Faculty Profiles - YAMAGUCHI, Shigehiro

Papers - YAMAGUCHI, Shigehiro

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Donor-pi-Acceptor Type Unsymmetrical Triarylborane-Based Fluorophores: Synthesis, Fluorescence Properties, and Photostability

Masato Ito, Emi Ito, Masato Hirai, Shigehiro Yamaguchi

JOURNAL OF ORGANIC CHEMISTRY Vol. 83 ( 15 ) page： 8449 - 8456 2018.8

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

A two-step synthesis to prepare tricoordinate organoboron compounds bearing three different aryl groups has been developed. After the first aryl substitution to an aryl boronic ester took place, the intermediate species, that is, bis(diarylborinate) species, was isolated as an air- and moisture-stable solid, which allowed the second aryl substitution to carry out in a selective manner. Subsequently, a series of unsymmetrical triarylboranes possessing a sterically bulky aryl group, triarylamine moiety, and para-functionalized phenyl ring was synthesized. Not only did these triarylboranes exhibit remarkable solvent-dependent fluorescence as expected for donor it acceptor (D-pi-A) systems, they were also accompanied by profound persistence against photoirradiation especially for that bearing a 1,3,5-tri-tert-butylphenyl ring. This survey exemplifies that sufficient electronic and steric modification is key to construct photostable D-pi-A type triarylborane-based fluorophores.

DOI： 10.1021/acs.joc.8b01015

Mechanochromic Luminescent Tetrathiazolylthiophenes: Evaluating the Role of Intermolecular Interactions through Pressure and Temperature-Dependent Raman Spectroscopy

Mosca S., Milani A., Pena-Alvarez M., Yamaguchi S., Hernandez V., Ruiz Delgado M. C., Castiglioni C.

JOURNAL OF PHYSICAL CHEMISTRY C Vol. 122 ( 30 ) page： 17537 - 17543 2018.8

A Highly Photostable Near-Infrared Labeling Agent Based on a Phospha-rhodamine for Long-Term and Deep Imaging Reviewed International journal

Marek Grzybowski, Masayasu Taki, Kieko Senda, Yoshikatsu Sato, Tetsuro Ariyoshi, Yasushi Okada, Ryosuke Kawakami, Takeshi Imamura, Shigehiro Yamaguchi

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 57 ( 32 ) page： 10137 - 10141 2018.8

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

Various fluorescence microscopy techniques require bright NIR-emitting fluorophores with high chemical and photostability. Now, the significant performance improvement of phosphorus-substituted rhodamine dyes (PORs) upon substitution at the 9-position with a 2,6-dimethoxyphenyl group is reported. The thus obtained dye PREX 710 was used to stain mitochondria in living cells, which allowed long-term and three-color imaging in the vis-NIR range. Moreover, the high fluorescence longevity of PREX 710 allows tracking a dye-labeled biomolecule by single-molecule microscopy under physiological conditions. Deep imaging of blood vessels in mice brain has also been achieved using the bright NIR-emitting PREX 710-dextran conjugate.

DOI： 10.1002/anie.201804731

Electronic Properties of Substitutionally Boron-Doped Graphene Nanoribbons on a Au(111) Surface Reviewed

Eduard Carbonell-Sanroma, Aran Garcia-Lekue, Martina Corso, Guillaume Vasseur, Pedro Brandimarte, Jorge Lobo-Checa, Dimas G. de Oteyza, Jingcheng Li, Shigeki Kawai, Shohei Saito, Shigehiro Yamaguchi, J. Enrique Ortega, Daniel Sanchez-Portal, Jose Ignacio Pascual

JOURNAL OF PHYSICAL CHEMISTRY C Vol. 122 ( 28 ) page： 16092 - 16099 2018.7

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

High-quality graphene nanoribbons (GNRs) grown by on-surface synthesis strategies with atomic precision can be controllably doped by inserting heteroatoms or chemical groups in the molecular precursors. Here, we study the electronic structure of armchair GNRs substitutionally doped with di-boron moieties at the center, through a combination of scanning tunneling spectroscopy, angle resolved photoemission, and density functional theory simulations. Boron atoms appear with a small displacement toward the surface, signaling their stronger interactions with the metal. We find two boron-rich flat bands emerging as impurity states inside the GNR band gap, one of them particularly broadened after its hybridization with the gold surface states. In addition, the boron atoms shift the conduction and valence bands of the pristine GNR away from the gap edge and leave unaffected the bands above and below, which become the new frontier bands and have a negligible boron character. This is due to the selective mixing of boron states with GNR bands according to their symmetry. Our results depict that the GNR band structure can be tuned by modifying the separation between di-boron moieties.

