Updated on 2024/07/15

写真a

 
OKAZAWA, Atsushi
 
Affiliation
Faculty of Science and Engineering, School of Advanced Science and Engineering
Job title
Assistant Professor(non-tenure-track)
Degree
博士(理学) ( 電気通信大学 )
修士(工学) ( 電気通信大学 )
学士(工学) ( 電気通信大学 )

Research Experience

  • 2022.04
    -
    Now

    Waseda University   Department of Electrical Engineering and Bioscience, School of Advanced Science and Engineering   Assistant Professor

  • 2020.04
    -
    2022.03

    Nihon University   Division of Chemistry, Institute of Liberal Education, School of Medicine   Assistant Professor

  • 2009.08
    -
    2020.03

    Graduate School of Arts and Sciences, The University of Tokyo   Assistant Professor

  • 2009.04
    -
    2009.08

    日本学術振興会   特別研究員(PD)

  • 2008.04
    -
    2009.03

    Japan Society for the Promotion of Science   Research Fellowships for Young Scientists (DC2)

  • 2008.04
    -
    2009.03

    日本学術振興会   特別研究員(DC2)

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Education Background

  • 2006.04
    -
    2009.03

    The University of Electro-Communications   Graduate School of Electro-Communications   Department of Applied Physics and Chemistry (Doctor's course)  

  • 2004.04
    -
    2006.03

    The University of Electro-Communications   Graduate School of Electro-Communications   Department of Applied Physics and Chemistry (Master's course)  

  • 2000.04
    -
    2004.03

    The University of Electro-Communications   Faculty of Electro-Communications   Department of Applied Physics and Chemistry  

Professional Memberships

  • 2012.03
    -
    Now

    メスバウアー分光研究会

  • 2009.08
    -
    Now

    錯体化学会

  • 2009.08
    -
    Now

    アメリカ化学会

  • 2007.08
    -
    Now

    電子スピンサイエンス学会

  • 2006.09
    -
    Now

    分子科学会

  • 2004.12
    -
    Now

    日本化学会

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Research Areas

  • Inorganic/coordination chemistry / Functional solid state chemistry

Research Interests

  • Redox flow battery

  • Mossbauer spectroscopy

  • Organic radical

  • Organic-inorganic hybrid materials

  • 分子性磁性体

  • 単分子磁石

  • 有機・錯体物性化学

  • Single-molecule magnets

  • Molecule-based magnets

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Awards

  • The 3rd New Chemical Technology Research Encouragement Award

    2014.05  

    Winner: OKAZAWA, Atsushi

  • CSJ Presentation Award 2013

    2013.03   The Chemical Society of Japan  

    Winner: OKAZAWA, Atsushi

  • 26th Inoue Research Award for Young Scientists

    2009.12  

  • CSJ Student Presentation Award 2009

    2009.04   The Chemical Society of Japan  

  • ISESS-SEST2007 Oral Award

    2007.11   The Society of Electron Spin Science and Technology   Exchange Coupling and Energy-Level Structure of 4f3d Single-Molecule Magnets Determined by High-Frequency EPR

  • ICMM2006 Poster Prize

    2006.08   The 10th International Conference on Molecule-based Magnets (ICMM2006)   Preparation, Structures, and Magnetic Properties of Chelating Compounds of 2-Pyridyl Nitroxide Derivatives

     View Summary

    2nd prize Student Poster Competition

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Papers

  • Iron-based catholytes for aqueous redox-flow batteries

    Atsushi Okazawa, Takayuki Kakuchi, Kosuke Kawai, Masashi Okubo

    APL Materials   11 ( 11 ) 110901  2023.11  [Refereed]  [Invited]

     View Summary

    Redox-flow batteries (RFBs) are promising electrochemical energy storage devices to load-level intermittent power from renewable energy. In particular, aqueous RFBs using aqueous electrolytes possess several advantages over nonaqueous ones, such as low fabrication cost, nontoxicity, safety, and environmental benignity. Therefore, developing high-performance, abundant, less-expensive iron-based catholytes for aqueous RFBs is essential toward their wide deployment in a power grid. In this Perspective, we summarize the recent progress of iron-based catholytes for aqueous RFBs. We emphasize that iron-based catholytes possess widely ranged redox potentials (−1.0 to 1.5 V vs standard hydrogen electrodes) and solubility in water (0.2–4.0 mol L−1), thereby providing a wide range of cell performance. The molecular design, such as ligand functionalization, counter ion mixing, and asymmetrization, allows for rationally improving solubility, redox potential, and energy density. Furthermore, we demonstrate a simple evaluation method of the redox potential of iron-based catholytes using the calculated energy levels of the lowest unoccupied molecular orbital of ligand molecules. Finally, we rationalize the design strategy of iron-based catholytes for advanced aqueous RFBs.

