Faculty Profiles - YOSHIDA Takefumi

Published Papers - YOSHIDA Takefumi

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Ln-Pt Electron Polarization Affected Slow Magnetic Relaxation with Heterometallic Er, Ho-Pt Complexes

Takefumi Yoshida, David C. Izuogu, Hai-Tao Zhang, Goulven Cosquer, Hitoshi Abe, Wolfgang Wernsdorfer, Brian K. Breedlove, Masahiro Yamashita

Dalton Trans. 48 7144 - 7149 2019 [Refereed] [Invited]

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Observation of charge bistability in quasi-one-dimensional halogen-bridged palladium complexes by X-ray absorption spectroscopy

Takefumi Yoshida, Shinya Takaishi, Shohei Kumagai, Hiroaki Iguchi, Rasel Mian Mohamad, Masahiro Yamashita （Part： Lead author )

Dalton Trans. 48 11628 - 11631 2019 [Refereed]

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Porous Molecular Conductor: Electrochemical Fabrication of Through-Space Conduction Pathways among Linear Coordination Polymers

L. Qu, H. Iguchi, S. Takaishi, F. Habib, C. F. Leong, D. M.D'Alessandro, T. Yoshida, H. Abe, E. Nishibori, M. Yamashita

J. Am. Chem. Soc. 141 6802 - 6806 2019 [Refereed]

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Synchrotron-radiation-based Mössbauer Absorption Spectroscopy with High Resonant Energy Nuclides

R. Masuda, K. Kusada, T. Yoshida, S. Michimura, Y. Kobayashi, S. Kitao, H. Tajima, T. Mitsui, H. Kobayashi, H. Kitagawa, M. Seto

Hyperfine Interactions ( SPRINGER INTERNATIONAL PUBLISHING AG ) 240 ( 1 ) 120 2019 [Refereed]

We successfully observed the synchrotron-radiation-based Mossbauer absorption spectra with Gd-158 and Ru-99. Their nuclear resonant energies were 79.5 keV and 89.6 keV, respectively, and they are factually the highest energy which energy region synchrotron radiation covers with sufficient intensity as the incident X-rays for Mossbauer spectroscopy. Although the low recoilless fraction owing to these high resonant energy, Mossbauer energy spectra of GdPd3 to (Gd2O3)-Gd-158 and fcc-Ru nanoparticles to bulk hcp-Ru-99 metal were obtained with natural samples of the former compounds with sufficient amount, because of the high transparency of these high energy X-rays(to electronic scattering). In spite of large statistical errors, we can evaluate the hyperfine parameters when the spectrum includes simple 1-site profile. Ru-99 and Gd-158 SR-based Mossbauer absorption spectra of various complex materials including somewhat complex structures will be available with the improvements to the measurement system; More detector elements for larger solid angle subtended to the scatterer sample will yields more counting rates and improvement higher recoilless fraction by arranging more appropriate chemical specimen as the scatterer yields deeper absorption profile.

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Slow magnetic relaxation in a Tb(III)-based coordination polymer

Takefumi Yoshida, Yemineni S. L. V. Narayana, Hitoshi Abe, Masayoshi Higuchi （Part： Lead author )

DALTON TRANSACTIONS ( ROYAL SOC CHEMISTRY ) 47 ( 45 ) 16066 - 16071 2018.12 [Refereed]

A Tb(III)-based coordination polymer (polyTb) was synthesized by complexation of Tb(NO3)(3)center dot(6H(2)O) and 4',4 ''''-[1,1'-biphenyl]-4,4'-diylbis[6,6 ''-bis(ethoxycarbonyl)2':6',2 ''-terpyridine](L). The polymer structure was determined by Job's plots, DFT calculation, and X-ray absorption fine structure (XAFS) measurement. Job's plots indicated that the mole ratio (Tb ion:L) is 1:1. The optimized model structures suggested a La model: the LaN6 center dot center dot center dot(O=C)(2) model. The bond distances of La-O and La-N are similar to 2.80 angstrom and 2.60 angstrom, respectively. The EXAFS fitting indicated that the bond distances of Tb-O and Tb-N are 2.65 angstrom and 2.95 angstrom, respectively. polyTb shows field-induced magnetic relaxation in the solid and solution state. The luminescence of polyTb, originating from an f-f transition, was observed (phi = 6.9%). polyTb formed a porous structure on a Si substrate, whereas a fibrous complex structure was formed on glass. polyTb chains are orientated on glass, which were determined by XRD.