DOI： 10.1021/acs.jpcc.8b03748

A planarized B-phenyldibenzoborepin: impact of structural constraint on its electronic properties and Lewis acidity

Naoki Ando, Tomokatsu Kushida, Shigehiro Yamaguchi

CHEMICAL COMMUNICATIONS Vol. 54 ( 41 ) page： 5213 - 5216 2018.5

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

A B-phenyldibenzo[b,f]borepin planarized with two methylene bridges was synthesized. The structural constraint on the B-phenyl group resulted in a bathochromic shift of the absorption and fluorescence properties as well as enhanced Lewis acidity. A donor--acceptor type derivative based on this scaffold exhibited intense fluorescence irrespective of the solvent polarity.

DOI： 10.1039/c8cc02837k

A far-red emitting fluorescent probe for cytosolic Ca2+ion based on phospha-fluorescein scaffold

Ogasawara Hiroaki, Taki Masayasu, Sato Yoshikatsu, Yamaguchi Shigehiro

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 255 2018.3

Near infrared two-photon-excited and -emissive dyes based on a strapped excited-state intramolecular proton-transfer (ESIPT) scaffold Reviewed

Naoya Suzuki, Kayo Suda, Daisuke Yokogawa, Hirotaka Kitoh-Nishioka, Stephan Irle, Akihiro Ando, Luis M. G. Abegao, Kenji Kamada, Aiko Fukazawa, Shigehiro Yamaguchi

CHEMICAL SCIENCE Vol. 9 ( 10 ) page： 2666 - 2673 2018.3

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

Fluorophores that can undergo excited-state intramolecular proton transfer (ESIPT) represent promising scaffolds for the design of compounds that show red-shifted fluorescence. Herein, we disclose new near infrared-emissive materials based on a dialkylamine-strapped 2,5-dithienylpyrrole as an ESIPT scaffold. The introduction of electron-accepting units to the terminal positions of this scaffold generates acceptor-pi-donor-pi-acceptor (A-pi-D-pi-A) type pi-conjugated compounds. Following the ESIPT, the electron-donating ability of the core scaffold increases, which results in a substantially red-shifted emission in the NIR region, while increasing the oscillator strength. The electron-accepting units play a vital role to achieve intense and red-shifted emission from the ESIPT state. The strapped dialkylamine chain that forms an intramolecular hydrogen bond is also essential to induce the ESIPT. Moreover, an extended A-pi-D-pi-A skeleton enables two-photon excitation with the NIR light. One of the derivatives that satisfy these features, i.e., borylethenyl-substituted 5, exhibited an intense NIR emission in polar solvents such as acetone (lambda(em) = 708 nm, phi(F) = 0.55) with a strong two-photon-absorption band in the NIR region.

DOI： 10.1039/c8sc00066b

Seeded Polymerization through the Interplay of Folding and Aggregation of an Amino-Acid-based Diamide

Soichiro Ogi, Kentaro Matsumoto, Shigehiro Yamaguchi

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 57 ( 9 ) page： 2339 - 2343 2018.2

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

Amino acid based diamides are widely used as a substructure in supramolecular polymers and are also key components of polypeptides that help to understand protein folding. The interplay of folding and aggregation of a diamide was used to achieve seed-initiated supramolecular polymerization. For that purpose, a pyrene-substituted diamide was synthesized in which pyrene is used as a tracer to monitor the supramolecular polymerization. Thermodynamics and time-dependent studies revealed that the folding of the diamide moiety, via the formation of intramolecular hydrogen bonds, effectively prevents a spontaneous nucleation that leads to supramolecular polymerization. Under such out-of-equilibrium conditions, the addition of seeds successfully initiates the supramolecular polymerization. These results demonstrate the utility of such amino acid based diamides in programmable supramolecular polymerizations.