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  • Development of an Iron(II) Complex Exhibiting Thermal- and Photoinduced Double Proton-Transfer-Coupled Spin Transition in a Short Hydrogen Bond

    Takumi Nakanishi, Yuta Hori, Yasuteru Shigeta, Hiroyasu Sato, Ryoji Kiyanagi, Koji Munakata, Takashi Ohhara, Atsushi Okazawa, Rintaro Shimada, Akira Sakamoto, Osamu Sato

    Journal of the American Chemical Society    2023.08

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  • Magnetoelectricity Enhanced by Electron Redistribution in a Spin Crossover [FeCo] Complex

    Xiaopeng Zhang, Wen-Huang Xu, Wenwei Zheng, Sheng-Qun Su, Yu-Bo Huang, Qirui Shui, Tianchi Ji, Mikoto Uematsu, Qian Chen, Masashi Tokunaga, Kaige Gao, Atsushi Okazawa, Shinji Kanegawa, Shu-Qi Wu, Osamu Sato

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   145 ( 29 ) 15647 - 15651  2023.07

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    Molecular-basedmagnetoelectric materials are among themost promisingmaterials for next-generation magnetoelectric memory devices. However,practical application of existing molecular systems has proven difficultlargely because the polarization change is far lower than the practicalthreshold of the ME memory devices. Herein, we successfully obtainedan [FeCo] dinuclear complex that exhibits a magnetic field-inducedspin crossover process, resulting in a significant polarization changeof 0.45 & mu;C cm(-2). Mo''ssbauer spectroscopyand theoretical calculations suggest that the asymmetric structuralchange, coupled with electron redistribution, leads to the observedpolarization change. Our approach provides a new strategy toward rationallyenhancing the polarization change.

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  • Investigation for Unique Magnetic Behaviours of Isomers in 1,2-Dithiooxalato-Bridged Diiron(II) Complex

    Takuya KANETOMO, Koki Yokoyama, Yudai Suzuki, Hiromichi Ida, Atsushi Okazawa, Masaya Enomoto

    Dalton Transactions    2023

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    1,2-Dithiooxalate (dto) can be employed as a bridging ligand and gives symmetric (O,S-chelation) or asymmetric (O,O- and S,S-chelation) coordination modes. In this study, we have prepared a novel dto-bridged diiron(II)...

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  • 57Fe Mössbauer Spectroscopy and High-Pressure Structural Analysis for Mechanism of Pressure-Induced Unique Magnetic Behaviour in (cation)[FeIIFeIII(dto)3] (cation = Ph4P and nPrPh3P; dto = 1,2-dithiooxalato)

    Ryosuke Taniai, Tsubasa Endo, Takuya KANETOMO, Atsushi Okazawa, Hirokazu Kadobayashi, Saori I. Kawaguchi, Masaya Enomoto

    Dalton Transactions   52 ( 24 ) 8368 - 8375  2023

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    A mixed-valence iron(II,III) coordination polymer, (Ph4P)[FeIIFeIII(dto)3] (2; Ph4P = tetraphenylphosphonium, dto = 1,2-dithiooxalato), exhibits a thermal hysteresis loop and low-temperature shift of the ferromagnetic phase transition temperature, with an increasing...

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  • Photoinduced Persistent Polarization Change in a Spin Transition Crystal

    Sheng‐Qun Su, Shu‐Qi Wu, Yu‐Bo Huang, Wen‐Huang Xu, Kai‐Ge Gao, Atsushi Okazawa, Hajime Okajima, Akira Sakamoto, Shinji Kanegawa, Osamu Sato

    Angewandte Chemie International Edition   61 ( 39 )  2022.09

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    Using light as a local heat source to induce a temporary pyroelectric current is widely recognized as an effective way to control the polarization of crystalline materials. In contrast, harnessing light directly to modulate the polarization of a crystal via excitation of the electronic bands remains less explored. In this study, we report an Fe-II spin crossover crystal that exhibits photoinduced macroscopic polarization change upon excitation by green light. When the excited crystal relaxes to the ground state, the corresponding pyroelectric current can be detected. An analysis of the structures, magnetic properties and the Mossbauer and infrared spectra of the complex, supported by calculations, revealed that the polarization change is dictated by the directional relative movement of ions during the spin transition process. The spin transition and polarization change occur simultaneously in response to light stimulus, which demonstrates the enormous potential of polar spin crossover systems in the field of optoelectronic materials.

