Faculty Profiles - YAMAGUCHI, Shigehiro

Secretion of mitochondrial DNA via exosomes promotes inflammation in Behçet's syndrome Reviewed Open Access

Konaka, H; Kato, Y; Hirano, T; Tsujimoto, K; Park, J; Koba, T; Aoki, W; Matsuzaki, Y; Taki, M; Koyama, S; Itotagawa, E; Jo, T; Hirayama, T; Kawai, T; Ishii, KJ; Ueda, M; Yamaguchi, S; Akira, S; Morita, T; Maeda, Y; Nishide, M; Nishida, S; Shima, Y; Narazaki, M; Takamatsu, H; Kumanogoh, A

EMBO JOURNAL Vol. 42 ( 20 ) page： e112573 2023.10

A Kinetically Stabilized Nitrogen‐Doped Triangulene Cation: Stable and NIR Fluorescent Diradical Cation with Triplet Ground State Reviewed Open Access

Shinobu Arikawa, Akihiro Shimizu, Daisuke Shiomi, Kazunobu Sato, Takeji Takui, Hikaru Sotome, Hiroshi Miyasaka, Masahito Murai, Shigehiro Yamaguchi, Ryo Shintani

Angewandte Chemie International Edition Vol. 62 ( 29 ) page： e202302714 2023.7

Photodissociative Modules that Control Dual-Emission Properties in Donor-pi-Acceptor Organoborane Fluorophores Reviewed Open Access

Midori Kawashiro, Tatsuya Mori, Masato Ito, Naoki Ando, Shigehiro Yamaguchi

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 62 ( 26 ) page： e202303725 2023.6

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

Donor-pi-acceptor fluorophores that consist of an electron-donating amino group and an electron-accepting triarylborane moiety generally exhibit substantial solvatochromism in their fluorescence while retaining high fluorescence quantum yields even in polar media. Herein, we report a new family of this compound class, which bears ortho-P(=X)R-2-substituted phenyl groups (X=O or S) as a photodissociative module. The P=X moiety that intramolecularly coordinates to the boron atom undergoes dissociation in the excited state, giving rise to dual emission from the corresponding tetra- and tricoordinate boron species. The susceptibility of the systems to photodissociation depends on the coordination ability of the P=O and P=S moieties, whereby the latter facilitates dissociation. The intensity ratios of the dual emission bands are sensitive to environmental parameters, including temperature, solution polarity, and the viscosity of the medium. Moreover, precise tuning of the P(=X)R-2 group and the electron-donating amino moiety led to single-molecule white emission in solution.

DOI： 10.1002/anie.202303725

A Synthetic Strategy for Multi-Functionalized Phospharhodamines via Catalytic P-Arylation Reviewed

Yuichi Asada, Masayasu Taki, Shigehiro Yamaguchi

Bulletin of the Chemical Society of Japan Vol. 96 ( 6 ) page： 601 - 606 2023.6

Language：English Publishing type：Research paper (scientific journal)

The visualization of complex biological events in living cells is highly reliant on the development of sophisticated fluorescent probes with multiple functions. Herein, we report a general synthetic strategy for the synthesis of near-infraredemissive phospharhodamines (PORs) bearing various types of aryl groups on their bridging phosphorus atoms. This versatile approach utilizes a Ni-catalyzed P-arylation that allows for the design of POR-based multi-functionalized fluorescent probes. We found that PORs substituted with an aminophenyl group exhibited pH-responsive fluorescence intensity, where photo-induced electron transfer occurs to quench the fluorescence. The combination of our new approach with conventional modification at the 9-position of the xanthene skeleton facilitates the development of multi-functionalized fluorescent probes. As one demonstration of this method, we synthesized a fluorescence probe that can selectively visualize the lysosomes that result from endosomal maturation.