DOI： 10.1002/anie.201712119

A far-red fluorescent probe based on a phospha-fluorescein scaffold for cytosolic calcium imaging

Hiroaki Ogasawara, Marek Grzybowski, Riho Hosokawa, Yoshikatsu Sato, Masayasu Taki, Shigehiro Yamaguchi

CHEMICAL COMMUNICATIONS Vol. 54 ( 3 ) page： 299 - 302 2018.1

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

The far-red emissive fluorescent probe CaPF-1 based on a phospha-fluorescein scaffold enables the detection of cytosolic calcium ions in living cells. The probe can be excited in the red region (lambda(abs) = 636 nm) and exhibits a sufficiently high fluorescence turn-on response in the far-red region (lambda(em) = 663 nm) upon complexation with calcium ions. The hydrophilic and anionic characteristics of this phospha-fluorescein fluorophore allowed the cytosolic localization of CaPF-1. Moreover, it was possible to visualize histamineinduced calcium oscillation in HeLa cells using CaPF-1.

DOI： 10.1039/c7cc07344e

Antiaromatic Dithieno-1,2-dihydro-1,2-diborin Splits Diatomic Hydrogen

Takafumi Araki, Masato Hirai, Atsushi Wakamiya, Warren E. Piers, Shigehiro Yamaguchi

CHEMISTRY LETTERS Vol. 46 ( 12 ) page： 1714 - 1717 2017.12

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

B,B-Dimesityl-substituted dithieno-1,2-dihydro-1,2-diborin was synthesized and its properties and reactivity were studied. Owing to the noticeably electron-deficient and antiaromatic character of the 1,2-dihydro-1,2-diborin ring, this compound was found to homolytically cleave diatomic hydrogen (H-2) gas at ambient temperature under 1 atm to afford a hydrogen-bridged bis(borane). This reaction was accompanied by a dramatic color change from dark green to yellow in addition to a turn-on fluorescence response.

DOI： 10.1246/cl.170812

Phosphole P-Oxide-Containing pi-Electron Materials: Synthesis and Applications in Fluorescence Imaging

Yamaguchi Shigehiro, Fukazawa Aiko, Taki Masayasu

JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN Vol. 75 ( 11 ) page： 1179-1187 2017.11

Structural Monitoring of the Onset of Excited-State Aromaticity in a Liquid Crystal Phase

Masaki Hada, Shohei Saito, Sei'ichi Tanaka, Ryuma Sato, Masahiko Yoshimura, Kazuhiro Mouri, Kyohei Matsuo, Shigehiro Yamaguchi, Mitsuo Hara, Yasuhiko Hayashi, Fynn Roehricht, Rainer Herges, Yasuteru Shigeta, Ken Onda, R. J. Dwayne Miller

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Vol. 139 ( 44 ) page： 15792 - 15800 2017.11

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

Aromaticity of photoexcited molecules is an important concept in organic chemistry. Its theory, Baird's rule for triplet aromaticity since 1972 gives the rationale of photoinduced conformational changes and photochemical reactivities of cyclic pi-conjugated systems. However, it is still challenging to monitor the dynamic structural change induced by the excited-state aromaticity, particularly in condensed materials. Here we report direct structural observation of a molecular motion and a subsequent packing deformation accompanied by the excited-state aromaticity. Photoactive liquid crystal (LC) molecules featuring a pi-expanded cyclooctatetraene core unit are orientationally ordered but loosely packed in a columnar LC phase, and therefore a photoinduced conformational planarization by the excited-state aromaticity has been successfully observed by time-resolved electron diffractometry and vibrational spectroscopy. The structural change took place in the vicinity of excited molecules, producing a twisted stacking structure. A nanoscale torque driven by the excited-state aromaticity can be used as the working mechanism of new photoresponsive materials.

