyl)phenyl] substituents on boron exhibit large UV/vis Stokes shifts. To investigate the substituent effect on the magnitude of the Stokes shifts, we studied the electronic structure and spectroscopic properties of carBR(2) and Ph2NBR2 with R = H, Mes, and FMes using hybrid density functional theory (B3LYP) and time-dependent density functional theory (TD-B3LYP) for ground and low-lying excited states. The lowest lying excited state with a nonvanishing oscillator strength is a twisted internal charge transfer (TICT) (1)A state in the C-2 point group, owing to a single-electron excitation from the nitrogen lone pair to the unoccupied boron p(z) AO, Nlp -> Bp(z). Emission from these (1)A excited states are predicted to be much brighter than from the energetically close B-1 excited states that are not directly related to CT excitation from N to B, due to symmetry. An analysis of geometrical relaxations in the excited state and the state energies relative to the ground state energy of the equilibrium geometry reveals that (a) the carbazole skeleton induces a general red shift in UV/vis spectra, (b) bulky boryl substituents reduce the predicted Stokes shifts of TICT states, and (c) the presence of electron-withdrawing functional groups induces a further general red shift in UV/vis spectra but does not significantly alter Stokes shifts.

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  170. Facile Synthesis of Biphenyl-Fused BODIPY and Its Property Reviewed

    Yosuke Hayashi, Naoki Obata, Masatomo Tamaru, Shigeru Yamaguchi, Yutaka Matsuo, Akinori Saeki, Shu Seki, Yuka Kureishi, Shohei Saito, Shigehiro Yamaguchi, Hiroshi Shinokubo

    ORGANIC LETTERS   Vol. 14 ( 3 ) page: 866 - 869   2012.2

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    A biphenyl-fused BODIPY was synthesized through a facile oxidative cyclization of peripheral aryl-substituents at the beta-position of the BODIPY unit. The extended pi-system of the fused BODIPY induces near-infrared (NIR) absorption and strong pi-pi interactions in the solid state. These features are beneficial for the application of the dye as a functional material. The biphenyl-fused BODIPY dye was demonstrated to exhibit photocurrent conversion ability on the basis of its n-type semiconducting property.

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  171. Planarized B-phenylborataanthracene anions: structural and electronic impacts of coplanar constraint Reviewed

    Tomokatsu Kushida, Zhiguo Zhou, Atsushi Wakamiya, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   Vol. 48 ( 87 ) page: 10715 - 10717   2012

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    Potassium and lithium salts of anionic B-phenylborataanthracenes, whose phenyl groups were fixed in a coplanar fashion, were synthesized. These compounds exhibited solvent-separated ion pair structures both in the crystalline state and in solution. Planarization of the phenyl moiety had a remarkable impact on the photophysical properties, such as the red-shifted absorption and intense fluorescence.

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  172. Macrocyclic Restriction with Flexible Alkylene Linkers: A Simple Strategy to Control the Solid-State Properties of pi-Conjugated Systems Reviewed

    Shohei Saito, Ken Nakakura, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 51 ( 3 ) page: 714 - 717   2012

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    DOI: 10.1002/anie.201107172

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  173. N-Heterocyclic Carbene Boranes as Electron-Donating and Electron-Accepting Components of pi-Conjugated Systems Reviewed

    Kazuhiko Nagura, Shohei Saito, Roland Froehlich, Frank Glorius, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 51 ( 31 ) page: 7762 - 7766   2012

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    DOI: 10.1002/anie.201204050

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  174. Highly Flexible pi-Expanded Cyclooctatetraenes: Cyclic Thiazole Tetramers with Head-to-Tail Connection Reviewed

    Kazuhiro Mouri, Shohei Saito, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 51 ( 24 ) page: 5971 - 5975   2012

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    DOI: 10.1002/anie.201201265

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  175. Combined experimental and theoretical studies on the photophysical properties of cycloparaphenylenes Reviewed

    Yasutomo Segawa, Aiko Fukazawa, Sanae Matsuura, Haruka Omachi, Shigehiro Yamaguchi, Stephan Irle, Kenichiro Itami

    ORGANIC & BIOMOLECULAR CHEMISTRY   Vol. 10 ( 30 ) page: 5979 - 5984   2012

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    We studied the UV-vis absorption and fluorescence in solution/solid states of [n]cycloparaphenylene ([n] CPP: n = 9, 12, 14, 15, and 16), and conducted theoretical studies to better understand the experimental results. The representative experimental findings include (i) the most intense absorption maxima (lambda(abs1)) display remarkably close values (338-339 nm), (ii) the longest-wavelength absorption maxima (lambda(abs2)) are blue-shifted with increasing the ring size (395 --> 365 nm), (iii) the emission maxima (lambda(em)) are blue-shifted with increasing the ring size (494 --> 438 nm for longest-wavelength maxima), (iv) the fluorescent quantum yields (Phi(F)) in solution are high (0.73-0.90), (v) the fluorescence lifetimes (tau(s)) of [9]- and [12] CPP are 10.6 and 2.2 ns, respectively, and (vi) the Phi(F) values slightly increase in polymer matrix but significantly decrease in the crystalline state. According to TD-DFT calculations, the longest-wavelength absorption (lambda(abs2)) corresponds to a forbidden HOMO --> LUMO transition and the most intense absorption (lambda(abs1)) corresponds to degenerate HOMO - 1 --> LUMO and HOMO --> LUMO + 1 transitions with high oscillator strength. The interesting and counterintuitive optical properties of CPPs (constant lambda(abs1) and blue shift of lambda(abs2)) could be ascribed mainly to the ring-size effect in frontier molecular orbitals (in particular the increase of the HOMO-LUMO gap as the number of benzene rings increases). On the basis of comparative calculations using hypothetical model geometries, we conclude that the unique behavior of HOMO and LUMO of CPPs is due mainly to their lack of a conjugation length dependence in combination with a significant bending effect (particularly to HOMO) and a torsion effect (particularly to LUMO).

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  176. Electron-Donating Tetrathienyl-Substituted Borole Reviewed

    Takafumi Araki, Aiko Fukazawa, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 51 ( 22 ) page: 5484 - 5487   2012

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    DOI: 10.1002/anie.201201156

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  177. Heteroarene-fused boroles: what governs the antiaromaticity and Lewis acidity of the borole skeleton?

    Azusa Iida, Anna Sekioka, Shigehiro Yamaguchi

    CHEMICAL SCIENCE   Vol. 3 ( 5 ) page: 1461 - 1466   2012

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    A series of benzoheteroarene-fused boroles, containing pyrrole, furan, and thiophene as the heteroarene rings, were synthesized and their structures were determined by X-ray crystallographic analysis. Their antiaromaticity was assessed by calculations of the nucleus-independent chemical shift (NICS) values using the geometries derived from their crystal structures. The large NICS(1)(zz) values of the borole ring in the heteroarene-fused structures showed their high antiaromaticity, in contrast to the fact that dibenzoborole has a reduced antiaromaticity. This enhanced antiaromaticity is due to the lower extent of bond alternation in the borole ring with the heteroarene-fused structures compared to that in the parent borole. Theoretical calculations also indicated that the antiaromatic character of the borole is relevant to its LUMO level. Moreover, the experimentally evaluated Lewis acidities of the heteroarene-fused boroles are linearly correlated to their reduction potentials, namely, the LUMO levels. These results shed light on the understanding of how the fused-structures affect the properties and reactivities of the borole moiety. All the heteroarene-fused boroles have broad absorption bands with the comparable absorption maxima around 468-479 nm. In contrast, their reduction potentials are different from one another, dependent on the electronic characteristics of the heteroarene rings.

    DOI: 10.1039/c2sc20100c

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  178. High-performance organic field-effect transistors based on dihexyl-substituted dibenzo[d,d ']thieno[3,2-b;4,5-b ']dithiophene

    Yasuo Miyata, Eiji Yoshikawa, Takeo Minari, Kazuhito Tsukagoshi, Shigehiro Yamaguchi

    JOURNAL OF MATERIALS CHEMISTRY   Vol. 22 ( 16 ) page: 7715 - 7717   2012

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    A novel thienoacene compound, dihexyl-substituted dibenzo[d,d']thieno[3,2-b;4,5-b']dithiophene (C6-DBTDT), is developed as a p-type organic semiconductor for high-performance organic field-effect transistors. Insertion of an acceptor material at the contact interface enables substantial reduction in the threshold voltage and hysteresis behavior, and the field-effect mobilities of 2.5 and 3.1 cm(2) V-1 s(-1) are achieved for the C6-DBTDT film vacuum-deposited at room temperature and 80 degrees C, respectively.

    DOI: 10.1039/c2jm30840a

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  179. A Boron-Containing PAH as a Substructure of Boron-Doped Graphene Reviewed

    Chuandong Dou, Shohei Saito, Kyohei Matsuo, Ichiro Hisaki, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 51 ( 49 ) page: 12206 - 12210   2012

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    DOI: 10.1002/anie.201206699

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  180. Synthetic Study of Novel pi-Electron Materials Containing Boron, Nitrogen, and Phosphorus as Key Main Group Elements

    Yamaguchi Shigehiro, Fukazawa Aiko

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   Vol. 69 ( 6 ) page: 661 - 670   2011.6

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  181. Synthetic Study of Novel pi-Electron Materials Containing Boron, Nitrogen, and Phosphorus as Key Main Group Elements Reviewed

    Shigehiro Yamaguchi, Aiko Fukazawa

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   Vol. 69 ( 6 ) page: 661 - 670   2011.6

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    Incorporation of main group elements into pi-conjugated skeletons is a powerful strategy for the development of new pi-electron materials with intriguing properties. An important direction in this chemistry may be to exploit synergistic effects of two or more main group elements, which enables us to construct new skeletons with unusual electronic structures. From this point of view, several kinds of pi-conjugated molecules containing B, N, and P have been synthesized, including B-B bond-containing thiophene-fused 1,2-dihydro-1,2-diborin, B-N bond-incorporated pi-extended 1,2-dihydro-1,2-azaborine, and several ladder-type pi-conjugated compounds containing boron and phosphorus as the bridging moieties. In particular, some of the latter compounds have been synthesized based on newly developed intramolecular double cyclizations from o,o'-disubstituted diphenylacetylene precursors. Investigation on their structure-properties relationships revealed the effect of these main group elements on the electronic structures and thus their properties. Some of these compounds showed high potentials for applications as the electron-transporting materials and two-photon absorption materials.

    DOI: 10.5059/yukigoseikyokaishi.69.661

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  182. Thiophene-Fused Ladder Boroles with High Antiaromaticity

    Iida Azusa, Yamaguchi Shigehiro

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 133 ( 18 ) page: 6952 - 6955   2011.5

  183. Design, Synthesis, and Characterization of Functionalized Silepins: High Quantum Yield Blue Emitters Reviewed

    Lauren G. Mercier, Shunsuke Furukawa, Warren E. Piers, Atsushi Wakamiya, Shigehiro Yamaguchi, Masood Parvez, Ross W. Harrington, William Clegg

    ORGANOMETALLICS   Vol. 30 ( 6 ) page: 1719 - 1729   2011.3

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    The synthesis of a family of 1,1-dimethyldibenzo-[bf]silepin derivatives, substituted with. donor groups of various donor strength and conjugation length in the positions meta or para to the silepin silicon, is presented. The compounds were characterized by NMR, UV-vis, and fluorescence spectroscopy, as well as with cyclic voltammetry and DFT computations. One of the meta series was characterized by X-ray crystallography. All compounds show red-shifts in onset absorption and emission maxima compared to the parent 1,1-dimethyldibenzo[bf]silepin, but all exhibit blue fluorescence with quantum yields ranging from 0.46 to 0.93 for the meta series and from 0.09 to 0.46 for the para derivatives. The data suggest that, for the meta series, the primary absorption is of pi-pi* character, while in the para series, for strongly donating groups, transitions from low-lying pi orbitals to the LUMO+1 orbital, which has contributions from the C-Si-C sigma* orbitals, are charge-transfer in character. The phenyl-substituted derivatives can be converted to borepins via transmetalation with BBr3, but other strategies are necessary to prepare borepins with other donor groups.

    DOI: 10.1021/om2000597

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  184. Phosphine Sulfides as an Anchor Unit for Single Molecule Junctions Reviewed

    Aiko Fukazawa, Manabu Kiguchi, Satoshi Tange, Yasunori Ichihashi, Qiang Zhao, Takuya Takahashi, Tatsuya Konishi, Kei Murakoshi, Yuta Tsuji, Aleksandar Staykov, Kazunari Yoshizawa, Shigehiro Yamaguchi

    CHEMISTRY LETTERS   Vol. 40 ( 2 ) page: 174 - 176   2011.2

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    Phenylene and biphenyl compounds with dibenzophosphole sulfide (DBPS) as an anchoring group for single molecule junctions were synthesized. The conductance measurements revealed that the phosphine sulfide indeed acts as an anchoring group for Au electrodes. Theoretical calculations including metal electrodes demonstrated that the LUMO level of the DBPS-terminated biphenyl is close to the Au Fermi level, leading to the electron conduction of the Au-molecule-Au junction based on the resonance-tunneling mechanism.