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  • Manipulating electron redistribution to achieve electronic pyroelectricity in molecular [FeCo] crystals.

    Pritam Sadhukhan, Shu-Qi Wu, Jeremy Ian Long, Takumi Nakanishi, Shinji Kanegawa, Kaige Gao, Kaoru Yamamoto, Hajime Okajima, Akira Sakamoto, Michael L Baker, Thomas Kroll, Dimosthenis Sokaras, Atsushi Okazawa, Norimichi Kojima, Yoshihito Shiota, Kazunari Yoshizawa, Osamu Sato

    Nature communications   12 ( 1 ) 4836 - 4836  2021.08  [International journal]

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    Pyroelectricity plays a crucial role in modern sensors and energy conversion devices. However, obtaining materials with large and nearly constant pyroelectric coefficients over a wide temperature range for practical uses remains a formidable challenge. Attempting to discover a solution to this obstacle, we combined molecular design of labile electronic structure with the crystal engineering of the molecular orientation in lattice. This combination results in electronic pyroelectricity of purely molecular origin. Here, we report a polar crystal of an [FeCo] dinuclear complex exhibiting a peculiar pyroelectric behavior (a substantial sharp pyroelectric current peak and an unusual continuous pyroelectric current at higher temperatures) which is caused by a combination of Fe spin crossover (SCO) and electron transfer between the high-spin Fe ion and redox-active ligand, namely valence tautomerism (VT). As a result, temperature dependence of the pyroelectric behavior reported here is opposite from conventional ferroelectrics and originates from a transition between three distinct electronic structures. The obtained pyroelectric coefficient is comparable to that of polyvinylidene difluoride at room temperature.

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  • Transparent Ion-Exchange Membrane Exhibiting Intense Emission under a Specific pH Condition Based on Polypyridyl Ruthenium(II) Complex with Two Imidazophenanthroline Groups.

    Hajime Kamebuchi, Satoshi Tamaki, Atsushi Okazawa, Norimichi Kojima

    Membranes   11 ( 6 )  2021.05  [International journal]

     View Summary

    The development and the photophysical behavior of a transparent ion-exchange membrane based on a pH-sensitive polypyridyl ruthenium(II) complex, [(bpy)2RuII(H2bpib)RuII(bpy)2](ClO4)4 (bpy = 2,2'-bipyridine, H2bpib = 1,4-bis([1,10]phenanthroline[5,6-d]-imidazol-2-yl)benzene), are experimentally and theoretically reported. The emission spectra of [(bpy)2RuII(H2bpib)RuII(bpy)2]@Nafion film were observed between pH 2 and pH 11 and showed the highest relative emission intensity at pH 5 (λmaxem = 594.4 nm). The relative emission intensity of the film significantly decreased down to 75% at pH 2 and 11 compared to that of pH 5. The quantum yields (Φ) and lifetimes (τ) showed similar correlations with respect to pH, Φ = 0.13 and τ = 1237 ns at pH 5, and Φ = 0.087 and τ = 1014 ns and Φ = 0.069 and τ = 954 ns at pH 2 and pH 11, respectively. These photophysical data are overall considerably superior to those of the solution, with the radiative- (kr) and non-radiative rate constants (knr) at pH 5 estimated to be kr = 1.06 × 105 s-1 and knr = 7.03 × 105 s-1. Density functional theory calculations suggested the contribution of ligand-to-ligand- and intraligand charge transfer to the imidazolium moiety in Ru-H3bpib species, implying that the positive charge on the H3bpib ligand works as a quencher. The Ru-Hbpib species seems to enhance non-radiative deactivation by reducing the energy of the upper-lying metal-centered excited state. These would be responsible for the pH-dependent "off-on-off" emission behavior.

