Faculty Profiles - YAMAGUCHI, Shigehiro

Papers - YAMAGUCHI, Shigehiro

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Steric Shielding vs Structural Constraint in a Boron-Containing Polycyclic Aromatic Hydrocarbon Reviewed

V. M. Hertz, N. Ando, M. Hirai, M. Bolte, H.-W. Lerner, S. Yamaguchi, M. Wagner

Organometallics 2016.12

Stable Red-Emissive Cationic Dithienotropylium Dyes Reviewed

Kengo Asai, Aiko Fukazawa, Shigehiro Yamaguchi

CHEMISTRY-A EUROPEAN JOURNAL Vol. 22 ( 49 ) page： 17571 - 17575 2016.12

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

A series of thiophene-fused tropylium ions, containing various electron-donating amino groups at the terminal positions, was synthesized. The fusion of the thiophene rings, as well as the presence of the terminal amino groups endows the cationic tropylium ion with excellent stability and high pK(R)(+) values. X-ray crystallographic analysis of these compounds revealed a pronounced quinoidal character for the amino-substituted dithienotropylium skeletons. These compounds exhibit attractive photophysical properties such as strong absorption in the visible region combined with red fluorescence. Theoretical calculations suggested that the 3,3'-bithiophene substructure should be crucial for attaining these photophysical properties.

DOI： 10.1002/chem.201604509

Web of Science

PubMed

A Soluble Dynamic Complex Strategy for the Solution-Processed Fabrication of Organic Thin-Film Transistors of a Boron-Containing Polycyclic Aromatic Hydrocarbon Reviewed

K. Matsuo, S. Saito, S. Yamaguchi

Angew. Chem. Int. Ed. Vol. 55 ( 39 ) page： 11984 - 11988 2016.9

Light-melt adhesive based on dynamic carbon frameworks in a columnar liquid-crystal phase Reviewed Open Access

Shohei Saito, Shunpei Nobusue, Eri Tsuzaka, Chunxue Yuan, Chigusa Mori, Mitsuo Hara, Takahiro Seki, Cristopher Camacho, Stephan Irle, Shigehiro Yamaguchi

NATURE COMMUNICATIONS Vol. 7 page： 12094 2016.7

Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

Liquid crystal (LC) provides a suitable platform to exploit structural motions of molecules in a condensed phase. Amplification of the structural changes enables a variety of technologies not only in LC displays but also in other applications. Until very recently, however, a practical use of LCs for removable adhesives has not been explored, although a spontaneous disorganization of LC materials can be easily triggered by light-induced isomerization of photoactive components. The difficulty of such application derives from the requirements for simultaneous implementation of sufficient bonding strength and its rapid disappearance by photoirradiation. Here we report a dynamic molecular LC material that meets these requirements. Columnar-stacked V-shaped carbon frameworks display sufficient bonding strength even during heating conditions, while its bonding ability is immediately lost by a light-induced self-melting function. The light-melt adhesive is reusable and its fluorescence colour reversibly changes during the cycle, visualizing the bonding/nonbonding phases of the adhesive.

DOI： 10.1038/ncomms12094

Open Access

Web of Science

PubMed

A Macrocyclic Fluorophore Dimer with Flexible Linkers: Bright Excimer Emission with a Long Fluorescence Lifetime Reviewed

Hiroshi Osaki, Chih-Ming Chou, Masayasu Taki, Kai Welke, Daisuke Yokogawa, Stephan Irle, Yoshikatsu Sato, Tetsuya Higashiyama, Shohei Saito, Aiko Fukazawa, Shigehiro Yamaguchi

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 55 ( 25 ) page： 7131 - 7135 2016.6

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

Bright fluorescent molecules with long fluorescence lifetimes are important for the development of lifetime-based fluorescence imaging techniques. Herein, a molecular design is described for simultaneously attaining long fluorescence lifetime (tau) and high brightness (Phi(F) x epsilon) in a system that features macrocyclic dimerization of fluorescent p-conjugated skeletons with flexible linkers. An alkylene-linked macrocyclic dimer of bis(thienylethynyl)anthracene was found to show excimer emission with a long fluorescence lifetime (tau approximate to 19 ns) in solution, while maintaining high brightness. A comparison with various relevant derivatives revealed that the macrocyclic structure and the length of the alkylene chains play crucial roles in attaining these properties. In vitro time-gated imaging experiments were conducted as a proof-of-principle for the superiority of this macrocyclic fluorophore relative to the commercial fluorescent dye Alexa Fluor 488.