    DOI: 10.1246/cl.2011.174

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  185. Phosphine Sulfides as an Anchor Unit for Single Molecule Junction Reviewed

    A. Fukazawa, M. Kiguchi, S. Tange, Y. Ichihashi, Q. Zhao, T. Takahashi, T. Konishi, K. Murakoshi, Y. Tsuji, A. Staykov, K. Yoshizawa, and S. Yamaguchi

    Chem. Lett.   Vol. 40   page: 174-176   2011

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  186. Synthesis of 1-Phospha-2-boraacenaphthenes: Reductive 1,2-Aryl Migration of 1-Diarylboryl-8-dichlorophosphinonaphthalenes Reviewed

    Akihiro Tsurusaki, Takahiro Sasamori, Atsushi Wakamiya, Shigehiro Yamaguchi, Kazuhiko Nagura, Stephan Irle, Norihiro Tokitoh

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 50 ( 46 ) page: 10940 - 10943   2011

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    DOI: 10.1002/anie.201104971

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    J-GLOBAL

  187. Bis(phosphoryl)-Bridged Biphenyls by Radical Phosphanylation: Synthesis and Photophysical and Electrochemical Properties Reviewed

    Achim Bruch, Aiko Fukazawa, Eriko Yamaguchi, Shigehiro Yamaguchi, Armido Studer

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 50 ( 50 ) page: 12094 - 12098   2011

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    DOI: 10.1002/anie.201104114

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  188. Electronic Tuning of Thiazolyl-Capped pi-Conjugated Compounds via a Coordination/Cyclization Protocol with B(C6F5)(3) Reviewed

    Andre Job, Atsushi Wakamiya, Gerald Kehr, Gerhard Erker, Shigehiro Yamaguchi

    ORGANIC LETTERS   Vol. 12 ( 23 ) page: 5470 - 5473   2010.12

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    Electronic tuning of thiazolyl-capped pi-conjugated systems via a coordination/cyclization protocol with B(C6F5)(3) effectively enhances an electron-accepting character giving rise to lower reduction potentials and increases thermal stability.

    DOI: 10.1021/ol102282x

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  189. A Study of 1,2-Dihydro-1,2-azaborine in a pi-Conjugated System Reviewed

    Takuhiro Taniguchi, Shigehiro Yamaguchi

    ORGANOMETALLICS   Vol. 29 ( 21 ) page: 5732 - 5735   2010.11

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    The reaction of N-Bac-protected bis(5-phenyl-2-pyrrolyl)borane with BF3 center dot OEt2 produced 3-(phenylpyrrolyl)-6-phenyl- 1,2-dihydro-1,2-azaborine in moderate yield. This compound showed (117 absorption band at a longer wavelength compared to that of its benzene analogue and also exhibited an intense red-shifted fluorescence with a high quantum yield close to unity. According to the X-ray structural analysis, cyclic voltammetry, and theoretical calculations, the 1,2-dihydro-1,2-azaborine acts not like a benzene analogue but like a cyclohexadiene analogue in the extended pi-conjugated skeleton.

    DOI: 10.1021/om100408m

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  190. Intense fluorescence of 1-aryl-2,3,4,5-tetraphenylphosphole oxides in the crystalline state Reviewed

    Aiko Fukazawa, Yasunori Ichihashi, Shigehiro Yamaguchi

    NEW JOURNAL OF CHEMISTRY   Vol. 34 ( 8 ) page: 1537 - 1540   2010

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    A series of 2,3,4,5-tetraphenylphosphole oxides with various aryl groups on the phosphorus atoms were synthesized and their fluorescence properties in the crystalline state were investigated. Some of these compounds showed an intense fluorescence with the quantum yields of 0.75-0.91. These intense emissions are attributable not only to the restricted rotation of the peripheral phenyl rings, but also to the long intermolecular distances between the adjacent molecules in the crystal packing.

    DOI: 10.1039/c0nj00155d

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  191. Thiophene-Fused Phospholo[3,2-b]phospholes and Their Dichalcogenides: Synthesis and Structure-Photophysical Properties Relationships Reviewed

    A. Fukazawa, T. Murai, L. Li, Y. Chen, and S. Yamaguchi

    C. R. Chimie     2010

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    DOI: 10.1016/j.crci.2010.04.021

  192. Neutral and Oxidized Triisopropylsilyl End-Capped Oligothienoacenes: A Combined Electrochemical, Spectroscopic, and Theoretical Study Reviewed

    Juan Arago, Pedro M. Viruela, Enrique Orti, Reyes Malave Osuna, Barbara Vercelli, Gianni Zotti, Victor Hernandez, Juan T. Lopez Navarrete, John T. Henssler, Adam J. Matzger, Yoshitake Suzuki, Shigehiro Yamaguchi

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 16 ( 18 ) page: 5481 - 5491   2010

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    This work presents an analysis of the structural, electrochemical, and optical properties of a family of triisopropylsilyl end-capped oligothienoacenes (TIPS-Tn-TIPS, n=4-8) by combining cyclic voltammetry, spectroscopic techniques, and quantum-chemical calculations. TIPS-Tn-TIPS compounds form stable radical cations, and dications are only obtained for the longest oligomers (n=7 and 8). Oxidation leads to the quinoidization of the conjugated backbone, from which electrons are mainly extracted. The absorption and fluorescence spectra show partially resolved vibronic structures even at room temperature, due to the rigid molecular geometry. Two well-resolved vibronic progressions are observed at low temperatures due to the vibronic coupling, with normal modes showing wavenumbers of approximate to 1525 and approximate to 480 cm(-1). Optical absorption bands display remarkable bathochromic dispersion with the oligomer length, indicative of the extent of pi conjugation. The optical properties of the oxidized compounds are characterized by in situ UV/Vis/NIR spectroelectrochemistry. The radical cation species show two intense absorption bands emerging at energies lower than in the neutral compounds. The formation of the dication is only detected for the heptamer and the octamer. and shows a new band at intermediate energies. Optical data are interpreted with the help of density functional theory calculations performed at the B3LYP/6-31G** level, both for the neutral and the oxidized compounds.

    DOI: 10.1002/chem.200903343

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  193. FT Raman and DFT Study on a Series of All-anti Oligothienoacenes End-Capped with Triisopropylsilyl Groups

    Reyes Malave Osuna, Victor Hernandez, Juan T. Lopez Navarrete, Juan Arago, Pedro M. Viruela, Enrique Orti, Yoshitake Suzuki, Shigehiro Yamaguchi, John T. Henssler, Adam J. Matzger

    CHEMPHYSCHEM   Vol. 10 ( 17 ) page: 3069 - 3076   2009.12

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    Herein, we study the pi-conjugational properties of a homologous series of all-anti oligothienoacenes containing four to eight fused thiophene rings by means of FT Raman spectroscopy and DFT calculations. The theoretical analysis of the spectroscopic data provides evidence that selective enhancement of a very limited number of Raman scatterings is related to the occurrence in these oligothienoacenes of strong vibronic coupling between collective nu(C=C) stretching modes in the 1600-1300 cm(-1) region and the HOMO/LUMO frontier orbitals (HOMO=highest occupied molecular orbital; LUMO=Iowest unoccupied molecular orbital). The correlation of the Raman spectroscopic data and theoretical results for these all-anti oilgothienoacenes with those previously collected for a number of all-syn oligothienohelicenes gives further support to the expectation that cross-conjugation is dominant in heterohelicenes. Fully planar all-anti oligothienoacenes display linear pi conjugation which seemingly does not reach saturation with increasing number of annulated thiophene rings in the oligomeric chain at least up to the octamer.

    DOI: 10.1002/cphc.200900440

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  194. A B-B Bond-Containing Polycyclic pi-Electron System: Dithieno-1,2-dihydro-1,2-diborin and Its Dianion Reviewed

    Atsushi Wakamiya, Kenji Mori, Takafumi Araki, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 131 ( 31 ) page: 10850 - +   2009.8

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    As a B-B bond-containing polycyclic pi-electron system, a dithieno[3,2-c:2',3'-e](1,2-dihydro-1,2-diborin) derivative and its dianion salts were successfully prepared, and their structures were determined by X-ray crystallography. The neutral. dithieno-1,2dihydro-1,2-diborin has a twisted diborin ring in which both the sigma-TT and p-pi* orbital interactions between the bithiophene pi framework and the B-B bond moiety effectively take place, giving rise to an absorption that is significantly red-shifted compared with that of the parent bithiophene. Upon a two-electron reduction, the dithienodiborin pi framework becomes planar and has a characteristic peripheral. pi conjugation through the B-B bond with 14 pi etectrons. Furthermore, the dianion salts show an intriguing countercation effect on their photophysical, properties, indicative of possible etectronic tuning by the countercations.

    DOI: 10.1021/ja905007s

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  195. Intramolecular Reductive Double Cyclization of o,o '-Bis(arylcarbonyl)-diphenylacetylenes: Synthesis of Ladder pi-Conjugated Skeletons

    Hongyu Zhang, Takashi Karasawa, Hiroshi Yamada, Atsushi Wakamiya, Shigehiro Yamaguchi

    ORGANIC LETTERS   Vol. 11 ( 14 ) page: 3076 - 3079   2009.7

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    Upon the treatment of bis(arylcarbonyl)diphenylacetylenes with lithium naphthalenide, the carbonyl reduction dominantly occurs over the acetylene reduction. The produced bis(radical anion) intermediate undergoes a synchronous double-radical 5-endo-dig cyclization. This simple reduction procedure produces two intriguing classes of ladder pi-conjugated skeletons, i.e., emissive methylene-bridged stilbenes and dibenzo[a,e]pentalenes regarded as a cyclic 1,4-diphenylbutadiene.

    DOI: 10.1021/ol901148p

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  196. Structural Modification of Silicon-Bridged Ladder Stilbene Oligomers and Distyrylbenzenes

    Hiroshi Yamada, Caihong Xu, Aiko Fukazawa, Atsushi Wakamiya, Shigehiro Yamaguchi

    MACROMOLECULAR CHEMISTRY AND PHYSICS   Vol. 210 ( 11 ) page: 904 - 916   2009.6

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    Two kinds of the totally alkyl-substituted ladder pi-conjugated compounds, the totally hexyl-substituted silicon-bridged stilbene trimer 1 and the totally propyl-substituted silicon-and carbon-bridged distyrylbenzene 2, were synthesized. X-ray crystallography revealed that both compounds adopt the all-parallel-aligned packing structures through the interpenetration of the alkyl chains with those of the neighboring molecules. The effect of this packing structure on the photophysical properties was investigated. The fluorescence quantum yield measurements showed that both compounds maintained their high quantum yields (Phi(F)) even in the crystalline state (Phi(F) = 0.64 for 1; 0.63 for 2), suggesting the potential effect of the all-parallel alignment for attaining the intense emission in the solid state.

    DOI: 10.1002/macp.200900037

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  197. Long-Lived Exciplex Formation and Delayed Exciton Emission in Bulk Heterojunction Blends of Silole Derivative and Polyfluorene Copolymer: The Role of Morphology on Exciplex Formation and Charge Separation

    Jessica J. Benson-Smith, Joanne Wilson, Clare Dyer-Smith, Kazuhiro Mouri, Shigehiro Yamaguchi, Hideyuki Murata, Jenny Nelson

    JOURNAL OF PHYSICAL CHEMISTRY B   Vol. 113 ( 22 ) page: 7794 - 7799   2009.6

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    Long-lived exciplex emission is observed in blend films of poly[9,9-dioctylfluorene-co-N-(4-methoxyphenyl)diphenylamine] (TFMO) and the soluble silole derivative 2,5-bis-(2,2-bipyridin-6-yl)-1,1-dimethyl-3,4-diphenylsilacyclopentadiene (PyPySPyPy). The exciplex is characterized by a long-lived (similar to 40-90 ns) component in both the photoluminescence and electroluminescence spectra, which is red-shifted relative to the emission of the pristine materials. In addition to exciplex emission, delayed fluorescence from the TFMO singlet state is observed and is attributed to exciton regeneration through the interfacial exciplex state. Comparing blend films made using chlorobenzene and p-xylene solvents, we find that exciplex lifetime and exciton regeneration in the blend film are sensitive to the choice of solvent and the resulting morphology of the blend film. The exciplex emissive lifetime can be correlated to changes in photoluminescence quenching and efficiency of light-emitting diodes.