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  • Triplet Excited States Modulated by Push–Pull Substituents in Monocyclometalated Iridium(III) Photosensitizers

    Shin-ya Takizawa, Sora Katoh, Atsushi Okazawa, Naoya Ikuta, Satoko Matsushima, Fanyang Zeng, Shigeru Murata

    Inorganic Chemistry   60 ( 7 ) 4891 - 4903  2021.03

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  • Molecular Magnetism of Metal Complexes and Light-Induced Phase Transitions

    Norimichi Kojima, Atsushi Okazawa

    MODERN MOSSBAUER SPECTROSCOPY: NEW CHALLENGES BASED ON CUTTING-EDGE TECHNIQUES   137   267 - 317  2021

     View Summary

    One of the most attractive research in the field of molecular solids is multifunctional molecular magnets coupled with spin, charge and photon, and single-molecular magnet/single-chain magnet toward spintronics. In this chapter, we focus on the molecular magnetism and its related light-induced phase transitions from the viewpoint of Mossbauer spectroscopy. In the Sect. 6.1, the outline of this chapter is described. In the Sect. 6.2, static and dynamic spin crossover phenomena between the high-spin and low-spin states, and the spin frustration system induced by dynamic spin crossover phenomena for [MnIIFeIII(C2O3S)(3)] complex are described. In the Sect. 6.3, metal complexes showing charge transfer phase transitions such as Prussian blue analogous complexes and [FeIIFeIII(C2O2S2)(3)] complexes and their photoinduced phase transitions are described. In the Sect. 6.4, various kinds of molecular magnets including single molecular chain magnets are described.

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  • Three‐Step Spin State Transition and Hysteretic Proton Transfer in the Crystal of an Iron(II) Hydrazone Complex

    Takumi Nakanishi, Yuta Hori, Shuqi Wu, Hiroyasu Sato, Atsushi Okazawa, Norimichi Kojima, Yusuke Horie, Hajime Okajima, Akira Sakamoto, Yoshihito Shiota, Kazunari Yoshizawa, Osamu Sato

    Angewandte Chemie International Edition   59 ( 35 ) 14781 - 14787  2020.08  [Refereed]

     View Summary

    A proton-electron coupling system, exhibiting unique bistability or multistability of the protonated state, is an attractive target for developing new switchable materials based on proton dynamics. Herein, we present an iron(II) hydrazone crystalline compound, which displays the stepwise transition and bistability of proton transfer at the crystal level. These phenomena are realized through the coupling with spin transition. Although the multi-step transition with hysteresis has been observed in various systems, the corresponding behavior of proton transfer has not been reported in crystalline systems; thus, the described iron(II) complex is the first example. Furthermore, because proton transfer occurs only in one of the two ligands and yr electrons redistribute in it, the dipole moment of the iron(II) complexes changes with the proton transfer, wherein the total dipole moment in the crystal was canceled out owing to the antiferroelectric-like arrangement.

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  • Multicolor Emission and Photophysical Properties of Proton-Responsive Cyclometallated Iridium(III) Complex in Transparent Cation-Exchange Membrane

    Hajime Kamebuchi, Yu Fujimura, Taiho Yoshioka, Atsushi Okazawa, Makoto Tadokoro, Norimichi Kojima

    Crystals   10 ( 8 ) 653 - 653  2020.07

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  • In-beam Mossbauer spectra for Mn-57 implanted sulfur hexafluoride

    Yasuhiro Yamada, Yukiko Sato, Yoshio Kobayashi, Takatoshi Ando, Noriko Takahama, Kanako Some, Masami Sato, Mototugu Mihara, M. Kenya Kubo, Wataru Sato, Jun Miyazaki, Takashi Nagatomo, Junji Kobayashi, Atsushi Okazawa, Shinji Sato, Atsushi Kitagawa

    HYPERFINE INTERACTIONS   241 ( 1 )  2020.02

     View Summary

    To investigate the interactions of Fe-57 atoms with sulfur hexafluoride SF6 molecules, in-beam Mossbauer spectra were measured for Mn-57 implanted SF6 at 9 K and 65 K. Isolated Fe-57 atoms or ions produced by beta-decay were not trapped within the SF6 matrix. At 9 K, monomeric FeF2 and FeF3 molecules were produced by reaction of Fe-57 with F atoms released by decomposition of the SF6 molecules. When the temperature of the SF6 solid was increased to 65 K, FeF4 was formed in addition to FeF2 and FeF3. Density functional calculations were performed to confirm the assignments of the candidate species identified in the Mossbauer spectra.

