Faculty Profiles - YAMAGUCHI, Shigehiro

Papers - YAMAGUCHI, Shigehiro

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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

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

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

Web of Science

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

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

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

Web of Science

PubMed

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

Kinetically Stabilized Dibenzoborole as an Electron-Accepting Building Unit Open Access

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

Chem. Commun., page： 579-581 2008

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

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

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

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

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

Design and Synthesis of Boron-Containing Functional pi-Electron Materials Open Access

A. Wakamiya, and S. Yamaguchi

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

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

*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

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

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL

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

Web of Science

PubMed

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

Kinetically stabilized dibenzoborole as an electron-accepting building unit

Atsushi Wakamiya, Kotaro Mishima, Kanako Ekawa, Shigehiro Yamaguchi

CHEMICAL COMMUNICATIONS ( 5 ) page： 579 - 581 2008

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

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

Web of Science

PubMed

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

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

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

Web of Science

PubMed

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

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

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.

DOI： 10.1021/jp067262t

Web of Science

PubMed

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

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

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

Web of Science

PubMed

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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Papers - YAMAGUCHI, Shigehiro