Faculty Profiles - YAMAGUCHI, Shigehiro

Papers - YAMAGUCHI, Shigehiro

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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

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

Web of Science

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

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

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

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

Web of Science

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

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

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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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

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

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

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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PubMed

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

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

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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PubMed

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

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

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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PubMed

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

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

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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PubMed

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

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

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

Web of Science

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

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

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

Web of Science

PubMed

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

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

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

Web of Science

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

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

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

Web of Science

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Papers - YAMAGUCHI, Shigehiro