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  • Modulating the ground state, stability and charge transport in OFETs of biradicaloid hexahydro-diindenopyrene derivatives and a proposed method to estimate the biradical character

    Tanguy Jousselin-Oba, Masashi Mamada, Atsushi Okazawa, Jérome Marrot, Takayuki Ishida, Chihaya Adachi, Abderrahim Yassar, Michel Frigoli

    Chemical Science   11 ( 44 ) 12194 - 12205  2020  [Refereed]  [International journal]

     View Summary

    <p>Biradicaloid HDIP derivatives show that the Δ<italic>E</italic>S–T gap does not follow the reverse trend of the biradical character but depends more on the delocalization of the radical centres at the outer rings.</p>

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  • A useful preparation of ultrasmall iron oxide particles by using arc plasma deposition

    Yumi Ida, Atsushi Okazawa, Kazutaka Sonobe, Hisanori Muramatsu, Tetsuya Kambe, Takane Imaoka, Wang-Jae Chun, Makoto Tanabe, Kimihisa Yamamoto

    RSC Advances   10 ( 68 ) 41523 - 41531  2020  [Refereed]

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    <p>Finely size-controlled ultrasmall iron oxide particles (IOPs) on graphene nanosheets were usefully prepared by using pulsed arc plasma deposition. The IOPs are composed of a high crystallinity single γ-Fe2O3 component without annealing.</p>

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  • Chameleonic layered metal–organic frameworks with variable charge-ordered states triggered by temperature and guest molecules

    Jian Chen, Yoshihiro Sekine, Atsushi Okazawa, Hiroyasu Sato, Wataru Kosaka, Hitoshi Miyasaka

    Chemical Science   11 ( 14 ) 3610 - 3618  2020  [Refereed]

     View Summary

    <p>A two-dimensional honeycomb layer composed of tetraoxolene-bridged iron subunits whose charge-ordered states are multiply variable <italic>via</italic> thermal treatments and solvation/desolvation is present.</p>

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  • Navigated Self-Assembly of a Pd2L4 Cage by Modulation of an Energy Landscape under Kinetic Control

    Tomoki Tateishi, Satoshi Takahashi, Atsushi Okazawa, Vicente Martí-Centelles, Jianzhu Wang, Tatsuo Kojima, Paul J. Lusby, Hirofumi Sato, Shuichi Hiraoka

    Journal of the American Chemical Society   141 ( 50 ) 19669 - 19676  2019.12

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  • Temperature dependence of spherical electron transfer in a nanosized [Fe14] complex.

    Wei Huang, Shuqi Wu, Xiangwei Gu, Yao Li, Atsushi Okazawa, Norimichi Kojima, Shinya Hayami, Michael L Baker, Peter Bencok, Mariko Noguchi, Yuji Miyazaki, Motohiro Nakano, Takumi Nakanishi, Shinji Kanegawa, Yuji Inagaki, Tatsuya Kawae, Gui-Lin Zhuang, Yoshihito Shiota, Kazunari Yoshizawa, Dayu Wu, Osamu Sato

    Nature communications   10 ( 1 ) 5510 - 5510  2019.12  [Refereed]  [International journal]

     View Summary

    The study of transition metal clusters exhibiting fast electron hopping or delocalization remains challenging, because intermetallic communications mediated through bridging ligands are normally weak. Herein, we report the synthesis of a nanosized complex, [Fe(Tp)(CN)3]8[Fe(H2O)(DMSO)]6 (abbreviated as [Fe14], Tp-, hydrotris(pyrazolyl)borate; DMSO, dimethyl sulfoxide), which has a fluctuating valence due to two mobile d-electrons in its atomic layer shell. The rate of electron transfer of [Fe14] complex demonstrates the Arrhenius-type temperature dependence in the nanosized spheric surface, wherein high-spin centers are ferromagnetically coupled, producing an S = 14 ground state. The electron-hopping rate at room temperature is faster than the time scale of Mössbauer measurements (<~10-8 s). Partial reduction of N-terminal high spin FeIII sites and electron mediation ability of CN ligands lead to the observation of both an extensive electron transfer and magnetic coupling properties in a precisely atomic layered shell structure of a nanosized [Fe14] complex.

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  • Bifurcation of self-assembly pathways to sheet or cage controlled by kinetic template effect

    Leonardo Hayato Foianesi-Takeshige, Satoshi Takahashi, Tomoki Tateishi, Ryosuke Sekine, Atsushi Okazawa, Wenchao Zhu, Tatsuo Kojima, Koji Harano, Eiichi Nakamura, Hirofumi Sato, Shuichi Hiraoka

    Communications Chemistry   2 ( 1 )  2019.12

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  • Magnetic property and 57Fe Mössbauer analysis of dilute Fe and Nb codoped SrTiO<inf>3-δ</inf>(STO) perovskites

    Kiyoshi Nomura, Shuhei Yamakawa, Miki Kasari, Yuya Koike, Akio Nakanishi, Shiro Kubuki, Atsushi Okazawa

    Hyperfine Interactions   241 ( 1 )  2019.12  [Refereed]