    DOI: 10.1021/jp808671f

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  198. 3,4-Dihydro-3H-pyrrol-2-imines as Conformationally Restrained 1,3-Diazabutadienes: Synthesis, Structural Properties and Protonation Reviewed

    Simon Janich, Roland Froehlich, Andrea Wilken, Jan von Zamory, Atsushi Wakamiya, Shigehiro Yamaguchi, Ernst-Ulrich Wuerthwein

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY   Vol. 2009 ( 13 ) page: 2077 - 2087   2009.5

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    5-Aryl-3,3,4,4-tetramethyl-3,4 -dihydro-3H-pyrrol-2-imines, conformationally restrained 1,3-diazabuta-1,3-diene derivatives, were, easily prepared by treating aryllithium species with 2,2,3,3-tetramthylsuccinonitrile (1). Trapping the reaction intermediate with chlorotrimethylsilane gave N-silylaled compounds 2a-e, whereas aqueous workup gave N-H derivatives 3a,b. Pyrenyl-substituted compound 3b was characterised by X-ray diffraction studies, revealing the presence of both intermolecular aromatic face-to-face contacts and the formation of homodimers by twotold H-bonding. N-Silylated derivatives 2a-d were used successfully as nucleophilic components in palladium-catalysed C-N bond-forming reactions to obtain N-arylated compounds 5b-h,j,k,m and 7a-d. The UV spectra of compounds 5 and 7 exhibit long wavelength absorptions up to 462 nm for 7d, thus indicating extended pi-pi* conjugation. Dihydropyrrolimine-based compounds with larger conjugated aryl substituents in the 5-position react. with Bronsted and Lewis acids displaying a significant colour change that could be used to estimate. the pK(1), of 3a to a value of -4.5. Derivatives 2c,e and 3a,b, which are not N-arylated, are fluorescent with a Stokes shift of 107 nm (6034 cm(-1)) for 3a. ((c) Wiley-VCH Verlag GmbH & Co, KGaA, 69451 Weinheim, Germany, 2009)

    DOI: 10.1002/ejoc.200900045

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  199. Electronic structure of bis(benzo)pentathienoacene in gas and solid phase: ultraviolet photoemission spectroscopy and energy band calculation

    Hiroyuki Yoshida, Yuji Watazu, Naoki Sato, Toshihiro Okamoto, Shigehiro Yamaguchi

    APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING   Vol. 95 ( 1 ) page: 185 - 191   2009.4

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    Ultraviolet photoemission spectroscopic measurements of bis (benzo)pentathienoacene were carried out in gas and solid phase. For the measurements of solid phase, vacuum deposited films in both amorphous and crystalline phase were prepared on different substrates of HOPG and polycrystalline Au, respectively. The adiabatic ionization energies were determined to be 6.8(4), 5.3(2), and 5.0(8) eV, for gas, amorphous, and crystalline phases, respectively. The spectral lineshapes were interpreted with the aid of the density functional calculations for both isolated molecule and single-crystal structure. The calculated electronic structures were further analyzed in terms of the energy band dispersion and the transport properties of charge carriers.

    DOI: 10.1007/s00339-008-5004-2

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  200. Coordination-Induced Intramolecular Double Cyclization: Synthesis of Boron-Bridged Dipyridylvinylenes and Dithiazolylvinylenes

    Qiang Zhao, Hongyu Zhang, Atsushi Wakamiya, Shigehiro Yamaguchi

    SYNTHESIS-STUTTGART   ( 1 ) page: 127 - 132   2009.1

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    Di(heteroaryl)acetylenes having a pyridyl or thiazolyl as the heteroaryl group underwent a reaction with bromodibenzoborole to produce coordination complexes, which were further treated with water to promote the intramolecular cascade double cyclization to produce the dibenzoborolyl-bridged ladder di(heteroaryl)vinylenes. For the thiazolyl derivative, further derivatization at the terminal positions produced a bis(dimesitylboryl)-substituted derivative. The ladder molecules prepared showed ail intense emission in the fluorescence spectra as well as reversible reduction waves at low reduction potentials in the cyclic voltammetry.

    DOI: 10.1055/s-0028-1083271

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  201. FT Raman and DFT Study on a Series of All-anti Oligothienoacenes End-Capped with Triisopropypsilyl Groups

    R. M. Osuna, V. Hern&aacute;ndez, J. T. L. Navarrete, J. Arag&oacute;, P. M. Viruela, E. Ort&iacute;, Y. Suzuki, S. Yamaguchi, J. T. Senssler, A. J. Matzger

    ChemPhysChem.   Vol. 10   page: 3069-3076   2009

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  202. Coordination-Induced Intramolecular Double Cyclization: Synthesis of Boron-Bridged Dipyridylvinylenes and Dithiazolylvinylenes

    Q. Zhao, H. Zhang, A. Wakamiya, and S. Yamaguchi

    Synthesis, 40th special issue     page: 127-132   2009

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  203. Electronic Structure of Bis(benzo)pentathienoacene in Gas and Solid Phase: Ultraviolet Photoemission Spectroscopy and Energy Band Calculation

    H. Yoshida, Y. Watazu, N. Sato, T. Okamoto, and S. Yamaguchi

    Appl. Phys. A   Vol. 95   page: 185-191   2009

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  204. *Intense Solid-State Blue Emission with a Small Stokes' Shift: pi-Stacking Protection of Diphenylanthracene Skeleton

    A. Iida and S. Yamaguchi

    Chem. Commun.     page: 3002-3004   2009

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  205. 5-Aryl-3,3,4,4-tetramethyl-3,4-dihydro-3H-pyrrol-2-imines

    S. Janich, R. Froehlich, A. Wilken, J. von Zamory, A. Wakamiya, S. Yamaguchi, and E.-U. Wuerthwein

    Eur. J. Org. Chem.     page: 2077-2087   2009

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  206. Structural Modification of Silicon-Bridged Ladder Stilbene Oligomers and Distyrylbenzenes

    H. Yamada, C. Xu, A. Fukazawa, A. Wakamiya, and S. Yamaguchi

    Macro. Chem. Phys.   Vol. 210   page: 904-916   2009

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  207. Long-Lived Exciplex Formation and Delayed Excition Emission in Bulk Heterojunction Blends of Silole Derivative and Polyfluorene Copolymer: The Role of Morphology on Exciplex Formation and Charge Separation

    J. J. Benson-Smith, J. Wilson, C. Dyer-Smith, K. Mouri, S. Yamaguchi, H. Murata, and J. Nelson

    J. Phys. Chem. B,   Vol. 113   page: 7794-7799   2009

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  208. Intramolecular Reductive Double Cyclization of o,o'-Bis(arylcarbonyl)diphenylacetylenes: Synthesis of Ladder π-Conjugated Skeletons

    H. Zhang, T. Karasawa, H. Yamada, A. Wakamiya, and S. Yamaguchi

    Org. Lett.   Vol. 11   page: 3076-3079   2009

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  209. Tetraaryl-tetradecahydroporphyrazins: Novel Porphyrin Derivatives Featuring a Cyclic Benzene Ring Tetramer

    S. Janich, R. Froehlich, A. Wakamiya, S. Yamaguchi, and E.-U. Wuerthwein

    Chem. Eur. J.   Vol. 15   page: 10457-10463   2009

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  210. Highly Emissive Diborylphenylene-Containing Bis(phenylethynyl)benzenes: Structure–Photophysical Property Correlations and Fluoride Ion Sen

    C.-H. Zhao, E. Sakuda, A. Wakamiya, and S. Yamaguchi

    Chem. Eur. J.   Vol. 15   page: 10603-10612   2009

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  211. *A B-B Bond-Containing Polycyclic π-Electron System: Dithieno-1,2-dihydro-1,2-diborin and Its Dianion Reviewed

    A. Wakamiya, K. Mori, T. Araki, and S. Yamaguchi

    J. Am. Chem. Soc.   Vol. 131   page: 10850-10851   2009

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  212. Ladder pi-Conjugated Materials Containing Main Group Elements

    A. Fukazawa, S. Yamaguchi

    Chem. Asian J.   Vol. 4   page: 1386-1400   2009

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  213. Oxidation of End-Capped Pentathienoacenes and Characterization of Their Radical Cations

    R. M. Osuna, M. C. R. Delgado, V. V. Hern&aacute;ndez, J. T. L. Navarrete, B. Vercelli, G. Zotti, J. J. Novoa, Y. Suzuki, S. Yamaguchi, J. T. Henssler, A. J. Matzger

    Chem. Eur. J   Vol. 15   page: 12346-12361   2009

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  214. Benzo[b]phosphole-Containing π-Electron Systems: Synthesis Based on an Intramolecular trans-Halophosphanylation and Some Insights into Their Properties

    A. Fukazawa, Y. Ichihashi, Y. Kosaka, and S. Yamaguchi

    Chem. Asian J.   Vol. 4   page: 1729-1740   2009

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  215. Regioselective Unsymmetrical Tetraallylation of C60 through Palladium Catalysis

    M. Nambo, A. Wakamiya, S. Yamaguchi, and K. Itami

    J. Am. Chem. Soc.   Vol. 131   page: 15112-15113   2009

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  216. Intense solid-state blue emission with a small Stokes' shift: pi-stacking protection of the diphenylanthracene skeleton

    Azusa Iida, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   ( 21 ) page: 3002 - 3004   2009

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    Intense blue emissions with a small Stokes' shift both in solution and in the solid state were attained by introducing (pentafluorophenyl) dimethylsilyl groups to a 9,10-diphenylanthracene skeleton as the pi-stacking tethers.

    DOI: 10.1039/b901794a

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  217. Benzo[b]phosphole-Containing pi-Electron Systems: Synthesis Based on an Intramolecular trans-Halophosphanylation and Some Insights into Their Properties

    Aiko Fukazawa, Yasunori Ichihashi, Youhei Kosaka, Shigehiro Yamaguchi

    CHEMISTRY-AN ASIAN JOURNAL   Vol. 4 ( 11 ) page: 1729 - 1740   2009

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    The intramolecular trans-halophosphanylation of 2-(aminophosphanyl)phenylacetylenes mediated by PBr3 followed by the oxidation with H2O2 produces 3-bromobenzo[b]phosphole oxide derivatives. This cyclization is also used for the synthesis of a 3-iodo derivative by conducting the reaction in the presence of LiI. Based on this synthetic method, various benzophosphole-containing pi-conjugated compounds, including a phosphoryl and methylene-bridged stilbene 10, 2,3,6,7-tetraphenylbenzo[1,2-b:4,5-b']diphosphole-P,P'-dioxides 11, and their phosphine sulfide derivatives 12, are synthesized. The study of the structure-property relationships in a series of the bridged stilbenes, including a bis(methylene)-bridged stilbene 10, and a bis-(phosphoryl)-bridged stilbene, reveals that as the contribution of the phosphoryl groups increased, the absorption and emission maxima substantially shift to longer wavelengths. The intrinsic substituent effects of the phosphoryl group in this skeleton are to decrease the oscillator strength of the electronic transition and thus decrease the radiative decay rate constants from the singlet excited state. Nevertheless, these compounds maintain high fluorescence quantum yields (Phi(F) > 0.8) owing to the significantly retarded non-radiative decay process. In the study of the benzodiphosphole derivatives 11 and 12, their cyclic voltammetry revealed that both of the phosphoryl and phosphine sulfide derivatives have low reduction potentials (-1.7 to -1.8 V vs ferrocene/ferrocenium couple) with the high reversibility of the redox waves. These compounds also showed high thermal stabilities with the high glass transition temperatures of 147-159 degrees C, indicative of their potential utilities as amorphous materials.

    DOI: 10.1002/asia.200900303

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  218. 5-Aryl-3,3,4,4-tetramethyl-3,4-dihydro-3H-pyrrol-2-imines

    S. Janich, R. Froehlich, A. Wilken, J. von Zamory, A. Wakamiya, S. Yamaguchi, E.-U. Wuerthwein

    Eur. J. Org. Chem.     page: 2077-2087   2009

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  219. Highly Emissive Diborylphenylene-Containing Bis(phenylethynyl)benzenes: Structure-Photophysical Property Correlations and Fluoride Ion Sensing

    Cui-Hua Zhao, Eri Sakuda, Atsushi Wakamiya, Shigehiro Yamaguchi

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 15 ( 40 ) page: 10603 - 10612   2009

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    A series of 2,5-bis(dimesitylboryl)-1,4-bis(arylethynyl)benzenes 1-6 that contain various p-substituents on the terminal benzene rings, including NPh2 (1), OMe (2), Me (3), H (4), CF3 (5), and CN (6) groups, were synthesized, and the effects of the p-substituents on the absorption and fluorescence properties were investigated both in solution and in the solid state. Linear relationships were obtained not only between the Hammett sigma(+)(p) constants of the p-substituents and the absorption and fluorescence maxima, quantum yields, and excited-state dynamics parameters in solution, but also between the sigma(+)(p) constants and the fluorescence quantum yields in the solid state. An important finding extracted from these results is that the suppressed fluorescence quenching in the solid state is a common feature for the present laterally boryl-substituted pi-conjugated skeletons. Hence, the diborylphenylene can serve as a useful core unit to develop highly emissive organic solids. In fact, most of the derivatives showed more intense emission in the solid state than in solution. In addition to these studies, the titration experiment of 1 by the addition of nBu(4)NF was conducted, which showed the stepwise bindings of two fluoride ions with high association constants as well as a drastic change in the fluorescence spectra, while constantly maintaining high quantum yields (0.61-0.76), irrespective of the binding modes. This result also demonstrated the potential utility of the present molecules as an efficient fluorescent fluoride ion sensor.