DOI： 10.1246/bcsj.20230082

Scopus

Flattened 1D fragments of fullerene C60 that exhibit robustness toward multi-electron reduction Reviewed Open Access

Masahiro Hayakawa, Naoyuki Sunayama, Shu I. Takagi, Yu Matsuo, Asuka Tamaki, Shigehiro Yamaguchi, Shu Seki, Aiko Fukazawa

Nature Communications Vol. 14 ( 1 ) page： 2741 2023.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

Fullerenes are compelling molecular materials owing to their exceptional robustness toward multi-electron reduction. Although scientists have attempted to address this feature by synthesizing various fragment molecules, the origin of this electron affinity remains unclear. Several structural factors have been suggested, including high symmetry, pyramidalized carbon atoms, and five-membered ring substructures. To elucidate the role of the five-membered ring substructures without the influence of high symmetry and pyramidalized carbon atoms, we herein report the synthesis and electron-accepting properties of oligo(biindenylidene)s, a flattened one-dimensional fragment of fullerene C<sub>60</sub>. Electrochemical studies corroborated that oligo(biindenylidene)s can accept electrons up to equal to the number of five-membered rings in their main chains. Moreover, ultraviolet/visible/near-infrared absorption spectroscopy revealed that oligo(biindenylidene)s exhibit enhanced absorption covering the entire visible region relative to C<sub>60</sub>. These results highlight the significance of the pentagonal substructure for attaining stability toward multi-electron reduction and provide a strategy for the molecular design of electron-accepting π-conjugated hydrocarbons even without electron-withdrawing groups.

DOI： 10.1038/s41467-023-38300-3

Other Link： https://www.nature.com/articles/s41467-023-38300-3

1,6-Disila[4.4.4]propellane Revisited–Part 1: Improved Synthesis by a Mechanistically Logical Fluorosilane Route and Its Structural Aspects Including Linear Stacking along the Si–Si Bond in the Crystalline State Reviewed

1. S. Kobayashi, T. Sasamori, Y. Nakajima, Y. Minami, K. Iizuka, T. Saeki, A. Toshimitsu, H. Tsuji, S. Yamaguchi, A. Fukazawa, T. Kushida, D. Hashizume, K. Tamao

Bull. Chem. Soc. Jpn. Vol. 99 page： uoaf119 2023.1

Manipulation of Spin Polarization in Boron-Substituted Graphene Nanoribbons Invited Reviewed International coauthorship Open Access

Kewei Sun, Orlando J. Silveira, Shohei Saito, Keisuke Sagisaka, Shigehiro Yamaguchi, Adam S. Foster, Shigeki Kawai

ACS NANO Vol. 16 ( 7 ) page： 11244 - 11250 2022.6

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

The design of magnetic topological states due to spin polarization in an extended pi carbon system has great potential in spintronics application. Although magnetic zigzag edges in graphene nanoribbons (GNRs) have been investigated earlier, real-space observation and manipulation of spin polarization in a heteroatom substituted system remains challenging. Here, we investigate a zero-bias peak at a boron site embedded at the center of an armchair-type GNR on a AuSiX/Au(111) surface with a combination of low-temperature scanning tunneling microscopy/spectroscopy and density functional theory calculations. After the tip-induced removal of a Si atom connected to two adjacent boron atoms, a clear Kondo resonance peak appeared and was further split by an applied magnetic field of 12 T. This magnetic state can be relayed along the longitudinal axis of the GNR by sequential removal of Si atoms.

DOI： 10.1021/acsnano.2c04563

Fluorescent Organic pi-Radicals Stabilized with Boron: Featuring a SOMO-LUMO Electronic Transition Reviewed Open Access

Masato Ito, Shusuke Shirai, Yongfa Xie, Tomokatsu Kushida, Naoki Ando, Hiroki Soutome, Kazuhiro J. Fujimoto, Takeshi Yanai, Kenichi Tabata, Yasuo Miyata, Hiroshi Kita, Shigehiro Yamaguchi

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 61 ( 25 ) page： e202201965 2022.6