DOI： 10.1002/anie.201602239

Web of Science

PubMed

Pyridyl Directed Catalyst-Free trans-Hydroboration of Internal Alkynes Reviewed

Kang Yuan, Naoya Suzuki, Soren K. Mellerup, Xiang Wang, Shigehiro Yamaguchi, Suning Wang

ORGANIC LETTERS Vol. 18 ( 4 ) page： 720 - 723 2016.2

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

We report the first examples of straightforward trans-hydroboration of internal alkynes at room temperature with 9-BBN, producing five-membered BN-heterocycles. Contrary to conventional cis-hydroboration, we demonstrate that the introduction of a pyridyl group switches the stereoselectivity of the reaction. A hydride migration mechanism has been proposed and supported by DFT calculations for the trans-hydroboration. This new hydroboration approach allows facile construction of new blue fluorescent BN-heterocyclic compounds.

DOI： 10.1021/acs.orglett.5b03698

Web of Science

PubMed

A biphenyl containing two electron-donating and two electron-accepting moieties: a rigid and small donor-acceptor-donor ladder system Reviewed

Tobias W. Greulich, Naoya Suzuki, Constantin G. Daniliuc, Aiko Fukazawa, Eriko Yamaguchi, Armido Studer, Shigehiro Yamaguchi

CHEMICAL COMMUNICATIONS Vol. 52 ( 11 ) page： 2374 - 2377 2016

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

Ladder pi-conjugated materials and also push-pull systems belong to important classes of compounds for the development of organic electronic devices. In this communication, a novel pi-conjugated material that unifies the properties of both of these classes is presented. The material comprises a rigid biphenyl framework, which bears two bridging electron-accepting phosphine oxide moieties as well as two electron-donating amino groups. The structure and photophysical properties of this compound are discussed and compared with those of a related system lacking the second P-moiety.

DOI： 10.1039/c5cc03063c

Web of Science

PubMed

A planarized 9-phenylanthracene: a simple electron-donating building block for fluorescent materials Reviewed

Hideaki Iwahara, Tomokatsu Kushida, Shigehiro Yamaguchi

CHEMICAL COMMUNICATIONS Vol. 52 ( 6 ) page： 1124 - 1127 2016

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

A 9-phenylanthracene, constrained in a coplanar fashion by two methylene tethers, was synthesized and its optoelectronic properties were investigated. The rigid planarization increased its electron-donating character and induced a bathochromic shift of its absorption, as well as an increased molar absorption coefficient and intense fluorescence. These properties render this compound a promising building block for fluorescent materials.

DOI： 10.1039/c5cc08259e

Web of Science

PubMed

Phospha-fluorescein: a red-emissive fluorescein analogue with high photobleaching resistance Reviewed

Aiko Fukazawa, Shinji Suda, Masayasu Taki, Eriko Yamaguchi, Marek Grzybowski, Yoshikatsu Sato, Tetsuya Higashiyama, Shigehiro Yamaguchi

CHEMICAL COMMUNICATIONS Vol. 52 ( 6 ) page： 1120 - 1123 2016

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

Phospha-fluorescein (POF), a phosphine oxide-containing analogue of fluorescein, was synthesized and its photophysical properties were examined. Compared with fluorescein and sila-fluorescein, POF displayed significantly red-shifted absorption and fluorescence as well as superior photobleaching resistance, while retaining the pH-responsive characteristics of fluorescein dyes.

DOI： 10.1039/c5cc09345g

Web of Science

PubMed

Boron-doped nanographene: Lewis acidity, redox properties, and battery electrode performance Reviewed Open Access

Shinichiro Osumi, Shohei Saito, Chuandong Dou, Kyohei Matsuo, Keita Kume, Hirofumi Yoshikawa, Kunio Awagaa, Shigehiro Yamaguchi

CHEMICAL SCIENCE Vol. 7 ( 1 ) page： 219 - 227 2016

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

The preparation of boron-doped nanocarbon scaffolds with well-defined structures is important for the understanding of the impact of boron doping on their properties and behavior at the molecular level. We recently succeeded in the synthesis of a structurally well-defined nanographene molecule, bearing two boron atoms at the central positions. In this study, the characteristic properties and functions of this boron-doped nanographene were investigated in terms of (1) Lewis acidity, (2) redox properties, and (3) electrode performance in a battery. This boron-doped nanographene was susceptible to chemical adsorption with various Lewis bases, resulting in significant changes in the absorption and fluorescence properties, as well as in the conformation of the honeycomb framework. The two-electron reduction of this boron-doped nanographene produced a dianionic species that showed a substantial biradical character with a triplet ground state. A Li battery electrode, composed of a boron-doped nanographene with small peripheral substituents, displayed a stable performance in the 1.5-4.0 V range with a first discharge capacity of 160 mA h g(-1). These results provide important insights into the effect of boron doping on nanocarbon compounds.