    DOI: 10.1002/chem.200900864

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  220. Tetraaryl Tetradecahydroporphyrazins: Novel Porphyrin Derivatives Featuring a Cyclic Benzene-Ring Tetramer

    Simon Janich, Roland Froehlich, Atsushi Wakamiya, Shigehiro Yamaguchi, Ernst-Ulrich Wuerthwein

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 15 ( 40 ) page: 10457 - 10463   2009

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    Treatment of tetramethylsuccinonitrile 1 with aryl lithium compounds and subsequent quenching with chlorotrimethylsilane yields 5-aryl-3,3,4,4-tetramethyl-N-(trimethylsilyl)-3,4-dihydropyrrol-2-imines 2a-c in 49-71% yield. Attempts to crystallise 2a-c in the presence of wet air yielded the tetraaryl tetradecahydroporphyrazins 3a-c in yields of 4-84% as single diastereomers. X-ray diffraction studies of 3b and c showed that only the isomer with four aryl substituents pointing in the same direction was formed. The resulting four-bladed pinwheel-like structures were characterised by four intramolecular aromatic interactions, in which each phenyl ring points with its edge towards the centre of a neighbouring phenyl moiety, resembling the arrangement of benzene molecules in T-shaped dimers. Temperature-dependent NMR spectra give insight into the dynamic properties of the aryl substituents. Quantum chemical calculations that included dispersion corrections indicated the importance of aryl-aryl interactions for the diastereoselectivity of the reaction and for the structural properties of the single isomers observed.

    DOI: 10.1002/chem.200901187

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  221. Regioselective Unsymmetrical Tetraallylation of C60 through Palladium Catalysis

    M. Nambo, A. Wakamiya, S. Yamaguchi, K. Itami

    J. Am. Chem. Soc.   Vol. 131   page: 15112-15113   2009

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  222. Oxidation of End-Capped Pentathienoacenes and Characterization of Their Radical Cations

    Reyes Malave Osuna, M. Carmen Ruiz Delgado, Victor Hernandez, Juan T. Lopez Navarrete, Barbara Vercelli, Gianni Zotti, Juan J. Novoa, Yoshitake Suzuki, Shigehiro Yamaguchi, John T. Henssler, Adam J. Matzger

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 15 ( 45 ) page: 12346 - 12361   2009

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    A detailed investigation of the optical and electrochemical properties of two pentathienoacene derivatives, 2,6-bis(trimethylsilyl)-alpha-pentathienoacene (TMS-T5-TMS) and 2,6-bis(triisopropylsilyl)-alpha-pentathienoacene (TIPS-T5-TIPS), as the neutral and oxidized species was performed in the temperature range of 80-300 K. The experimental solution UV/Vis and solid-state Raman spectra were interpreted by using time-dependent DFT and DFT quantum chemical calculations at the B3LYP/6-31G** level. Bond lengths, HOMO-LUMO positions, and charge distribution were also predicted by computational methods for both the neutral and oxidized states of each thienoacene. As evidenced by ESR and spectroelectrochemical data, upon oxidation the pentathienoacene derivative with the less sterically hindering trimethylsilyl solubilizing groups, TMS-T5-TMS, undergoes pi dimerization to form [TMS-T5-TMS](2)(2+). In contrast, TIPS-T5-TIPS, with the more bulky triisopropylsilyl solubilizing groups, was oxidized to the radical cation but dimerization was prevented due to steric interactions. These experimental observations are supported by DFT calculations, which were used to investigate [TMS-T5-TMS](2)(2+) and [TIPS-T5-TIPS](2)(2+) pi dimers in the solid state and in solution. The redox potentials and absorption peak locations corresponding to the radical cations and pi dimer of TMS-T5-TMS were identified experimentally.

    DOI: 10.1002/chem.200900246

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  223. Ladder pi-Conjugated Materials Containing Main-Group Elements

    Aiko Fukazawa, Shigehiro Yamaguchi

    CHEMISTRY-AN ASIAN JOURNAL   Vol. 4 ( 9 ) page: 1386 - 1400   2009

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    Ladder pi-conjugated compounds, which have fully ring-fused polycyclic skeletons, are an important class of materials possessing significant potentials for application in organic electronics. The incorporation of main-group elements, such as B, Si P, S, and Se, into the ladder skeletons as bridging moieties is a powerful strategy to endow unusual electronic structures as well as suitable molecular arrangements in the solid state, giving rise to attractive photophysical and electronic properties. Recent efforts have produced a number of fascinating ladder materials, some of which indeed showed high performance as light-emitting materials and charge carrier transporting materials. This Focus Review is an overview of the progress in this chemistry, focusing on several important pi-conjugated skeletons.

    DOI: 10.1002/asia.200900179

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  224. Synthesis and Electronic Spectra of Disilatriptycene Oligomers: Evidence for Electronic Delocalization along the One-Dimensional Arrangement of Bridge-Head Disilanes

    Shohei Sase, Yoen-Seok Cho, Atsushi Kawachi, Atsushi Wakamiya, Shigehiro Yamaguchi, Hayato Tsuji, Kohei Tamao

    ORGANOMETALLICS   Vol. 27 ( 21 ) page: 5441 - 5445   2008.11

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    Reductive coupling of a 9,10-dibromo-9,10-disilatriptycene derivative followed by treatment with chlorotrimethylsilane (TMSCI) affords a series of TMS-capped 9, 10-disilatriptycene oligomers DSiT[n]. Each isomer, up to the pentamer (n = 5), can be separated using recycling gel permeation chromatography. The X-ray structural analysis of DSiT[2] shows that the six silicon atoms are linearly aligned in a rigid array structure. While the ultraviolet (UV) absorption maximum remains constant at 230 nm, irrespective of the chain length, the magnetic circular dichroism (MCD) spectra exhibit a red shift band near 245 nm, and the emission maximum steadily shifts from 319 to 337 nm as the number of silicon atom increases. These spectra indicate the occurrence of electronic delocalization along the one-dimensional arrangement of bridge-head disilane moieties.

    DOI: 10.1021/om701283e

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  225. Red-emissive Polyphenylated BODIPY Derivatives: Effect of Peripheral Phenyl Groups on the Photophysical and Electrochemical Properties

    Atsushi Wakamiya, Naoya Sugita, Shigehiro Yamaguchi

    CHEMISTRY LETTERS   Vol. 37 ( 10 ) page: 1094 - 1095   2008.10

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    A series of red-emissive BODIPY derivatives 2-4 having five to seven phenyl groups on their periphery were synthesized., and their photophysical and electrochemical properties were investigated. While the 8-phenyl-substituted derivatives only have moderate fluorescence quantum yields in solution, they can show intense red fluorescence in the PMMA films. The peripheral phenyl groups also affect the redox reversibility in cyclic voltammetry.

    DOI: 10.1246/cl.2008.1094

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  226. Design and synthesis of boron-containing functional pi-electron materials

    Atsushi Wakamiya, Shigehiro Yamaguchi

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   Vol. 66 ( 9 ) page: 858 - 868   2008.9

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    Utilization of boron, a group 13 element, as a key element for developing new functional electronic and optoelectronic materials is an important direction in the organoboron chemistry. Boron has several characteristic features, such as trigonal planar geometry for trivalent boron compounds, high Lewis acidity, and effective orbital interaction with pi-conjugated frameworks through the vacant p-orbital (i.e., p(pi)-pi* conjugation). Exploiting these features of the boron element for molecular designs allows us to create sophisticated pi-electron materials having attractive photophysical and electronic properties. We here present some progress in our chemistry, including B,B',B"-trianthrylborazine (B3N3)-based molecular bundles, boryl-substituted thienylthiazole pi-electron systems with intramolecular B-N coordination, borole- and dibenzoborole-based pi-conjugated compounds, and boryl-substituted emissive organic solids.

    DOI: 10.5059/yukigoseikyokaishi.66.858

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  227. Electronic modulation of fused oliglothiophenes by chemical oxidation

    Yoshitake Suzuki, Toshihiro Okamoto, Atsushi Wakamiya, Shigehiro Yamaguchi

    ORGANIC LETTERS   Vol. 10 ( 16 ) page: 3393 - 3396   2008.8

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    The reaction of pentathienoacene (f-5T) with mCPBA produced a series of oxidized derivatives containing one or two thiophene-S,S-dioxide rings. The regioselectivity of the oxidation reflects the aromaticity of each thiophene ring in the f-5T skeleton, and the extent of the oxidation significantly affects the fluorescence and redox properties.

    DOI: 10.1021/ol801136k

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  228. Highly electron-donating 3,3 '-diaryl-1,1 '-bi(isobenzofuran)s synthesized by photochemical exocyclic [2+2+2] cycloaddition

    Hongyu Zhang, Atsushi Wakamiya, Shigehiro Yamaguchi

    ORGANIC LETTERS   Vol. 10 ( 16 ) page: 3591 - 3594   2008.8

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    Facile photochemical exocyclic [2 + 2 + 2] cycloaddition produced a series of electron-donating 1,1'-bi(isobenzofuran)s having various aryl groups at the 3,3' positions. The 1,1'-bi(isobenzofuran) skeleton with a highly coplanar structure is a useful building unit to construct the narrow bandgap pi-conjugated systems with low oxidation potentials.

    DOI: 10.1021/ol801358c

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  229. Synthesis and structural characterization of pentaarylboroles and their dianions

    Chcuk-Wai So, Daisuke Watanabe, Atsushi Wakamiya, Shigehiro Yamaguchi

    ORGANOMETALLICS   Vol. 27 ( 14 ) page: 3496 - 3501   2008.7

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    A series of l-aryl-2,3,4,5-tetraphenylboroles [Ph(4)C(4)BAr] [Ar = p-MeC(6)H(4) (2), p-Me(3)SiC(6)H(4)(3), p-FC(6)H(4) (4)] were synthesized. The X-ray crystallography of 2-4 revealed that they have short distances between the borole boron atom and the phenyl rings of the neighboring molecules, suggesting the existence of certain intermolecular interaction. Despite this interaction, the borole rings in 2-4 remain planar and contain substantial bond alternation in the butadiene skeleton, which is consistent with the theoretically optimized structures of the singlet boroles. These results demonstrated that the boroles still have antiaromatic character in the crystalline state. Compound 3 and pentaphenylborole [Ph(4)C(4)BPh] (5) were further reacted with potassium or potassium graphite to form potassium borole dianion salts [K(2){Ph(4)C(4)B(p-Me(3)SiC(6)H(4)))] (6) and [K(2){Ph(4)C(4)BPh)] (7), respectively. In their X-ray crystal structures, compounds 6 and 7 are polymeric and have two K(+) ions lying on both sides of the borole plane With eta(5)-coordination.

    DOI: 10.1021/om8002812

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  230. Bis-phosphoryl-bridged stilbenes synthesized by an intramolecular cascade cyclization

    Aiko Fukazawa, Masanao Hara, Toshihiro Okamoto, Eun-Cheol Son, Caihong Xu, Kohei Tamao, Shigehiro Yamaguchi

    ORGANIC LETTERS   Vol. 10 ( 5 ) page: 913 - 916   2008.3

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    Bis-phosphoryl-bridged stilbenes have been synthesized using an intramolecular cascade cyclization. They show intense blue fluorescences at longer wavelengths with higher quantum yields compared to those of the known element-bridged stilbenes. In addition, they have much lower reduction potentials due to the inductive effect of phosphoryl groups. The incorporation of the phosphoryl moiety is an effective way for the construction of highly electron-accepting pi-conjugated systems.

