Faculty Profiles - YAMAGUCHI, Shigehiro

Papers - YAMAGUCHI, Shigehiro

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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

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

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.

DOI： 10.1021/jp209264j

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PubMed

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

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

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.

DOI： 10.1021/ol2033916

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Scopus

PubMed

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

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

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

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.

DOI： 10.1039/c2cc35874c

Web of Science

PubMed

J-GLOBAL

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

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

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

Web of Science

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

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

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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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

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

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

Electron-Donating Tetrathienyl-Substituted Borole Reviewed

Takafumi Araki, Aiko Fukazawa, Shigehiro Yamaguchi

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

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

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

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).

DOI： 10.1039/c2ob25199j

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PubMed

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

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

Yamaguchi Shigehiro, Fukazawa Aiko

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

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：SOC SYNTHETIC ORGANIC CHEM JPN

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

Web of Science

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

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

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

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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J-GLOBAL

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

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

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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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

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

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

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

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

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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PubMed

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Papers - YAMAGUCHI, Shigehiro