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Modulation of a coordination structure in a europium(III)-based metallo-supramolecular polymer for high proton conduction

Yemineni S. L. V. Narayana, Chanchal Chakraborty, Utpal Rana, Yoshikazu Ninomiya, Takefumi Yoshida, Masayoshi Higuchi

RSC ADVANCES ( ROYAL SOC CHEMISTRY ) 8 ( 65 ) 37193 - 37199 2018 [Refereed]

Developing high proton conducting solid materials is significant in the field of fuel cells. A europium(III)based metallo-supramolecular polymer with uncoordinated carboxylic acids (PolyEu-H) was successfully synthesized by modifying the synthesis conditions. The proton conductivity was enhanced with increasing the relative humidity (RH) from 30 to 95% RH. PolyEu-H showed about 104 times higher proton conductivity than the polymer with coordinated carboxylic acids (PolyEu) and about 400 times higher than the polymer without carboxylic acids (PolyEu-2). The proton conductivity of PolyEu-H reached 4.45 x 10(-2) S cm(-1) at 95% RH and 25 degrees C and 5.6 x 10(-2) S cm(-1) at 75 degrees C. The activation energy, Ea was ultralow (0.04 eV), which indicates proton conduction based on the Grotthuss mechanism. The results indicate that efficient proton conduction occurs through proton channels formed by moisture in PolyEu-H.

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Diversity in Design of Electrochromic Devices with Metallo-Supramolecular Polymer: Multi-Patterned and Tube-Shaped Displays

Takefumi Yoshida, Masayoshi Higuchi （Part： Lead author )

JOURNAL OF PHOTOPOLYMER SCIENCE AND TECHNOLOGY ( TECHNICAL ASSOC PHOTOPOLYMERS,JAPAN ) 31 ( 3 ) 343 - 347 2018 [Refereed]

As newly designed electrochromic devices (ECDs), we fabricated a multi-patterned display (MPD) and a tube-shaped display (TSD) with Fe(II)-based metallo-supramolecular polymer (polyFe) and/or Ru(II)-based polymer (polyRu). The MPD was fabricated by staking three independent ECDs. The device thickness was less than 5 mm using both-sides-coated ITO glasses. The MPD presented eight different images with high contrast and fast response. The bleaching and coloring times (T-b and T-c) were 1.7 and 2.0 s at 500 nm, in which the absorption attributed to polyRu appears, respectively, and 3.6 and 1.8 s at 600 nm, in which the absorption attributed to polyFe appears, respectively. The TSD was successfully fabricated using two flexible ITO-PET films and two tube-shaped glasses. The TSD also showed good electrochromic behavior (T-b: 22 s and T-c: 3.6 s). These results guarantee the achievement of the further application for new design of architecture or appliance.

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Slow Magnetic Relaxation in a Palladium‐Gadolinium Complex Induced by Electron Density Donation from the Palladium Ion

David Chukwuma Izougu, Takefumi Yoshida, Haitao Zhang, Goulven Cosquer, Keiichi Katoh, Shuhei Ogata, Miki Hasekawa, Hiroyuki Nojiri, Marko Damjanović, Wolfgang Wernsdorfer, Tomoya Uruga, Toshiaki Ina, Brian K. Breedlove, Masahiro Yamashita （Part： Lead author,　Corresponding author )

Chem. Eur. J. 24 9285 - 9294 2018 [Refereed]

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Multiple Magnetic Relaxation Pathways and Dual-Emission Modulated by a Heterometallic Tb-Pt Bonding Environment

Takefumi Yoshida, David Chukwuma Izougu, Daichi Iwasawa, Shuhei Ogata, Miki Hasegawa, Brian K. Breedlove, Goulven Cosquer, Wolfgang Wernsdorfer, Masahiro Yamashita （Part： Lead author,　Corresponding author )

CHEMISTRY-A EUROPEAN JOURNAL ( WILEY-V C H VERLAG GMBH ) 23 ( 44 ) 10527 - 10531 2017.08 [Refereed]

A heterometallic Tb-Pt complex, [Tb2Pt3(SAc)(12)(H2O)(2)] (SAc = thioacetate), was synthesized. Dual emission was modulated by the presence of a heterometallic Tb-Pt bonding environment. The heterometallic Tb-Pt bond lowers the symmetry of the Tb ion and enhanced the emission efficiency. In addition, the Tb-Pt complex shows field-induced multiple magnetic relaxation pathways. Furthermore, it served as an antenna for the observed dual emission. In other words, the heterometallic Tb-Pt bond has a significant effect on the luminescence and magnetic properties of the complex.

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Field-Induced Slow Magnetic Relaxation of Gd-III Complex with a Pt-Gd Heterometallic Bond

Takefumi Yoshida, Goulven Cosquer, David Chukwuma Izuogu, Hiroyoshi Ohtsu, Masaki Kawano, Yanhua Lan, Wolfgang Wernsdorfer, Hiroyuki Nojiri, Brian K. Breedlove, Masahiro Yamashita （Part： Lead author,　Corresponding author )

CHEMISTRY-A EUROPEAN JOURNAL ( WILEY-V C H VERLAG GMBH ) 23 ( 19 ) 4551 - 4556 2017.04 [Refereed]

Heterometallic Gd-Pt complexes ([Gd2Pt3(H2O)(2)(SAc)(12)] (SAc=thioacetate), [Y1.4Gd0.6Pt3(H2O)(2)(SAc)(12)], and [Gd2Pt3(H2O)(6)(SAc)(12)]7H(2)O have been synthesized. The crystal structures and DFT calculations indicated a Gd-Pt heretometallic bond. Single-crystal ESR spectra determined the direction of magnetic anisotropy as direction of the Gd-Pt bond. In other words, the Gd-Pt bond dictates the direction of magnetic anisotropy. The heterometallic Gd-Pt bond lowers the symmetry of the Gd ion, splitting the Kramers doublet in a dc field. Thus, we observed clear field-induced slow magnetic relaxation of [Y1.4Gd0.6Pt3(H2O)(2)(SAc)(12)] up to 36K. The relaxation process was determined to be a direct process.