     View Summary

    © 2019, Springer Nature Switzerland AG. Dilute Fe and Nb codoped SrTiO3-δ (STO) perovskites were prepared by a complex formation and thermal decomposition method. The structure, magnetization properties and chemical states of Fe and Nb codoped STO perovskites were characterized by XRD, VSM and Mössbauer spectrometry. Mössbauer spectra of 57Fe and Nb codoped STO perovskites consist of paramagnetic doublet and magnetic relaxation components. The 1% Fe + 5% Nb codoped STO sample showed the smallest lattice constant and the largest ferromagnetism among 0.5–4% Fe + 5% Nb codoped STO perovskites. The most distortion of cubic STO lattice and the largest magnetic relaxation in Mössbauer spectrum were observed for the 0.5% Fe and 5% Nb codoped STO perovskite. It is considered that diluted magnetism in this system is related with the deformation of cubic structure due to defects.

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  • Water-vapor Sensitive Spin-state Switching in an Iron(III) Complex with Nucleobase Pendants Making Flexible Hydrogen-bonded Networks

    Kagesawa Koichi, Ichikawa Yuki, Iguchi Hiroaki, Breedlove Brian K, Li Zhaoyang, Yamashita Masahiro, Okazawa Atsushi, Kosaka Wataru, Miyasaka Hitoshi

    CHEMISTRY LETTERS   48 ( 10 ) 1221 - 1224  2019.10  [Refereed]

     View Summary

    Sensitive chemo-switchable magnetic materials operating at room temperature are one of the most potential candidates for future chemical devices. Here, we report a discrete iron(III) complex that exhibits high-spin/low-spin switching, sensitive even to rare water-vapor atmosphere above room temperature. The transformation of the hydrogen-bonded network triggered by water molecules is closely associated with the spin-state changing.

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  • Observation of Proton Transfer Coupled Spin Transition and Trapping of Photoinduced Metastable Proton Transfer State in an Fe(II) Complex.

    Takumi Nakanishi, Yuta Hori, Hiroyasu Sato, Shu-Qi Wu, Atsushi Okazawa, Norimichi Kojima, Takashi Yamamoto, Yasuaki Einaga, Shinya Hayami, Yusuke Horie, Hajime Okajima, Akira Sakamoto, Yoshihito Shiota, Kazunari Yoshizawa, Osamu Sato

    Journal of the American Chemical Society   141 ( 36 ) 14384 - 14393  2019.09  [Refereed]  [International journal]

     View Summary

    An important technique to realize novel electron- and/or proton-based functionalities is to use a proton-electron coupling mechanism. When either a proton or electron is excited, the other one is modulated, producing synergistic functions. However, although compounds with proton-coupled electron transfer have been synthesized, crystalline molecular compounds that exhibit proton-transfer-coupled spin-transition (PCST) behavior have not been reported. Here, we report the first example of a PCST Fe(II) complex, wherein the proton lies on the N of hydrazone and pyridine moieties in the ligand at high-spin and low-spin Fe(II), respectively. When the Fe(II) complex is irradiated with light, intramolecular proton transfer occurs from pyridine to hydrazone in conjunction with the photoinduced spin transition via the PCST mechanism. Because the light-induced excited high-spin state is trapped at low temperatures in the Fe(II) complex-a phenomenon known as the light-induced excited-spin-state trapping effect-the light-induced proton-transfer state, wherein the proton lies on the N of hydrazone, is also trapped as a metastable state. The proton transfer was accomplished within 50 ps at 190 K. The bistable nature of the proton position, where the position can be switched by light irradiation, is useful for modulating proton-based functionalities in molecular devices.

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  • Moving Organic Molecules in Crystalline Solids: Gradual Structural Transition and Spin Transition/Crossover

    Kashiro Atsushi, Kyoden Yukiya, Okazawa Atsushi, Ishida Takayuki

    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN   77 ( 7 ) 684 - 695  2019.07  [Refereed]  [Invited]

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  • Determination of iron species, including biomineralized jarosite, in the iron-hyperaccumulator moss Scopelophila ligulata by Mossbauer, X-ray diffraction, and elemental analyses

    H. Nakajima, A. Okazawa, S. Kubuki, Q. Shen, K. Itoh

    BioMetals   32 ( 1 ) 171 - 184  2019.02  [Refereed]