    DOI: 10.1021/ol7030608

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  231. Synthesis and Electronic Spectra of Disilatriptycene Oligomers: Evidence for Electronic Delocalization along the One-Dimensional Arrangement of Bridge-Head Disilanes

    S. Sase, Y.-S. Cho, A. Kawachi, A. Wakamiya, S. Yamaguchi, H. Tsuji, and K. Tamao

    Organometallics   Vol. 27   page: 5441-5445   2008

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  232. *Phosphonium and Borate-Bridged Zwitterionic Ladder Stilbene and Its Extended Analogues Reviewed

    A. Fukazawa, H. Yamada, and S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 47   page: 5582-5585   2008

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  233. Kinetically Stabilized Dibenzoborole as an Electron-Accepting Building Unit

    A. Wakamiya, K. Mishima, K. Ekawa, and S. Yamaguchi

    Chem. Commun.,     page: 579-581   2008

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  234. Bis-Phosphoryl-Bridged Stilbenes Synthesized by an Intramolecular Cascade Cyclization

    A. Fukazawa, M. Hara, T. Okamoto. E.-C. Son, C. Xu, K. Tamao, and S. Yamaguchi

    Org. Lett.   Vol. 10   page: 913-916   2008

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  235. Synthesis and Structural Characterization of Pentaarylboroles and Their Dianions

    C.-W. So, D. Watanabe, A. Wakamiya, and S. Yamaguchi

    Organometallics   Vol. 27   page: 3496-3501   2008

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  236. Disilylphenylene and Tetrasilylphenylene as a New Building Unit for Highly Fluorescent Poly(aryleneethynylene)s

    A. Iida, K. Nagura, and S. Yamaguchi

    Chem. Asian J.   Vol. 3   page: 1456-1464   2008

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  237. Electronic Modulation of Fused Oligothiophenes by Chemical Oxidation

    Y. Suzuki, T. Okamoto, A. Wakamiya, and S. Yamaguchi

    Org. Lett.   Vol. 10   page: 3393-3396   2008

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  238. Highly Electron-Donating 3,3'-Diaryl-1,1'-Bi(isobenzofuran)s Synthesized by Photochemical Exocyclic [2+2+2] Cycloaddition

    H. Zhang, A. Wakamiya, and S. Yamaguchi

    Org. Lett.   Vol. 10   page: 3591-3594   2008

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  239. Design and Synthesis of Boron-Containing Functional pi-Electron Materials

    A. Wakamiya, and S. Yamaguchi

    J.Syn. Org. Chem., Jpn.   Vol. 66   page: 858-868   2008

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  240. Red-Emissive Polyphenylated BODIPY Derivatives: Effect of Peripheral Phenyl Groups on the Photophysical and Electrochemical Properties

    A. Wakamiya, N. Sugita, and S. Yamaguchi

    Chem. Lett.   Vol. 37   page: 1094-1095   2008

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  241. Phosphonium- and borate-bridged zwitterionic ladder stilbene and its extended analogues Reviewed

    Aiko Fukazawa, Hiroshi Yamada, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 47 ( 30 ) page: 5582 - 5585   2008

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    DOI: 10.1002/anie.200801834

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  242. Disilylphenylene and tetrasilylphenylene as new building unit for highly fluorescent poly(aryleneethynylene)s

    Azusa Iida, Kazuhiko Nagura, Shigehiro Yamaguchi

    CHEMISTRY-AN ASIAN JOURNAL   Vol. 3 ( 8-9 ) page: 1456 - 1464   2008

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    We report the synthesis and photophysical properties of poly(aryleneethynylene)s (PAEs) containing disilyl- or tetrasilyl-substituted phenylene as the key building unit. The fluorescence spectra of one of the PAEs, consisting of the diethynylbis(trimethylsilyl)phenylene and fluorenylene units, shows an intense blue emission with the maximum at 428 nm. The absolute quantum yield (0,) and the fluorescence lifetime (Phi(F)) are 0.92 and 0.39 ns, respectively. The calculated radiative decay rate constant (k(r)) from the singlet excited state, based on Phi(F) and tau(s), is 2.4 x 10(9) s(-1), which is extremely large for organic molecules. A series of silyl-substituted PAEs, including a tricyclic tetrasilylphenylene-containing polymer, also show intense emissions with large k(r) values. Theoretical calculations of the model systems with the bis(phenylethynyl)benzene skeleton reveal the general substituent effect of the silyl groups attached to the PAE skeleton.

    DOI: 10.1002/asia.200800125

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  243. 2,5-Thienylene-bridged triangular and linear porphyrin trimers Reviewed

    J. Song, S.Y. Jang, S. Yamaguchi, J. Sankar, S. Hiroto, N. Aratani, J.-Y. Shin, S. Easwaramoorthi, K.S. Kim, D. Kim, H. Shinokubo, A. Osuka

    Angewandte Chemie - International Edition   Vol. 47 ( 32 ) page: 6004 - 6007   2008

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  244. Kinetically stabilized dibenzoborole as an electron-accepting building unit

    Atsushi Wakamiya, Kotaro Mishima, Kanako Ekawa, Shigehiro Yamaguchi

    CHEMICAL COMMUNICATIONS   ( 5 ) page: 579 - 581   2008

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    A synthetic route to a dibenzoborole, kinetically stabilized by the 2,4,6-tri-tert-butylphenyl group, was developed, and a series of pi-extended derivatives were synthesized, which show orange-red emissions and stable electrochemical redox properties.

    DOI: 10.1039/b716107g

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  245. Coplanar oligo(p-phenylenedisilenylene)s based on the octaethyl-substituted s-hydrindacenyl groups Reviewed

    Aiko Fukazawa, Yongming Li, Shigehiro Yamaguchi, Hayato Tsuji, Kohei Tamao

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 129 ( 46 ) page: 14164 - +   2007.11

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    The silicon analogues of the oligo(p -phenylenevinylene)s (Si-OPVs) with highly planar structures have been synthesized using a newly developed ligand, the 1,1,3,3,5,5,7,7-octaethyl-s -hydrindacen-4-yl (Eind) group. Their X-ray crystal structures and spectroscopic data demonstrate that the pi-conjugation effectively extends over the Si-OPV framework. Notably, tetrasiladistyrylbenzene exhibits an orange fluorescence even at room temperature both in solution and in the solid state, which is attributable to the effective extension of conjugation. To the best of our knowledge, the tetrasiladistyrylbenzene is the first emissive Si=Si derivative even at room temperature.

    DOI: 10.1021/ja0764207

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  246. Thiophene- and selenophene-based heteroacenes: Combined quantum chemical DFT and spectroscopic Raman and UV-vis-NIR study

    Reyes Malave Osuna, Rocio Ponce Ortiz, Toshihiro Okamoto, Yoshitake Suzuki, Shigehiro Yamaguchi, Victor Hernandez, Juan Teodomiro Lopez Navarrete

    JOURNAL OF PHYSICAL CHEMISTRY B   Vol. 111 ( 26 ) page: 7488 - 7496   2007.7

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    In this article, we report the characterization of a series of thiophene- and selenophene-based heteroacenes, materials with potential applications in organic electronics. In contrast to the usual alpha-oligothiophenes, these annelated oligomers have a larger band gap than most semiconductors currently used in the fabrication of organic field-effect transistors (OFETs) and therefore they are expected to be more stable in air. The synthesis of these fused-ring molecular materials was motivated by the notion that a more rigid and planar structure should reduce defects (such as torsion about single bonds between alpha-linked units or S-syn defects) and thus improve pi-conjugation for better charge-carrier mobility. The conjugational properties of these heteroacenes have been investigated by means of FT-Raman spectroscopy, revealing that pi-conjugation increases with the increasing number of annelated rings. DFT and TDDFT quantum chemical calculations have been performed, at the B3LYP/6-31G** level, to assess information regarding the minimum-energy molecular structure, topologies, and absolute energies of the frontier molecular orbitals around the gap, vibrational normal modes related to the main Raman features, and vertical one-electron excitations giving rise to the main optical absorptions.

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  247. Energy migration in conjugated polymers: the role of molecular structure

    Aimee Rose, John D. Tovar, Shigehiro Yamaguchi, Evgueni E. Nesterov, Zhengguo Zhu, Timothy M. Swager

    PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES   Vol. 365 ( 1855 ) page: 1589 - 1606   2007.6

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    Conjugated polymers undergo facile exciton diffusion. Different molecular structures were examined to study the role of the excited state lifetimes and molecular conformations on energy transfer. There is a clear indication that extended fluorescence lifetimes give enhanced exciton diffusion as determined by fluorescence depolarization measurements. These results are consistent with a strong electronic coupling or Dexter-type energy transfer as the dominating mechanism. The control of polymer conformations in liquid crystal solvents was also examined and it was determined that more planar conformations gave enhanced energy transfer to emissive low band-gap endgroups.

    DOI: 10.1098/rsta.2007.2033

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  248. Highly emissive poly(aryleneethynylene)s containing 2,5-diboryl-1,4-phenylene as a building unit

    Cui-Hua Zhao, Atsushi Wakamiya, Shigehiro Yamaguchi

    MACROMOLECULES   Vol. 40 ( 11 ) page: 3898 - 3900   2007.5

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    DOI: 10.1021/ma0702997

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  249. Single-crystal field-effect transistors of benzoannulated fused oligothiophenes and oligoselenophenes

    Koichi Yamada, Toshihiro Okamoto, Kenichi Kudoh, Atsushi Wakamiya, Shigehiro Yamaguchi, J. Takeya

    APPLIED PHYSICS LETTERS   Vol. 90 ( 7 ) page: 072102   2007.2

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    Recently synthesized benzoannulated fused oligothiophenes and oligoselenophenes are introduced as air-stable organic semiconductors for high-performance organic field-effect transistors. To evaluate electronic mobility intrinsic to the materials, the technique of single-crystal transistors is employed for two representative compounds of benzoannulated pentathienoacene f-B5TB and its selenium analog f-BT3STB. High mobility of approximately 1.1 cm(2)/V s is achieved for the selenium compound due to its considerable Se---Se orbital interactions. The materials simultaneously bear features of high mobility and high duration in ambient atmosphere. (c) 2007 American Institute of Physics.

    DOI: 10.1063/1.2535617

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  250. Ladder distyrylbenzenes with silicon and chalcogen bridges: Synthesis, structures, and properties

    Kazuhiro Mouri, Atsushi Wakamiya, Hiroshi Yamada, Takashi Kajiwara, Shigehiro Yamaguchi

    ORGANIC LETTERS   Vol. 9 ( 1 ) page: 93 - 96   2007.1

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    A cascade-type anionic double cyclization of (o-silylphenyl)(o-halophenyl)acetylenes via lithiation followed by treatment with elemental chalcogen produces silicon and chalcogen-bridged stilbenes. Based on this reaction, a series of silicon and sulfur- or silicon and selenium-bridged ladder distyrylbenzenes have been synthesized. Their chemical modification by oxidation, crystal structures, and photophysical properties are described.

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  251. Ladder Distyrylbenzenes with Silicon and Chalcogen Bridges: Synthesis, Structures, and Properties

    K. Mouri, A. Wakamiya, H. Yamada, T. Kajiwara, and S. Yamaguchi

    Org. Lett.   Vol. 9   page: 93-96   2007

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  252. General Synthesis of Extended Fused Oligothiophenes Consisting of Even Number of Thiophene Rings

    T. Okamoto, K. Kudoh, A. Wakamiya, and S. Yamaguchi

    Chem. Eur. J.   Vol. 13   page: 548-556   2007

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  253. Thiophene and Selenophene-Based Heteroacenes: Combined Quantum Chemical DFT, and Spectroscopic Raman and UV-Vis-NIR Study

    R. M. Osuna, R. P. Ortiz, T. Okamoto, Y. Suzuki, S. Yamaguchi, V. Hernandez, J. Teodomiro, and L. Navarrete

    J. Phys. Chem. B   Vol. 111   page: 7488-7496   2007

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  254. Highly Emissive Poly(aryleneethynylene)s Containing 2,5-Dibroyl-1,4-Phenylene as a Building Unit

    C. -H. Zhao, A. Wakamiya, and S. Yamaguchi

    Macromolecules   Vol. 40   page: 3898-3900   2007

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  255. *3-Boryl-2,2'-Bithiophene as a Versatile Core Skeleton for Full-Color Highly Emissive Organic Solids

    A. Wakamiya, K. Mori, and S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 46   page: 4273-4276   2007

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  256. *Single Crystal Field Effect Transistors of Benzo-Annulated Fused Oligothiophenes and Oligoselenophenes

    K. Yamada, T. Okamoto, K. Kudoh, A. Wakamiya, S. Yamaguchi, and J. Takeya

    Appl. Phys. Lett.   Vol. 90   page: 072102   2007

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  257. Crystallographic and Chiroptical Studies on Tetraarylferrocenes for Use as Chiral Rotary Modules for Molecular Machines

    T. Muraoka, K. Kinbara, A. Wakamiya, S. Yamaguchi, and T. Aida

    Chem. Eur. J.   Vol. 13   page: 1724-1730   2007

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  258. 3-Boryl-2,2 '-bithiophene as a versatile core skeleton for full-color highly emissive organic solids

    Atsushi Wakamiya, Kenji Mori, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 46 ( 23 ) page: 4273 - 4276   2007

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    DOI: 10.1002/anie.200604935

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  259. Crystallographic and Chiroptical Studies on Tetraarylferrocenes for Use as Chiral Rotary Modules for Molecular Machines

    T. Muraoka, K. Kinbara, A. Wakamiya, S. Yamaguchi, T. Aida

    Chem. Eur. J.   Vol. 13   page: 1724-1730   2007

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  260. Field effect transistors of single crystal benzo-annulated fused oligothiophenes and oligoselenophenes Reviewed

    Y. Tominari, K. Yamada, M. Yamagishi, Jun Takeya, T. Okamoto, K. Kudoh, A. Wakamiya, S. Yamaguchi

    Materials Research Society Symposium Proceedings   Vol. 1003   page: 112 - 117   2007

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    Recently synthesized benzo-annulated fused oligothiophenes and oligoselenophenes are introduced as air-stable organic semiconductors for high-performance organic field-effect transistors. To evaluate electronic mobility intrinsic to the materials, single-crystal transistors are prepared for two representative compounds of benzo-annulated pentathienoacene f-B5TB and its selenium analogue f-BT3STB. High mobility of more than 1 cm2/Vs is achieved for the selenium compound, due to its considerable Se- - -Se orbital interactions. The transistor performances have been stable for two months, indicating high duration of the compound in the ambient atmosphere. Copyright © 2007 Materials Research Society.

