Faculty Profiles - YAMAGUCHI, Shigehiro

Papers - YAMAGUCHI, Shigehiro

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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

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

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

Web of Science

PubMed

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

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

COD ID: 4120128 Reviewed

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

Crystallography Open Database 2014

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

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

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

Web of Science

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

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.

DOI： 10.1021/ol403084x

Web of Science

PubMed

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

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.

DOI： 10.1021/jo401748d

Web of Science

PubMed

A Radical Anion of Structurally Constrained Triphenylborane

Tomokatsu Kushida, Shigehiro Yamaguchi

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

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

Web of Science

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

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

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

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

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.

DOI： 10.1002/anie.201303738

Web of Science

Scopus

PubMed

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

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

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

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

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

Web of Science

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

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

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

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

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.

DOI： 10.1021/ja4055228

Web of Science

PubMed

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

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.

DOI： 10.1021/ja404724f

Web of Science

Scopus

PubMed

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

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

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

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

Web of Science

PubMed

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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Papers - YAMAGUCHI, Shigehiro