Faculty Profiles - YAMAGUCHI, Shigehiro

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

J-GLOBAL

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

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

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

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.

DOI： 10.1021/ol302742g