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  261. General synthesis of extended fused oligothiophenes consisting of an even number of thiophene rings

    Toshihiro Okamoto, Kenichi Kudoh, Atsushi Wakamiya, Shigehiro Yamaguchi

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 13 ( 2 ) page: 548 - 556   2007

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    The intramolecular double cyclization of bis(3-bromo-2-thienyl)acetylenes though a lithium-halogen exchange reaction with tBuLi followed by treatment with elemental sulfur produces two thiophene-fused thieno[3,2-c](1,2-dithiin)s. The subsequent dechal-cogenation from the 1,2-dithiins with copper nanopowder affords tetrathienoacenes. On the basis of this two-step procedure, a series of trialkylsilyl-terminated, fused oligothiophenes, including hexathienoacene (a six thiophene-fused system) and octathienoacene (an eight thiophene-fused system), were synthesized. In the UV/Vis absorption and fluorescence spectra of the fused oligothiophenes, the absorption and emission maxima shift to longer wavelengths, as the pi-conjugation length increases. Their maximum wavenumbers have linear relationships with the reciprocal number of thiophene rings consisting of the it-conjugated frameworks. In the cyclic voltammograms, all the compounds show reversible oxidation waves, the first oxidation potential of which shifts to less positive as the conjugation length increases. Among them, the octathienoacene also shows a reversible second oxidation process. Indeed, its chemical oxidation with an excess amount of NO+SbF6- produces the dication as a golden crystal. The crystal structures of the neutral octathienoacene and its dication were determined by X-ray crystallography. While in the neutral state, the octathienoacene has a benzenoid structure with a large bond alternation of about 0.04 angstrom, its dication has a quinoid structure in which two cationic charges are mainly localized on the terminal rings.

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  262. Highly emissive organic solids containing 2,5-diboryl-1,4-phenylene unit

    Cui-Hua Zhao, Atsushi Wakamiya, Yuko Inukai, Shigehiro Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 128 ( 50 ) page: 15934 - 15935   2006.12

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    DOI: 10.1021/ja0637550

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  263. High fidelity self-sorting assembling of meso-cinchomeronimide appended meso-meso linked Zn(II) diporphyrins

    Taisuke Kamada, Naoki Aratani, Toshiaki Ikeda, Naoki Shibata, Yoshiki Higuchi, Atsushi Wakamiya, Shigehiro Yamaguchi, Kil Suk Kim, Zin Seok Yoon, Dongho Kim, Atsuhiro Osuka

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 128 ( 23 ) page: 7670 - 7678   2006.6

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    In noncoordinating solvents, meso-cinchomeronimide appended Zn(II) porphyrin 2 forms a cyclic trimer, while diporphyrins 7 exhibit high-fidelity self-sorting assembling to form discrete cyclic trimer, tetramer, and pentamer with large association constants from 7(in-in), 7(in-out), and 7(out-out), respectively, through almost perfect discrimination of enantiomeric and conformational differences of the meso-cinchomeronimide substituents. In the latter self-sorting processes, the dihedral angles dictated by the two pyridyl nitrogen atoms control the size of the aggregates; the trimer from 7(in-in), the tetarmer from 7(in-out), and the pentamer from 7(out-out). Cyclic structures of (2) 3 and (R-7(out-out)) 5 have been determined by single-crystal X-ray diffraction analysis.

    DOI: 10.1021/ja0611137

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  264. Reactions of fused polycyclic 1,2-dithiins with transition metals: Synthesis of heteroacenes via desulfurization

    K Kudoh, T Okamoto, S Yamaguchi

    ORGANOMETALLICS   Vol. 25 ( 9 ) page: 2374 - 2377   2006.4

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    Bis(thieno[3,2-b]thiophene)-fused 1,2-dithiin reacts with a stoichiometric amount of Ni(cod)(2)/2PPh(3) to produce a dimeric Ni(II) complex via the oxidative addition of the disulfide bond in the 1,2-dithiin skeleton to the Ni(0) center. An X-ray crystal structure analysis revealed that this complex has a dimeric structure in which one sulfur atom derived from the disulfide bond bridges two metal centers. The resultant Ni complex undergoes desulfurization at elevated temperature to produce a fully fused thiophene-based heteroacene.

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  265. Ladder pi-conjugated materials with main group elements

    S Yamaguchi, CH Xu, T Okamoto

    PURE AND APPLIED CHEMISTRY   Vol. 78 ( 4 ) page: 721 - 730   2006.4

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    Ladder-type pi-conjugated skeletons are promising building units for new materials for organic electronics, wherein their annelated coplanar structures enhance the pi-conjugation, leading to a set of desirable properties such as intense fluorescence and high carrier mobility. As a new entry into this class of skeletons, we now disclose two series of ladder molecules, i.e., silicon- and carbon-bridged oligo(p-phenylenevinylene)s and thiophene- and selenophene-based heteroacenes. The former ladder molecules contain the silole substructure in which the silicon bridges affect the electronic structure and thus photophysical properties through the sigma*-pi* conjugation. The latter heteroacenes can be recognized as the heteroatom analogs of acenes and may be promising materials for organic thin film transistors. These two series of molecules have been synthesized based on newly developed intramolecular cyclizations of acetylenic compounds.

    DOI: 10.1351/pac200678040721

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  266. Highly Fidelity Self-Sorting Assembling of meso-Cinchomeronimide Appended meso-meso Linked Zn(II) Diporphyrins

    T. Kamada, N. Aratani, T. Ikeda, N. Shibata, Y. Higuchi, A. Wakamiya, S. Yamaguchi, K. S. Kim, Z. S. Yoon, D. Kim, A. Osuka

    J. Am. Chem. Soc.   Vol. 128   page: 7670-7678   2006

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  267. Reactions of Fused Polycyclic 1,2-Dithiins with Transiton Metals: Synthesis of Heteroacenes via Desulfurization

    K. Kudoh, T. Okamoto, and S. Yamaguchi

    Organometallics   Vol. 25   page: 2374-2377   2006

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  268. Boron as a Key Component for New pi Electron Materials

    S. Yamaguchi and A. Wakamiya

    Pure Appl. Chem.   Vol. 78   page: 1413-1424   2006

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  269. Ladder pi-Conjugated Materials with Main Group Elements

    S. Yamaguchi, C. Xu, and T. Okamoto

    Pure Appl. Chem.   Vol. 78   page: 721-730   2006

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  270. Highly Emissive Organic Solids Containing 2,5-Diboryl-1,4-Phenylene Unit

    C. -H. Zhao, A. Wakamiya, Y. Inukai, and S. Yamaguchi

    J. Am. Chem. Soc.   Vol. 128   page: 15934-15935   2006

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  271. Intramolecular B-N Coordination as a New Scaffold for Design of Electron Transporting Materials: Synthesis and Properties of Boryl-Substituted Thienylthiazoles

    A. Wakamiya, T. Taniguchi, and S. Yamaguchi

    Angew. Chem. Int. Ed.   Vol. 45   page: 3170-3173   2006

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  272. Boron as a Key Component for New pi Electron Materials

    S. Yamaguchi, A. Wakamiya

    Pure Appl. Chem.   Vol. 78   page: 1413-1424   2006

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  273. Intramolecular B-N coordination as a scaffold for electron-transporting materials: Synthesis and properties of boryl-substituted thienylthiazoles

    Atsushi Wakamiya, Takuhiro Taniguchi, Shigehiro Yamaguchi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 45 ( 19 ) page: 3170 - 3173   2006

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    DOI: 10.1002/anie.200504391

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  274. Synthesis and photophysical properties of new π-electron systems containing boryl groups at the side positions Reviewed

    A. Wakamiya, C.-H. Zhao, K. Mori, S. Yamaguchi

    Polymer Preprints, Japan   Vol. 55 ( 2 ) page: 3023 - 3024   2006

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  275. Synthesis, structures, and photophysical properties of silicon and carbon-bridged ladder oligo(p-phenylenevinylene)s and related pi-electron systems

    S Yamaguchi, CH Xu, H Yamada, A Wakamiya

    JOURNAL OF ORGANOMETALLIC CHEMISTRY   Vol. 690 ( 23 ) page: 5365 - 5377   2005.11

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    A series of partially or fully fused ladder oligo(p-phenylenevinylene)s (LOPVs) and related pi-electron systems has been synthesized. Thus, the intramolecular reductive cyclization of o-silyl-substituted bis(phenylethynyl)benzenes with lithium naphthalenide produces partially silicon-bridged bis(styryl)benzenes consisting of silaindene or disilaindacene skeletons. By combining this cyclization with the Friedel-Crafts type electrophilic cyclization, a homologous series of the fully fused LOPVs and related compounds, bearing silicon and carbon bridges, has been synthesized in fairly good yields. The longest example of the LOPVs is the 13-ring-fused system that has a nearly flat pi-conjugated framework with a length of 2.9 nm, as proven by X-ray crystallography. All the produced ladder pi-electron systems show intense fluorescence in the visible region with high quantum yields as well as relatively small Stokes shifts. As the silicon contents increase or the disilaindacene skeleton is incorporated, the emission maxima shift to the longer wavelengths and the fluorescent quantum yields slightly decrease. These trends can be rationalized as due to the sigma* effect of silicon, wherein the silicon bridges contribute to the electronic structure through sigma*-pi* orbital interaction that cause the red-shifts ill the emission maxima and suppress the radiative decay process from the singlet excited state. (c) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jorganchem.2005.05.019

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  276. General synthesis of thiophene and selenophene-based heteroacenes

    T Okamoto, K Kudoh, A Wakamiya, S Yamaguchi

    ORGANIC LETTERS   Vol. 7 ( 23 ) page: 5301 - 5304   2005.11

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    A new intramolecular triple cyclization of bis(o-haloaryl)diacetylenes, via dilithiation followed by reaction with chalcogen elements, produces pi-conjugated compounds containing heterole-1,2-dichalcogenin-heterole fused tricyclic skeletons. The subsequent dechalcogenation with copper metal affords a series of thiophene- and selenophene-based heteroacenes.

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  277. The chemistry of silicon-containing ladder pi-conjugated systems

    Yamaguchi S, Xu CH

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   Vol. 63 ( 11 ) page: 1115 - 1123   2005.11

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  278. The chemistry of silicon-containing ladder pi-conjugated systems

    S Yamaguchi, CH Xu

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   Vol. 63 ( 11 ) page: 1115 - 1123   2005.11

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    The intramolecular reductive cyclization of bis(o-silylphenyl)acetylenes with lithium naphthalenide produces bis-silicon-bridged stilbenes. Based on this new cyclization, a series of silicon-bridged ladder pi-conjugated systems consisting of the p-phenylenevinylene framework have been synthesized, including the partially or fully silicon-bridged bis (styryl) benzenes, extended ladder oligo(p-phenylenevinylene)s, and bis-silicon-bridged stilbene-based pi-conjugated polymers. All the ladder pi-electron systems show intense fluorescence in the visible region. The detailed elucidation of their photophysical properties revealed the significant effect of the silicon moieties on the fluorescence properties.