DOI： 10.1039/c5sc02246k

Open Access

Web of Science

PubMed

A Phosphole Oxide Based Fluorescent Dye with Exceptional Resistance to Photobleaching: A Practical Tool for Continuous Imaging in STED Microscopy Reviewed

Chenguang Wang, Aiko Fukazawa, Masayasu Taki, Yoshikatsu Sato, Tetsuya Higashiyama, Shigehiro Yamaguchi

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 54 ( 50 ) page： 15213 - 15217 2015.12

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

The development of stimulated emission depletion (STED) microscopy represented a major breakthrough in cellular and molecular biology. However, the intense laser beams required for both excitation and STED usually provoke rapid photobleaching of fluorescent molecular probes, which significantly limits the performance and practical utility of STED microscopy. We herein developed a photoresistant fluorescent dye C-Naphox as a practical tool for STED imaging. With excitation using either a lambda = 405 or 488 nm laser in protic solvents, C-Naphox exhibited an intense red/orange fluorescence (quantum yield phi(F) > 0.7) with a large Stokes shift (circa 5900 cm(-1)). Even after irradiation with a Xe lamp (300 W, lambda(ex) = 460 nm, full width at half maximum (FWHM) = 11 nm) for 12 hours, 99.5 % of C-Naphox remained intact. The high photoresistance of C-Naphox allowed repeated STED imaging of HeLa cells. Even after recording 50 STED images, 83 % of the initial fluorescence intensity persisted.

DOI： 10.1002/anie.201507939

Web of Science

PubMed

A Benzophosphole P-Oxide with an Electron-Donating Group at 3-Position: Enhanced Fluorescence in Polar Solvents Reviewed

Eriko Yamaguchi, Aiko Fukazawa, Youhei Kosaka, Daisuke Yokogawa, Stephan Irle, Shigehiro Yamaguchi

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN Vol. 88 ( 11 ) page： 1545 - 1552 2015.11

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

Fluorophores with intramolecular charge-transfer (ICT) character in the excited state exhibit significant solvatochromism of their fluorescence. Here, we report an example for such compounds, a benzophosphole P-oxide bearing an electron-donating p-(diphenylamino)phenyl group at the 3-position. While this compound shows only subtle dependence of the absorption maximum on the solvent polarity (lambda(max) = 383-392 nm), its emission maximum is significantly red-shifted upon increasing the solvent polarity (cyclohexane: lambda(em) = 457 nm; DNIF: lambda(em) = 598 nm). Most notably, the fluorescence quantum yields gradually increase with increased Stokes shifts, ultimately reaching Phi(F) = 0.28 in DMF. This trend is fundamentally different from that observed for the corresponding 2-(diphenylamino)phenyl-substituted benzophosphole congener, for which applications as a fluorescent bioimaging probe were previously demonstrated. In this study, the origins of this striking difference are examined by a combined experimental and theoretical approach. Our results suggest that the observed difference arises from a significant contribution of quinoidal resonance forms in the ICT excited state, which suppresses nonradiative decay and hence increases the quantum yield in polar solvents.

DOI： 10.1246/bcsj.20150238

Web of Science

A Phosphole Oxide Based Fluorescent Dye with Exceptional Resistance to Photobleaching: A Practical Tool for Continuous Imaging in STED Microscopy Reviewed

C. Wang, A. Fukazawa, M. Taki, Yoshikatsu Sato, T. Higashiyama, S. Yamaguchi

Angew. Chem. Int. Ed. 2015.10

Designs of Functional pi-Electron Materials based on the Characteristic Features of Boron Reviewed Open Access

Atsushi Wakamiya, Shigehiro Yamaguchi

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN Vol. 88 ( 10 ) page： 1357 - 1377 2015.10

Language：Japanese Publisher：CHEMICAL SOC JAPAN

Boron, a group 13 element, has several characteristic structural and electronic features: 1) trivalent boron compounds usually adopt a trigonal planar geometry; 2) due to the presence of a vacant p-orbital, effective orbital interaction with pi-conjugated compounds is possible; 3) the presence of a vacant p-orbital is furthermore responsible for high Lewis acidity; 4) the boryl group acts as a pi-electron-accepting group particularly in the excited state. The consequent exploitation of these characteristic features of boron in the molecular design enables us to produce sophisticated pi-functional materials with attractive photophysical and electronic properties. This account article illustrates our systematic studies on the molecular design and the development of functional pi-electron materials using boron as a key element.