DOI： 10.1021/jacs.7b08021

An Expedient Procedure for the Synthesis of Benzo[4,5]silolo[2,3-b]thiophenes and Related Systems

Susanne Baehr, Hiroaki Ogasawara, Shigehiro Yamaguchi, Martin Oestreich

ORGANOMETALLICS Vol. 36 ( 20 ) page： 4013 - 4019 2017.10

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

The straightforward assembly of various thiophene-fused benzosiloles is accomplished by 2-fold metalation of benzo[b]thiophenes substituted at C3 with ortho-brominated aryl groups followed by electrophilic substitution with dichlorosilanes. The method relies on the innate acidity of the C(sp(2))-H bond at C2 of benzo[b]thiophenes and the halogen-metal exchange of the proximal C(sp(2))-Br bond. The related indole- and benzofuran-annulated systems are also accessible, but these siloles are chemically less stable. An example of a thiophene-fused benzogermole is included as well.

DOI： 10.1021/acs.organomet.7b00619

Boron-Stabilized Planar Neutral pi-Radicals with Well-Balanced Ambipolar Charge-Transport Properties

Tomokatsu Kushida, Shusuke Shirai, Naoki Ando, Toshihiro Okamoto, Hiroyuki Ishi, Hiroyuki Matsui, Masakazu Yamagishi, Takafumi Uemura, Junto Tsurumi, Shun Watanabe, Jun Takeya, Shigehiro Yamaguchi

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Vol. 139 ( 41 ) page： 14336 - 14339 2017.10

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

Organic neutral pi-monoradicals are promising semiconductors with balanced ambipolar carrier transport abilities, which arise from virtually identical spatial distribution of their singly occupied and unoccupied molecular orbitals, SOMO(alpha) and SOMO(beta), respectively. Herein, we disclose a boron-stabilized triphenylmethyl radical that shows outstanding thermal stability and resistance toward atmospheric conditions due to the substantial spin delocalization. The radical is used to fabricate organic Mott-insulator transistors that operate at room temperature, wherein the radical exhibits well-balanced ambipolar carrier transport properties.

DOI： 10.1021/jacs.7b05471

Structural Monitoring of the Onset of Excited-State Aromaticity in a Liquid Crystal Phase Reviewed

Hada, Masaki, Saito, Shohei, Tanaka, Sei'ichi, Sato, Ryuma, Yoshimura, Masahiko, Mouri, Kazuhiro, Matsuo, Kyohei, Yamaguchi, Shigehiro, Hara, Mitsuo, Hayashi, Yasuhiko, Röhricht, Fynn, Herges, Rainer, Shigeta, Yasuteru, Onda, Ken, Miller, R J Dwayne

Journal of the American Chemical Society Vol. 139 page： 15792 - 15800 2017.10

Photochemical Intramolecular C-H Addition of Dimesityl(hetero)arylboranes through a [1,6]-Sigmatropic Rearrangement

Naoki Ando, Aiko Fukazawa, Tomokatsu Kushida, Yoshihito Shiota, Shuhei Itoyama, Kazunari Yoshizawa, Yasunori Matsui, Yutaro Kuramoto, Hiroshi Ikeda, Shigehiro Yamaguchi

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 56 ( 40 ) page： 12210 - 12214 2017.9

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

A new reaction mode for triarylboranes under photochemical conditions was discovered. Photoirradiation of dimesitylboryl-substituted (hetero)arenes produced spirocyclic boraindanes, where one of the C-H bonds in the ortho-methyl groups of the mesityl substituents was formally added in a syn fashion to a C-C double bond of the (hetero)aryl group. Quantum chemical calculations and laser flash photolysis measurements indicated that the reaction proceeds through a [1,6]-sigmatropic rearrangement. This behavior is reminiscent of the photochemical reaction mode of arylalkenylketones, thus demonstrating the isosteric relation between tricoordinate organoboron compounds and the corresponding pseudo-carbocationic species in terms of pericyclic reactions. Despite the disrupted -conjugation, the resulting spirocyclic boraindanes exhibited a characteristic absorption band at relatively long wavelengths (=370400 nm).