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Temperature dependence of Peierls-Hubbard phase transition in [Pd(cptn)(2)Br]Br-2 studied by scanning tunneling microscopy

Yuka Hosomi, Shoji Yoshida, Atsushi Taninaka, Takefumi Yoshida, Shinya Takaishi, Osamu Takeuchi, Masahiro Yamashita, Hidemi Shigekawa

JAPANESE JOURNAL OF APPLIED PHYSICS ( IOP PUBLISHING LTD ) 55 ( 8 ) 08NB16 2016.08 [Refereed]

The temperature dependence of the Peierls-Hubbard phase transition in [Pd(cptn)(2)Br]Br-2 (cptn: 1R,2R diaminocyclopentane) was directly observed using a low-temperature scanning tunneling microscope. A short ligand without alkyl chains was used to form a rigid crystal lattice to reduce the effect of structural changes in the crystal with temperature. The hysteresis in the temperature dependence of the ratio between the areas of the charge density wave (CDW) state produced by the Pd-II-Pd-IV mixed-valence state and the Mott-Hubbard (MH) state with a Pd-III-averaged valence state which is a characteristic of the first-order phase transition, was directly observed at the atomic scale. Pinning of the CDW phase by defects was observed below the critical temperature, suggesting the growth of the CDW phase with defects as nuclei. (C) 2016 The Japan Society of Applied Physics

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Direct Observation of Ordered High-Spin-Low-Spin Intermediate States of an Iron(III) Three-Step Spin-Crossover Complex

Zhao-Yang Li, Hiroyoshi Ohtsu, Tatsuhiro Kojima, Jing-Wei Dai, Takefumi Yoshida, Brian K. Breedlove, Wei-Xiong Zhang, Hiroaki Iguchi, Osamu Sato, Masaki Kawano, Masahiro Yamashita

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION ( WILEY-V C H VERLAG GMBH ) 55 ( 17 ) 5184 - 5189 2016.04 [Refereed]

A neutral mononuclear Fe-III complex [Fe-III(H-5-Br-thsa-Me)(5-Br-thsa-Me)]H2O (1; H-2-5-Br-thsa-Me=5-bromosalicylaldehyde methylthiosemicarbazone) was prepared that exhibited a three-step spin-crossover (SCO) with symmetry breaking and a 14K hysteresis loop owing to strong cooperativity. Two ordered intermediate states of 1 were observed, 4HS-2LS and 2HS-4LS, which exhibited reentrant phase-transition behavior. This study provides a new platform for examining multistability in SCO complexes.

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Optically Visible Phase Separation between Mott-Hubbard and Charge-Density-Wave Domains in a Pd-Br Chain Complex

Takefumi Yoshida, Shinya Takaishi, Hiroaki Iguchi, Hiroshi Okamoto, Hisaaki Tanaka, Shin-ichi Kuroda, Yuka Hosomi, Shoji Yoshida, Hidemi Shigekawa, Tatsuhiro Kojima, Hiroyoshi Ohtsu, Masaki Kawano, Brian K. Breedlove, Laurent Guerin, Masahiro Yamashita （Part： Lead author )

CHEMISTRYSELECT ( WILEY-V C H VERLAG GMBH ) 1 ( 2 ) 259 - 263 2016.02 [Refereed]

We synthesized a bromo-bridged Pd complex, which underwent as lowering the temperature a charge-density-wave (CDW) to Mott-Hubbard (MH) phase transition, as confirmed by using X-ray diffraction analysis, ESR, FT-IR and Raman spectroscopies. The complex showed a phase-separation phenomenon with a striped pattern over a wide temperature range, and domain propagation was observed using an optical microscope. Moreover, we observed changes in the local electronic state accompanying the phase transition by using scanning tunneling microscopy (STM).

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17pAF-7 Electronic state of Br bridged Pd complex exhibiting CDW-MH transition

Takaishi,S, Yoshida,T, Yamashita,M, Okamoto,H, Tanaka,H, Kuroda,S, Hosomi,Y, Yoshida,S, Shigekawa,H

日本物理学会講演概要集 ( The Physical Society of Japan (JPS) ) 70 ( 2 ) 1577 - 1577 2015.09

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Peierls-Mott transition of one dimensional organic conductor observed by STM

Hosomi Yuka, Yoshida Shoji, Takaisi Shinya, Yamashita Masahiro, Yoshida Takehumi, Takeuti Osamu, Shigekawa Hidemi

Abstract of annual meeting of the Surface Science of Japan ( The Surface Science Society of Japan ) 35 329 - 329 2015

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Published Papers - YOSHIDA Takefumi