     View Summary

    Scopelophila ligulata is an Fe-hyperaccumulator moss growing in acidic environments, but the mechanism of Fe accumulation remains unknown. To understand the mechanism, we determined Fe species in S. ligulata samples. The moss samples were collected from four sites in Japan. The concentrations of Fe, P, S, Cl, and K in them were measured by induced coupled plasma mass spectrometry. Fe species in some of them were determined by Mössbauer spectroscopy and were confirmed by X-ray diffraction analysis. Fe species in S. ligulata samples were determined to be jarosite, ferritin, high-spin Fe(II) species, and akaganeite. To our knowledge, this is the first report on the biomineralization of jarosite in mosses. This result, combined with the fact that bacteria, a fungus, and a grass mineralize jarosite, suggests that its biomineralization is a common characteristic in a wide variety of living organisms. These findings indicate that the biomineralization of jarosite occurs not only in the region-specific species but in species adapted to a low-pH and metal-contaminated environment in different regions, provide a better understanding of the mechanism of Fe accumulation in the Fe-hyperaccumulator moss S. ligulata, and offer new insights into the biomineralization of jarosite.

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  • Preparation of Superparamagnetic Fe3O4 Nanoparticles from Iron Sand Mediated by Soft Template and Their Performance as Antibacterial Agent

    A. Taufiq, A. F. Muyasaroh, Sunaryono, H. Susanto, N. Hidayat, N. Mufti, E. Suarsini, A. Hidayat, A. Okazawa, T. Ishida, Darminto

    Journal of Magnetics   23 ( 3 ) 337 - 344  2018.09  [Refereed]

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  • Unique Hydration/Dehydration-Induced Vapochromic Behavior of a Charge-Transfer Salt Comprising Viologen and Hexacyanidoferrate(II)

    Rikako Tanaka, Atsushi Okazawa, Hisashi Konaka, Akito Sasaki, Norimichi Kojima, Nobuyuki Matsushita

    Inorganic Chemistry   57 ( 4 ) 2209 - 2217  2018.02  [Refereed]

     View Summary

    We successfully prepared and crystallographically characterized the first intermolecular charge-transfer (CT)-based vapochromic compound, (EV)(H3O)2[Fe(CN)6] (1-Wet, EV2+: 1,1′-diethyl-4,4′-bipyridine-1,1′-diium), an ethyl viologen-containing CT salt. 1-Wet, which is purple in color, is transformed into a brown powder (1-Dry) upon exposure to methanol vapor, drying over silica gel, or heating
    1-Dry returns to 1-Wet upon exposure to water vapor. These color changes are induced by hydration and dehydration, and gravimetric analyses suggest that 1-Dry is the dehydrated form of 1-Wet, namely, (EV)(H)2[Fe(CN)6]. Interestingly, desorption of water molecules from the oxonium ions in 1-Wet produces isolated protons (H+) that remain in 1-Dry as counter cations. Powder X-ray crystal structure analysis of 1-Dry reveals the presence of very short contacts between the nitrogen atoms of adjacent [Fe(CN)6]4- anions in the crystal. The isolated protons are trapped between the nitrogen atoms of cyanido ligands to form very short N···H···N hydrogen bonds. A detailed comparison of the crystal structures of 1-Wet and 1-Dry reveals that hydration and dehydration induce changes in crystal packing and intermolecular CT interactions, resulting in reversible color changes.

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  • Structural Insight into Order-Disorder Transition and Charge-Transfer Phase Transition in an Iron Mixed-Valence Complex (n-C3H7)4N[FeIIFeIII(dto)3] with a Two-Dimensional Honeycomb Network

    M. Itoi, A. Okazawa, J. Yamaura, S. Maki, T. Komatsu, I. Maurin, E. Codjovi, K. Boukheddaden, N. Kojima

    Inorganic Chemistry   57 ( 21 ) 13728 - 13738  2018  [Refereed]