DOI： 10.1002/anie.201706929

Selective Conversion of P=O-Bridged Rhodamines into P=O-Rhodols: Solvatochromic Near-Infrared Fluorophores

Marek Grzybowski, Masayasu Taki, Shigehiro Yamaguchi

CHEMISTRY-A EUROPEAN JOURNAL Vol. 23 ( 53 ) page： 13028 - 13032 2017.9

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

The substitution of an oxygen atom in rhodols with a phosphine oxide (P=O) moiety affords P=O-bridged rhodols as a new type of near-infrared (NIR) fluorophore. This compound class can be readily accessed upon exposure of the corresponding rhodamines to aqueous basic conditions. The electron-withdrawing effect of the P=O group facilitates the hydrolytic deamination, and, moreover, prolonged exposure to aqueous basic conditions generates P=O-bridged fluoresceins, that is, a series of three P=O-bridged xanthene dyes is available in one simple operation. The P=O-bridged rhodols show significant bathochromic shifts of the longest-wavelength absorption maximum (Delta lambda = 125 nm; > 3600 cm(-1)) upon changing the solvent from toluene to water, whereas the emission is shifted less drastically (Delta lambda = 70 nm; 1600 cm @ 1). The hydrogen bonding between the P=O and C=O groups with protic solvents results in substantial stabilization of the LUMO level, which is responsible for the solvatochromism.

DOI： 10.1002/chem.201703456

Photochemical Intramolecular C−H Addition of Dimesityl(hetero)arylboranes through a [1,6]-Sigmatropic Rearrangement Reviewed

Naoki Ando, Aiko Fukazawa, Tomokatsu Kushida, Yoshihito Shiota, Shuhei Itoyama, Kazunari Yoshizawa, Yasunori Matsui, Yutaro Kuramoto, Hiroshi Ikeda, Shigehiro Yamaguchi

Angewandte Chemie Vol. 129 ( 40 ) page： 12378 2017.9

Synthesis of seminaphtho-phospha-fluorescein dyes based on the consecutive arylation of aryldichlorophosphines

Aiko Fukazawa, Junichi Usuba, Raul A. Adler, Shigehiro Yamaguchi

CHEMICAL COMMUNICATIONS Vol. 53 ( 61 ) page： 8565 - 8568 2017.8

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

Seminaphtho-phospha-fluorescein (SNAPF), a phosphine-oxide-containing unsymmetric fluorescein dye, was synthesized based on the consecutive arylation of PhPCl2, followed by Friedel-Crafts cyclization. The resulting SNAPF exhibited several attractive photo-physical properties including an intense fluorescence in the NIR region and a large Stokes shift.

DOI： 10.1039/c7cc04323f

Super-Photostable Phosphole-Based Dye for Multiple-Acquisition Stimulated Emission Depletion Imaging

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

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Vol. 139 ( 30 ) page： 10374 - 10381 2017.8

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

As stimulated emission depletion (STED) microscopy can provide structural details of cells with an optical resolution beyond the diffraction limit, it has become an indispensable tool in cell biology. However, the intense STED laser beam usually causes rapid photobleaching of the employed fluorescent dyes, which significantly limits the utility of STED microscopy from a practical perspective. Herein we report a new design of super-photostable dye, PhoxBright 430 (PB430), comprising a fully ring-fused pi-conjugated skeleton with an electron-accepting phosphole pi-oxide unit. We previously developed a super-photostable dye C-Naphox by combining the phosphole unit with an electron-donating triphenylamine moiety. In PB430, removal of the amino group alters the transition type from intramolecular charge transfer character to pi-pi* transition character, which gives rise to intense fluorescence insensitive to molecular environment in terms of fluorescence colors and intensity, and bright fluorescence even in aqueous media. PB430 also furnishes high solubility in water, and is capable of labeling proteins with maintaining high fluorescence quantum yields. This dye exhibits outstanding resistance to photoirradiation even under the STED conditions and allows continuous acquisition of STED images. Indeed, using a PB430-conjugated antibody, we succeed in attaining a 3-D reconstruction of super-resolution STED images as well as photostability-based multicolor STED imaging of fluorescently labeled cytoskeletal structures.

DOI： 10.1021/jacs.7b04418

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