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  279. Toward pi-conjugated molecule bundles: Synthesis of a series of B,B ',B ''-trianthryl-N,N ',N ''-triarylborazines and the bundle effects on their properties

    Wakamiya A, Ide T, Yamaguchi S

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 127 ( 42 ) page: 14859 - 14866   2005.10

  280. Solubilization by different-sized surfactant mixtures.

    Yamaguchi S

    Journal of colloid and interface science   Vol. 286 ( 1 ) page: 355 - 9   2005.6

  281. Ladder oligo(p-phenylenevinylene)s with silicon and carbon bridges

    CH Xu, A Wakamiya, S Yamaguchi

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 127 ( 6 ) page: 1638 - 1639   2005.2

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    DOI: 10.1021/ja042964m

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  282. A key role of orbital interaction in the main group element-containing pi-electron systems

    Yamaguchi S, Tamao K

    CHEMISTRY LETTERS   Vol. 34 ( 1 ) page: 2 - 7   2005.1

  283. General Synthesis of Thiophene and Selenophene-Based Heteroacenes

    T. Okamoto, K. Kudoh, A. Wakamiya, and S. Yamaguchi

    Org. Lett.   Vol. 7   page: 5301-5304   2005

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  284. The Chemistry of Silicon-Containing Ladder p-Conjugated Systems

    S. Yamaguchi and C. Xu

      Vol. 63   page: 1115-1123   2005

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  285. Toward pi-Conjugated Molecular Bundles: Synthesis of a Series of B,B',B"-Trianthryl-N,N',N"-triarylborazines and the Bundle Effects on their Properties

    A. Wakamiya, T. Ide, and S. Yamaguchi

    J. Am. Chem. Soc   Vol. 127   page: 14859-14866   2005

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  286. Synthesis, Structures, and Photophysical Properties of Silicon and Carbon-Bridged Ladder Oligo(p-phenylenevinylene)s and Related pi-Electron Systems

    S. Yamaguchi, C. Xu, H. Yamada, and A. Wakamiya

      Vol. 690   page: 5365-5377   2005

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  287. A Key Role of Orbital Interaction in the Main Group Element-Containing &#61552;-Electron Systems

    S. Yamaguchi and K. Tamao

    Chem. Lett.   Vol. 34   page: 2-7   2005

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  288. Ladder Oligo(p-phenylenevinylene)s with Silicon and Carbon Bridges

    C. Xu, A. Wakamiya, and S. Yamaguchi

    J. Am. Chem. Soc.   Vol. 127   page: 1638-1639   2005

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  289. A Key Role of Orbital Interaction in the Main Group Element-Containing -Electron Systems

    S. Yamaguchi, K. Tamao

    Chem. Lett.   Vol. 34   page: 2-7   2005

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  290. Ladder bis-silicon-bridged stilbenes as a new building unit for fluorescent pi-conjugated polymers

    CH Xu, H Yamada, A Wakamiya, S Yamaguchi, K Tamao

    MACROMOLECULES   Vol. 37 ( 24 ) page: 8978 - 8983   2004.11

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    pi-Conjugated polymers containing the bis-silicon-bridged stilbene (5,10-dihydro-5,10-disilaindeno[2,1-a]indene) skeleton in the main chain have been synthesized. Our synthesis uses 3,8-dimethoxy derivatives (2) and 3,8-difluoro derivatives (3) of the bis-silicon-bridged stilbene as the key precursors. Thus, their regioselective ortho-metalation reactions with appropriate bases (sec-butyllithium for 2 and (LiBu2ZnTMP)-Bu-t for 3) followed by quenching with electrophiles afford various 2,7-difunctionalized bis-silicon-bridged stilbenes. By using the 2,7-difunctionalized derivatives as starting materials, a series of pi-conjugated polymers, including homopolymers of the bis-silicon-bridged stilbene skeleton and copolymers between the bis-silicon-bridged stilbene unit and other types of monomer units, such as bithiophene and diethynylbenzene, have been synthesized by cross-coupling methodologies. While all the homopolymers of the bis-silicon-bridged stilbene skeleton exhibit an intense blue to greenish-blue emission, the copolymers with the bithiophene and diethynylbenzene units show green and orange emissions, respectively, suggesting easy tuning of the emission colors over a wide range.

    DOI: 10.1021/ma0486546

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  291. General Silaindene Synthesis Based on Intramolecular Reductive Cyclization: Synthesis of New Fluorescent Silicon-Containing p-Electron Systems Reviewed

    C. Xu, A. Wakamiya, S. Yamaguchi

    Org. Lett., 6, 3707-3710   Vol. 6 ( 21 ) page: 3707 - 3710   2004.10

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  292. All-anti Pentasilane: Conformation Control of Oligosilanes Based on Bis(tetramethylene)-tethered Trisilane Unit Reviewed

    Hayato Tsuji, Aiko Fukazawa, Shigehiro Yamaguchi, Akio Toshimitsu, Kohei Tamao

    Organometallics   Vol. 23 ( 14 ) page: 3375 - 3377   2004.7

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    DOI: 10.1021/om049695t

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  293. First Br-4 four centre-six electron and Se2Br5 seven centre-ten electron bonds in nonionic bromine adducts of selenanthrene

    Nakanishi W, Hayashi S, Yamaguchi S, Tamao K

    CHEMICAL COMMUNICATIONS   ( 2 ) page: 140 - 141   2004.1

  294. Ladder Bis-Silicon-Bridged Stilbenes as a New Building Unit for Fluorescent pi-Conjugated Polymers

    C. Xu, H. Yamada, A. Wakamiya, S. Yamaguchi, and K. Tamao

    Macromolecules   Vol. 37   page: 8978-8983   2004

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    Language:English   Publishing type:Research paper (scientific journal)  

  295. Endo-endo mode intramolecular reductive cyclization of cyclic 1,2-bis(silylethynyl)benzenes

    Yamaguchi S, Miyasato M, Tamao K

    CHEMISTRY LETTERS   Vol. 32 ( 12 ) page: 1104 - 1105   2003.12

  296. Bis-Silicon-Bridged Stilbene Homologues Synthesized by New Intramolecular Reductive Double Cyclization

    S. Yamaguchi, C, Xu, and K. Tamao,

    J. Am. Chem. Soc.   Vol. 125   page: 13662-13663   2003

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  297. The double N-arylation of primary amines: Toward multisubstituted carbazoles with unique optical properties

    Nozaki K, Takahashi K, Nakano K, Hiyama T, Tang HZ, Fujiki M, Yamaguchi S, Tamao K

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 42 ( 18 ) page: 2051 - 2053   2003

  298. A colorimetric and ratiometric fluorescent chemosensor with three emission changes: Fluoride ion sensing by a triarylborane-porphyrin conjugate

    Kubo Y, Yamamoto M, Ikeda M, Takeuchi M, Shinkai S, Yamaguchi S, Tamao K

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 42 ( 18 ) page: 2036 - 2040   2003

  299. Dibenzoborole-containing pi-electron systems: Remarkable fluorescence change based on the "on/off" control of the p(pi)-pi* conjugation

    Yamaguchi S, Shirasaka T, Akiyama S, Tamao K

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 124 ( 30 ) page: 8816 - 8817   2002.7

  300. Cross-coupling reactions in the chemistry of silole-containing pi-conjugated oligomers and polymers

    Yamaguchi S, Tamao K

    JOURNAL OF ORGANOMETALLIC CHEMISTRY   Vol. 653 ( 1-2 ) page: 223 - 228   2002.7

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  301. Synthesis, structures, and UV-visible absorption spectra of tri(9-anthryl)bismuthine derivatives

    Yamaguchi S, Shirasaka T, Tamao K

    ORGANOMETALLICS   Vol. 21 ( 12 ) page: 2555 - 2558   2002.6

  302. A new approach to photophysical properties control of main group element pi-electron compounds based on the coordination number change

    Yamaguchi S, Akiyama S, Tamao K

    JOURNAL OF ORGANOMETALLIC CHEMISTRY   Vol. 652 ( 1-2 ) page: 3 - 9   2002.6

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  303. The coordination number-photophysical properties relationship of trianthrylphosphorus compounds: doubly locked fluorescence of anthryl groups

    Yamaguchi S, Akiyama S, Tamao K

    JOURNAL OF ORGANOMETALLIC CHEMISTRY   Vol. 646 ( 1-2 ) page: 277 - 281   2002.3

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  304. Dibenzoborole-Containing &#61552;-Electron Systems: Remarkable Fluorescence Change Based on the ON/OFF-Control of the p&#61552;-&#61552;* Conjugation

    S. Yamaguchi, T. Shirasaka, S. Akiyama, and K. Tamao

    J. Am. Chem. Soc.   Vol. 124   page: 8816-8817   2002

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  305. Colorimetric fluoride ion sensing by boron-containing pi-electron systems

    Yamaguchi S, Akiyama S, Tamao K

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 123 ( 46 ) page: 11372 - 11375   2001.11

  306. The first alkali metal selenothioates: Synthesis and molecular structure

    Niyomura O, Sakai K, Murai T, Kato S, Yamaguchi S, Tamao K

    CHEMISTRY LETTERS   ( 10 ) page: 968 - 969   2001.10

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  307. Structural optimization of 2,5-diarylsiloles as excellent electron-transporting materials for organic electroluminescent devices

    Uchida M, Izumizawa T, Nakano T, Yamaguchi S, Tamao K, Furukawa K

    CHEMISTRY OF MATERIALS   Vol. 13 ( 8 ) page: 2680 - 2683   2001.8

  308. Diphenylamino-substituted 2,5-diarylsiloles for single-layer organic electroluminescent devices

    Yamaguchi S, Endo T, Uchida M, Izumizawa T, Furukawa K, Tamao K

    CHEMISTRY LETTERS   ( 2 ) page: 98 - 99   2001.2

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  309. Tridurylboranes extended by three arylethynyl groups as a new family of boron-based pi-electron systems

    Yamaguchi S, Shirasaka T, Tamao K

    ORGANIC LETTERS   Vol. 2 ( 26 ) page: 4129 - 4132   2000.12

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  310. Introduction to the chemistry of interelement linkage

    Tamao K, Yamaguchi S

    JOURNAL OF ORGANOMETALLIC CHEMISTRY   Vol. 611 ( 1-2 ) page: 3 - 4   2000.10

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  311. New type of polysilanes: poly(1,1-silole)s

    Tamao K, Yamaguchi S

    JOURNAL OF ORGANOMETALLIC CHEMISTRY   Vol. 611 ( 1-2 ) page: 5 - 11   2000.10

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  312. Photophysical properties changes caused by hypercoordination of organosilicon compounds: From trianthrylfluorosilane to trianthryldifluorosilicate

    Yamaguchi S, Akiyama S, Tamao K

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 122 ( 28 ) page: 6793 - 6794   2000.7

  313. Tri-9-anthrylborane and its derivatives: New boron-containing pi-electron systems with divergently extended pi-conjugation through boron

    Yamaguchi S, Akiyama S, Tamao K

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 122 ( 26 ) page: 6335 - 6336   2000.7

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  314. Toward new materials for organic electroluminescent devices: Synthesis, structures, and properties of a series of 2,5-diaryl-3,4-diphenylsiloles

    Yamaguchi S, Endo T, Uchida M, Izumizawa T, Furukawa K, Tamao K

    CHEMISTRY-A EUROPEAN JOURNAL   Vol. 6 ( 9 ) page: 1683 - 1692   2000.5

  315. Silole-thiophene alternating copolymers with narrow band gaps

    Yamaguchi S, Goto T, Tamao K

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 39 ( 9 ) page: 1695 - +   2000

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  316. Conformation control of oligosilanes based on configurationally constrained bicyclic disilane units

    Tamao K, Tsuji H, Terada M, Asahara M, Yamaguchi S, Toshimitsu A

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   Vol. 39 ( 18 ) page: 3287 - +   2000

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  317. The first synthesis of well-defined poly(2,5-silole)

    Yamaguchi S, Jin RZ, Itami Y, Goto T, Tamao K

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 121 ( 44 ) page: 10420 - 10421   1999.11

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  318. Effect of countercation inclusion by [2.2.2]cryptand upon stabilization of potassium organofluorosilicates

    Yamaguchi S, Akiyama S, Tamao K

    ORGANOMETALLICS   Vol. 18 ( 15 ) page: 2851 - 2854   1999.7

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  319. A new chiral molecular square with D-4 symmetry composed of enantiomerically pure spirosilane

    Yamaguchi S, Ishii H, Tamao K

    CHEMISTRY LETTERS   ( 5 ) page: 399 - 400   1999.5

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  320. Silole polymer and cyclic hexamer catenating through the ring silicons

    Yamaguchi S, Jin RZ, Tamao K

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 121 ( 12 ) page: 2937 - 2938   1999.3

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  321. A convenient one-pot synthesis of 1,4-dihalobutadienes from alkynes via titanacyclopentadienes and their transformation to a series of silole derivatives

    Yamaguchi S, Jin RZ, Tamao K, Sato F

    JOURNAL OF ORGANIC CHEMISTRY   Vol. 63 ( 26 ) page: 10060 - 10062   1998.12

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  322. From tellurophenes to siloles. Synthesis, structures, and photophysical properties of 3,4-unsubstituted 2,5-diarylsiloles

    Katkevics M, Yamaguchi S, Toshimitsu A, Tamao K

    ORGANOMETALLICS   Vol. 17 ( 26 ) page: 5796 - 5800   1998.12

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  323. Silole-containing sigma- and pi-conjugated compounds

    Yamaguchi S, Tamao K

    JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS   ( 22 ) page: 3693 - 3702   1998.11

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  324. Halodesilylation route to 2,5-difunctionalized 3,4-dialkylsiloles and their derivatization to 2,2 '-bisilole

    Yamaguchi S, Jin RZ, Ohno S, Tamao K

    ORGANOMETALLICS   Vol. 17 ( 23 ) page: 5133 - 5138   1998.11

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  325. Group 14 metalloles with thienyl groups on 2,5-positions: Effects of group 14 elements on their pi-electronic structures

    Yamaguchi S, Itami Y, Tamao K

    ORGANOMETALLICS   Vol. 17 ( 22 ) page: 4910 - 4916   1998.10

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  326. Synthesis, structures, photophysical properties, and dynamic stereochemistry of tri-9-anthrylsilane derivatives