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

We report on the fluorescence properties of a new class of emissive and stable pi-radicals that contain a boron atom at a position distant from the radical center. A fully planarized derivative exhibited an intense red fluorescence with high fluorescence quantum yields (Phi(F) > 0.67) even in polar solvents. To elucidate the origin of this phenomenon, we synthesized another boron-stabilized radical that contains a bulky aryl group on the boron atom. A comparison of these derivatives, as well as with conventional donor-rr-acceptor (D-pi-A)-type emissive pi-radicals, unveiled several characteristic features in their photophysical properties. A theoretical analysis revealed that the SOMO-LUMO electronic transition generates an emissive D-1 state. Unlike conventional D-pi-A-type pi-radicals, this state does not undergo significant structural relaxation. The boron-stabilized pi-radicals demonstrated promising potential for organic light-emitting diodes as an emitting material.

DOI： 10.1002/anie.202201965

Late-stage modification of π-electron systems based on asymmetric oxidation of a medium-sized sulfur-containing ring Reviewed

Masahiro Hayakawa, Satoshi Horike, Yuh Hijikata, Kosuke Yasui, Shigehiro Yamaguchi, Aiko Fukazawa

Chemical Communications Vol. 58 ( 15 ) page： 2548 - 2551 2022.2

Fully fused boron-doped polycyclic aromatic hydrocarbons: their synthesis, structure-property relationships, and self-assembly behavior in aqueous media Reviewed Open Access

Hiroki Narita, Heekyoung Choi, Masato Ito, Naoki Ando, Soichiro Ogi, Shigehiro Yamaguchi

CHEMICAL SCIENCE Vol. 13 ( 5 ) page： 1484 - 1491 2022.2

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

Planarized triarylboranes are attracting increasing attention not only as models of boron-doped graphenes, but also as promising materials for organic optoelectronics. In particular, polycyclic aromatic hydrocarbon (PAH) skeletons with embedded boron atom(s) in the inner positions are of importance in light of their high chemical stability and pi-stacking ability derived from their planar geometries. Herein, we disclose a robust synthesis of such fully fused boron-doped PAHs and their self-assembly behavior in aqueous media to explore their potential utility in biological applications. The synthesis using in situ-generated planar diarylboranes as a key precursor afforded a series of fully fused boron-doped PAHs, even including an amphiphilic derivative with hydrophilic side chains. These compounds exhibited red emission in solution, and slight structural modification resulted in increased fluorescence brightness. While these compounds showed relatively low Lewis acidity compared to their partially ring-fused counterparts, their Lewis acidities were slightly increased in polar solvents compared to those in nonpolar solvents. In addition, their B-N Lewis acid-base adducts, even those with a strong, charge-neutral Lewis base such as N,N-dimethylaminopyridine (DMAP), exhibited photo-dissociation behavior in the excited state. The amphiphilic derivative showed significant spectral changes with increased water content in DMSO/H2O mixed media and formed sheet-like aggregates. The disassembly and assembly processes of the aggregates were externally controlled by the addition of DMAP and an acid, accompanied by a change in the fluorescence intensity.

DOI： 10.1039/d1sc06710a

Bridging pico-to-nanonewtons with a ratiometric force probe for monitoring nanoscale polymer physics before damage. Reviewed International journal Open Access

Ryota Kotani, Soichi Yokoyama, Shunpei Nobusue, Shigehiro Yamaguchi, Atsuhiro Osuka, Hiroshi Yabu, Shohei Saito

Nature communications Vol. 13 ( 1 ) page： 303 - 303 2022.1

Language：English Publishing type：Research paper (scientific journal)