DOI： 10.1246/bcsj.20150151

Web of Science

Boron-Doped Nanographene: Lewis Acidity, Redox Properties, and Battery Electrode Performance Reviewed Open Access

S. Osumi, S. Saito, C. Dou, K. Matsuo, K. Kume, H. Yoshikawa, K. Awaga, S. Yamaguchi

Chem. Sci. 2015.9

Atomically-Controlled Substitutional Boron-Doping of Graphene Nanoribbons Reviewed Open Access

S. Kawai, S. Saito, S. Osumi, S. Yamaguchi, A. S. Foster, P. Spijker, E. Meyer

Nat. Commun. 2015.8

Benzophosphole P-Oxide with an Electron-Donating Group at 3-Position: Enhanced Fluorescence in Polar Solvents Reviewed

E. Yamaguchi, A. Fukazawa, Y. Kosaka, D. Yokogawa, S. Irle, S. Yamaguchi

2015.8

Atomically controlled substitutional boron-doping of graphene nanoribbons Reviewed Open Access

Shigeki Kawai, Shohei Saito, Shinichiro Osumi, Shigehiro Yamaguchi, Adam S. Foster, Peter Spijker, Ernst Meyer

NATURE COMMUNICATIONS Vol. 6 page： 8098 2015.8

Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

Boron is a unique element in terms of electron deficiency and Lewis acidity. Incorporation of boron atoms into an aromatic carbon framework offers a wide variety of functionality. However, the intrinsic instability of organoboron compounds against moisture and oxygen has delayed the development. Here, we present boron-doped graphene nanoribbons (B-GNRs) of widths of N = 7, 14 and 21 by on-surface chemical reactions with an employed organoboron precursor. The location of the boron dopant is well defined in the centre of the B-GNR, corresponding to 4.8 atom%, as programmed. The chemical reactivity of B-GNRs is probed by the adsorption of nitric oxide (NO), which is most effectively trapped by the boron sites, demonstrating the Lewis acid character. Structural properties and the chemical nature of the NO-reacted B-GNR are determined by a combination of scanning tunnelling microscopy, high-resolution atomic force microscopy with a CO tip, and density functional and classical computations.

DOI： 10.1038/ncomms9098

Open Access

Web of Science

PubMed

A Nonaromatic Thiophene-Fused Heptalene and Its Aromatic Dianion Reviewed

Hiroya Oshima, Aiko Fukazawa, Takahiro Sasamori, Shigehiro Yamaguchi

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 54 ( 26 ) page： 7636 - 7639 2015.6

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

Heptalene, a nonaromatic, bicyclic 12 -electron system with a twisted structure, is of great interest with regard to its potential Huckel aromaticity in the two-electron oxidized or reduced forms. The synthesis of thiophene-fused heptalene 5 from the reductive transannular cyclization of bisdehydro[12]annulene 4, and its solid-state structure, which was confirmed by X-ray crystallographic analysis, is presented. Chemical reduction of 5 readily generated the corresponding dianion, which was successfully isolated as [(K[2.2.2]cryptand)(+)](2)5(2-). The X-ray crystallographic analysis of the dianion revealed a shallower saddle structure for the heptalene moiety and a lesser degree of bond alternation relative to 5. (HNMR)-H-1 spectroscopy exposed the effect of a diamagnetic ring current on dianion 5(2-), which was corroborated by nucleus-independent chemical shift (NICS) calculations. These results demonstrate that the heptalene dianion, containing 14 -electrons, does indeed exhibit pronounced degrees of Huckel aromaticity.

DOI： 10.1002/anie.201501790

Web of Science

PubMed

A Red-emitting Ratiometric Fluorescent Probe Based on a Benzophosphole P-Oxide Scaffold for the Detection of Intracellular Sodium Ions Reviewed

M. Taki, H. Ogasawara, H. Osaki, A. Fukazawa, Y. Sato, K. Ogasawara, T. Higashiyama, S. Yamaguchi

Chem. Commun. Vol. 51 page： 11880-11883 2015.6

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Papers - YAMAGUCHI, Shigehiro