    Yamaguchi S, Akiyama S, Tamao K

    ORGANOMETALLICS   Vol. 17 ( 20 ) page: 4347 - 4352   1998.9

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  327. Synthesis and properties of silole-containing alpha- and pi-conjugated compounds

    Yamaguchi S, Tamao K

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   Vol. 56 ( 6 ) page: 500 - 510   1998.6

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  328. Modification of the electronic structure of silole by the substituents on the ring silicon

    Yamaguchi S, Jin RZ, Tamao K

    JOURNAL OF ORGANOMETALLIC CHEMISTRY   Vol. 559 ( 1-2 ) page: 73 - 80   1998.5

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  329. Silole-acetylene pi-electronic systems with low bandgaps: Synthesis, structure, and UV-vis absorption spectra of 2,5-diethynylsiloles derivatives and their polymers

    Yamaguchi S, Iimura K, Tamao K

    CHEMISTRY LETTERS   ( 1 ) page: 89 - 90   1998

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  330. Pd(II)-catalyzed oxidative homo-coupling of aryl-metal compounds using acrylate dibromide derivatives as effective oxidants

    Yamaguchi S, Ohno S, Tamao K

    SYNLETT   ( 10 ) page: 1199 - &   1997.10

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  331. Silicon-catenated silole oligomers: Oligo(1,1-silole)s

    Yamaguchi S, Jin RZ, Tamao K, Shiro M

    ORGANOMETALLICS   Vol. 16 ( 12 ) page: 2486 - 2488   1997.6

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  332. Synthesis of a series of 1,1-difunctionalized siloles

    Yamaguchi S, Jin RZ, Tamao K, Shiro M

    ORGANOMETALLICS   Vol. 16 ( 11 ) page: 2230 - 2232   1997.5

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  333. Regioselective synthesis of polyfunctionalized alkyltrisilanes and -tetrasilanes via reductive cross-coupling reaction of aminoalkylsilyl chlorides with lithium

    Tamao K, Sun GR, Kawachi A, Yamaguchi S

    ORGANOMETALLICS   Vol. 16 ( 4 ) page: 780 - 788   1997.2

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  334. A new example of linear disiloxane: Synthesis and X-ray crystal structure of bis(2-silolyl)tetramethyldisiloxane

    Yamaguchi S, Jin RZ, Shiro M, Tamao K

    KHIMIYA GETEROTSIKLICHESKIKH SOEDINENII   ( 2 ) page: 180 - 185   1997.2

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  335. Axially chiral spirosilanes via catalytic asymmetric intramolecular hydrosilation

    Tamao K, Nakamura K, Ishii H, Yamaguchi S, Shiro M

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 118 ( 49 ) page: 12469 - 12470   1996.12

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  336. Silole derivatives as efficient electron transporting materials

    Tamao K, Uchida M, Izumizawa T, Furukawa K, Yamaguchi S

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 118 ( 47 ) page: 11974 - 11975   1996.11

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  337. Silole-pyrrole co-oligomers: Their synthesis, structure and UV-VIS absorption spectral

    Tamao K, Ohno S, Yamaguchi S

    CHEMICAL COMMUNICATIONS   ( 16 ) page: 1873 - 1874   1996.8

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  338. Theoretical study of the electronic structure of 2,2'-bisilole in comparison with 1,1'-Bi-1,3-cyclopentadiene: sigma*-pi* conjugation and a low-lying LUMO as the origin of the unusual optical properties of 3,3',4,4'-tetraphenyl-2,2'-bisilole

    Yamaguchi S, Tamao K

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   Vol. 69 ( 8 ) page: 2327 - 2334   1996.8

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  339. Synthesis, structure, and absorption spectra of the well-defined 1,1'-bicyclopentadiene derivatives

    Yamaguchi S, Tamao K

    TETRAHEDRON LETTERS   Vol. 37 ( 17 ) page: 2983 - 2986   1996.4

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  340. Regio-controlled intramolecular reductive cyclization of diynes

    Tamao K, Yamaguchi S

    PURE AND APPLIED CHEMISTRY   Vol. 68 ( 1 ) page: 139 - 144   1996.1

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  341. New chiral diphosphines, 2,3-bis(siloxy)-1,4-bis(diphenylphosphino)butanes, and their cationic Rh(I) complexes: Synthesis and structures

    Tamao K, Nakamura K, Yamaguchi S, Shiro M, Saito S

    CHEMISTRY LETTERS   ( 11 ) page: 1007 - 1008   1996

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  342. SILOLE-CONTAINING PI-CONJUGATED SYSTEMS .3. A SERIES OF SILOLE-THIOPHENE COOLIGOMERS AND COPOLYMERS - SYNTHESIS, PROPERTIES, AND ELECTRONIC-STRUCTURES

    TAMAO K, YAMAGUCHI S, ITO Y, MATSUZAKI Y, YAMABE T, FUKUSHIMA M, MORI S

    MACROMOLECULES   Vol. 28 ( 25 ) page: 8668 - 8675   1995.12

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  343. OLIGOSILOLES - FIRST SYNTHESIS BASED ON A NOVEL ENDO-ENDO MODE INTRAMOLECULAR REDUCTIVE CYCLIZATION OF DIETHYNYLSILANES

    TAMAO K, YAMAGUCHI S, SHIRO M

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 116 ( 26 ) page: 11715 - 11722   1994.12

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  344. SYNTHESIS AND PROPERTIES OF THIOPHENE CYCLOPENTADIENONE COOLIGOMERS

    TAMAO K, YAMAGUCHI S, ITO Y

    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS   ( 2 ) page: 229 - 230   1994.1

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  345. THIOPHENE SILOLE COOLIGOMERS AND COPOLYMERS

    TAMAO K, YAMAGUCHI S, SHIOZAKI M, NAKAGAWA Y, ITO Y

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   Vol. 114 ( 14 ) page: 5867 - 5869   1992.7

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Presentations 22

  1. Ladder pi-Electron Materials with Main Group Elements

    Nagoya University 21st Century COE-RCMS International Conference on Elucidation and Creation of Molecular Functions 

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    Event date: 2007

    Language:English  

    Country:Japan  

  2. 光電子機能材料としての典型元素化合物の可能性

    近畿化学協会ヘテロ原子部会平成19年度第2回懇話会 

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    Event date: 2007

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  3. New pi-Conjugated Systems with Main Group Elements International conference

    The International Workshop on Electron Transport through a Linked Molecule in Nano-Scale 

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    Event date: 2007

    Language:English  

    Country:Japan  

  4. Phosphoryl-Bridged Stilbene as a New Ladder pi-Electron Materials International conference

    The 8th International Conference on Heteroatom Chemistry (ICHAC-8) 

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    Event date: 2007

    Language:English  

  5. New π-conjugated materials with main group elements International conference

    Pre-symposium of ISNA-12 in Tokyo "Novel π-Systems, Novel Properties ", 

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    Event date: 2007

    Language:English   Presentation type:Oral presentation (general)  

    Country:Japan  

  6. 典型元素を使った光・電子機能分子合成

    第34回有機金属セミナー, 有機金属化合物の使い方とコツ 

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    Event date: 2007

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  7. パイ電子系の化学:典型元素を用いた物性修飾

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    Event date: 2007

    Language:Japanese  

    Country:Japan  

  8. 典型元素を含むパイ共役電子系の化学

    有機合成2月セミナー - 有機合成のニュートレンド 2007- 

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    Event date: 2007

    Language:Japanese  

    Country:Japan  

  9. 元素にこだわった機能分子の合成

    JEOL 第16回 NMR ユーザーズミーティング 

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    Event date: 2007

    Language:Japanese  

    Country:Japan  

  10. 典型元素を機軸とする機能性パイ電子系の創製

    大学間連携事業 物質合成研究拠点機関連携事業 第2回物質合成シンポジウム「機能性材料を指向した物質合成の化学」 

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    Event date: 2007

    Language:Japanese  

    Country:Japan  

  11. Design and Synthesis of Boron-Based pi-Electron Materials

    2006 Japan-Taiwan Joint Symposium on Organometallic Chemistry 

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    Event date: 2006

    Language:English  

  12. 典型元素を使った新機能分子のデザイン

    有機合成化学協会有機合成講習会 

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    Event date: 2006

    Language:Japanese  

    Country:Japan  

  13. ホウ素を鍵にした機能物質の合成化学

    第16回福岡万有シンポジウム 

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    Event date: 2006

    Language:Japanese  

    Country:Japan  

  14. 光電子機能材料を指向した典型元素化学

    有機合成化学協会中国四国支部 第59回パネル討論会 

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    Event date: 2006

    Language:Japanese  

  15. 典型元素を含むラダーπ電子系の化学

    SORSTジョイントシンポジウム 

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    Event date: 2006

    Language:Japanese  

  16. ラダーπ電子系の合成化学

    物性研究所短期研究会 

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    Event date: 2006

    Language:Japanese  

  17. 典型元素の特性を活かした光・電子機能分子の合成化学

    日本化学会関東支部講演会「匠に学ぶ有機合成の新しい技」 

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    Event date: 2006

    Language:Japanese  

    Country:Japan  

  18. Ladder π-Electron Materials with Silicon and Sulfur Bridges International conference

    10th International Kyoto Conference on New Aspects of Organic Chemistry (IKCOC-10) 

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    Event date: 2006

    Language:English  

    Country:Japan  

  19. Recent Progress in the Functional Organoboron Materials

    2nd BASF Boron Conference 

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    Event date: 2006

    Language:English  

    Country:Japan  

  20. Functional Organoelement Materials: Design and Synthesis International conference

    4th Spanish-Portuguese-Japanese Organic Chemistry Symposium 

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    Event date: 2006

    Language:English  

  21. 機能典型元素化学:光・電子機能材料の新設計

    錯体化学若手の会夏の学校2006 

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    Event date: 2006

    Language:Japanese  

    Country:Japan  

  22. ケイ素,ホウ素を含む光・電子機能分子の設計と合成

    高分子学会印刷・情報記録・表示研究会講演会 

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    Event date: 2006

    Language:Japanese  

    Country:Japan  

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KAKENHI (Grants-in-Aid for Scientific Research) 3

  1. 未踏物性発現を目指したπ電子系化学                       

    2007

    科学研究費補助金  若手研究(S),課題番号:19675001

    山口 茂弘

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    Authorship:Principal investigator 

  2. 「典型的元素を含む新規ラダー型π電子系化合物の合成と性質」

    2006

    科学研究費補助金  特別研究員奨励費,課題番号:68006341

    山口 茂弘

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    Authorship:Principal investigator 

  3. 14族元素を含む新規パイ共役高分子の開発

    Grant number:08751002  1996

    奨励研究(A)

    山口 茂弘

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    Authorship:Principal investigator 

    Grant amount:\1100000 ( Direct Cost: \1100000 )

    シロール(シラシクロペンタジエン)環は、環内のσ^*-π^*共役に起因した著しく低いLUMOレベル,すなわち,高い電子受容性をもつ特異なパイ電子系である.これまで,シロール環を基本構成単位とする種々のパイ電子系化合物の開発を行ってきた.特に,電子供与性のチオフェンとの組み合わせから成る2,5-ジチエルシロールおよびその共重合体は,特異な光学特性および高い電子輸送特性を有することを明らかにしている.本研究では,2,5位にチエニル基を有する一連の14族メタロール(シロール,ゲルモ-ル,スタンノール)の合成を行い,新規パイ共役高分子のモノマーユニットとしての可能性について検討した.本研究で得られた成果は以下のようにまとめられる.
    1.2,5-ジチエニルメタロールの合成
    チエニル基を末端に持つ1,6-ヘプタジイン誘導体とヒドロジシランとのニッケル触媒環化反応により2,5-ジチエニルシロールを,また,相当するジルコナシクロペンタジエンからのトランスメタル化により2,5-ジチエニルゲルモ-ルおよびスタンノール合成することに成功した.
    2.2,5-ジチエニルメタロールの結晶構造解析
    2,5-ジチエニルゲルモ-ルおよびスタンノールの結晶構造解析により,いずれの場合も,チオフェン-メタロール-チオフェンの3つの環は,高い共平面性を持つことが明らかになった.
    2,5-ジチエニルメタロールの光学特性および酸化還元特性
    得られたメタロールについて,紫外可視スペクトル,蛍光スペクトル,および酸化還元電位の測定を行った.いずれのメタロールも400nm付近および480nm付近に強い吸収および蛍光を有しており,これらの値は,類似した骨格を持つ1,4-ジチエニルブタジエン誘導体と比較して約30nmも長波長の値となっている.このことから,パイ電子構造に対して14族中心元素が大きく寄与していることがうかがえる.しかし,ケイ素,ゲルマニウム,およびスズの与える影響の差は小さいと言える.この結果と一致して,いずれのメタロールもほぼ同様の酸化還元特性を示した.

 

Teaching Experience (On-campus) 1

  1. 有機化学Ⅰ

    2016