Understanding the transmission of nanoscale forces in the pico-to-nanonewton range is important in polymer physics. While physical approaches have limitations in analyzing the local force distribution in condensed environments, chemical analysis using force probes is promising. However, there are stringent requirements for probing the local forces generated before structural damage. The magnitude of those forces corresponds to the range below covalent bond scission (from 200 pN to several nN) and above thermal fluctuation (several pN). Here, we report a conformationally flexible dual-fluorescence force probe with a theoretically estimated threshold of approximately 100 pN. This probe enables ratiometric analysis of the distribution of local forces in a stretched polymer chain network. Without changing the intrinsic properties of the polymer, the force distribution was reversibly monitored in real time. Chemical control of the probe location demonstrated that the local stress concentration is twice as biased at crosslinkers than at main chains, particularly in a strain-hardening region. Due to the high sensitivity, the percentage of the stressed force probes was estimated to be more than 1000 times higher than the activation rate of a conventional mechanophore.

DOI： 10.1038/s41467-022-27972-y

Extended π-Electron Delocalization in Quinoid-Based Conjugated Polymers Boosts Intrachain Charge Carrier Transport

Tsubasa Mikie, Masahiro Hayakawa, Kenta Okamoto, Keitaro Iguchi, Shuhei Yashiro, Tomoyuki Koganezawa, Masatomo Sumiya, Hiroyuki Ishii, Shigehiro Yamaguchi, Aiko Fukazawa, Itaru Osaka

Chemistry of Materials Vol. 33 ( 21 ) page： 8183 - 8193 2021.11

Electron-Deficient Heteroacenes that Contain Two Boron Atoms: Near-Infrared Fluorescence Based on a Push-Pull Effect** Reviewed

Masato Ito, Mika Sakai, Naoki Ando, Shigehiro Yamaguchi

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Vol. 60 ( 40 ) page： 21853 - 21859 2021.9

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

Electron-deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of silicon-bridged precursors. X-ray crystallographic analysis revealed quinoidal structures, which give rise to two-step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near-infrared (NIR) region. These properties originate from the push-pull effect along the long axis of the molecule derived from the electron-donating ether moieties and the electron-accepting boron moieties. Of particular note is the NIR emission of the thienothiophene-centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm(-1) in cyclohexane. A Franck-Condon analysis revealed the crucial role of the sterically less-hindered thienothiophene spacer in achieving this sharp emission band.

DOI： 10.1002/anie.202106642

Donor-acceptor-acceptor-type near-infrared fluorophores that contain dithienophosphole oxide and boryl groups: effect of the boryl group on the nonradiative decay dagger Reviewed Open Access

Yoshiaki Sugihara, Naoto Inai, Masayasu Taki, Thomas Baumgartner, Ryosuke Kawakami, Takashi Saitou, Takeshi Imamura, Takeshi Yanai, Shigehiro Yamaguchi

CHEMICAL SCIENCE Vol. 12 ( 18 ) page： 6333 - 6341 2021.5

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

The use of donor-pi-acceptor (D-pi-A) skeletons is an effective strategy for the design of fluorophores with red-shifted emission. In particular, the use of amino and boryl moieties as the electron-donating and -accepting groups, respectively, can produce dyes that exhibit high fluorescence and solvatochromism. Herein, we introduce a dithienophosphole P-oxide scaffold as an acceptor-spacer to produce a boryl- and amino-substituted donor-acceptor-acceptor (D-A-A) pi-system. The thus obtained fluorophores exhibit emission in the near-infrared (NIR) region, while maintaining high fluorescence quantum yields even in polar solvents (e.g. lambda(em) = 704 nm and phi(F) = 0.69 in CH3CN). A comparison of these compounds with their formyl- or cyano-substituted counterparts demonstrated the importance of the boryl group for generating intense emission. The differences among these electron-accepting substituents were examined in detail using theoretical calculations, which revealed the crucial role of the boryl group in lowering the nonradiative decay rate constant by decreasing the non-adiabatic coupling in the internal conversion process. The D-A-A framework was further fine-tuned to improve the photostability. One of these D-A-A dyes was successfully used in bioimaging to visualize the blood vessels of Japanese medaka larvae and mouse brain.

DOI： 10.1039/d1sc00827g