     View Summary

    The structural properties of the iron mixed-valence complex (n-C3H7)4N[FeIIFeIII(dto)3] (dto = dithiooxalato, C2O2S2) have been investigated by single-crystal X-ray diffraction (SCXRD) at low temperatures. (n-C3H7)4N[FeIIFeIII(dto)3] has two-dimensional (2D) honeycomb layers consisting of alternating FeII and FeIII arrays bonded by bis-bidentate dithiooxalato ligands. Upon cooling, a superlattice structure with q = (1/3, 1/3, 0) was observed below 260 K, which corresponds to an order-disorder transition of the (n-C3H7)4N+ ions between the honeycomb layers. The charge-transfer phase transition (CTPT) occurs at TC→1/2 ∼ 120 K and TC↑1/2 ∼ 90 K upon heating and cooling, respectively, with an electron transfer between the FeII and FeIII ions, accompanied by a spin-state change, FeII (S = 2; HS)-O2C2S2-FeIII (S = 1/2; LS) ↔ FeIII (S = 5/2; HS)-O2C2S2-FeII (S = 0; LS). During the CTPT, the intersheet [FeIIFeIII(dto)3] distance decreased monotonously upon cooling, and an abrupt structural contraction was observed in the hexagonal 2D network. The volume contraction during the CTPT was quite small (∼0.7%), and differences in the structural distortions at the FeS6 and FeO6 sites were not found in the vicinity of the CTPT. We also calculated the orbital energies and the occupied spin states for the [Fe(O2C2S2)3] and [Fe(S2C2O2)3] octahedra in the vicinity of the CTPT by density functional theory (DFT). Because the local symmetry around the two coordinating iron ions is already lowered to trigonal symmetry, the CTPT did not cause any further deformation. This symmetry invariance resulted in an absence of orbital contributions to the total entropy change (ΔS) in the CTPT, which is in agreement with the previous heat capacity measurements. [Nakamoto, T; Miyazaki, Y; Itoi, M; Ono, Y; Kojima, N; Sorai, M. Heat Capacity of the Mixed-Valence Complex {[(n-C3H7)4N][FeIIFeIII(dto)3]}∞, Phase Transition because of Electron Transfer, and a Change in Spin-State of the Whole System. Angew. Chem., Int. Ed. 2001, 40, 4716-4719.]

    DOI PubMed

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  • Ionic crystal containing protons (H+) As counter cations: Preparation and crystal structure of a salt of 4,4¤-bipiperidine-1,1¤-diium and hexacyanidoferrate(II)

    Rikako Tanaka, Atsushi Okazawa, Norimichi Kojima, Nobuyuki Matsushita

    Chemistry Letters   47 ( 6 ) 697 - 699  2018  [Refereed]

     View Summary

    A molecular salt with a bulky cation and anion, (H2bipip)-(H)2[Fe(CN)6] (1) (H2bipip2+: 4,4¤-bipiperidine-1,1¤-diium), has been prepared. The salt comprises protons (H+) as counter cations. Single-crystal X-ray structure analysis revealed that the proton is trapped between two cyanido ligands of [Fe(CN)6]41 anions, forming a very short N£H+£N hydrogen bond.

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  • A triplet biradical with double bidentate sites based on tert-butyl pyridyl nitroxide as a candidate for strong ferromagnetic couplers

    A. Okazawa, Y. Terakado, T. Ishida, N. Kojima

    New Journal of Chemistry   42   17874 - 17878  2018  [Refereed]

     View Summary

    &lt;B&gt;[Back Cover]&lt;/B&gt;

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  • Magnetic properties of V-substitution effect in an iron mixed valence complex

    Norihiro Shida, Yoshiki Suzawa, Michikazu Inaba, Atsushi Okazawa, Norimichi Kojima, Masaya Enomoto

    POLYHEDRON   136   143 - 148  2017.11  [Refereed]

     View Summary

    The iron mixed-valence complex (n-C3H7)(4)N[(FeFeIII)-Fe-II(dto)(3)] (dto = C2O2S2) exhibits a novel type of phase transition according electron transfer between FeII and FeIII called charge transfer phase transition (CTPT). The existence of the CTPT highly depends on the 3d metal substitution with Zn, Mn, Cr, or Co for corresponding Fe site in (n-C3H7)(4)N[(FeFeIII)-Fe-II(dto)(3)]. Here, we prepared a series of magnetically diluted complexes (n-C3H7)(4)N[Fe(II)Fe(III)1-xV(III)x(dto)(3)] (x = 01), and carried out investigation of magnetic properties. Judging from the magnetic susceptibility measurement, there is no suppression of the CTPT unlike other 3d metal substituted cases. Moreover, 57Fe Mossbauer spectroscopy revealed that about 60% of FeII sites changed their spin states from high spin to low spin in case of substitution rate for x = 1.00. Since the difference of hardness and softness between metallic ions (Fe-II, Fe-III and V-III) and coordination sites of ligand (O or S in dto), this behavior is explained by the linkage isomerization of bridging ligand in formation process of the complex. (C) 2017 Elsevier Ltd. All rights reserved.

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  • Enhanced magnetism of perovskite oxides, Sr(Sn, Fe) O3-delta, by substitution of nonmagnetic Ca and Ti ions

    Kiyoshi Nomura, Shigeyo Suzuki, Tomoya Mizunuma, Yuya Koike, Atsushi Okazawa

    HYPERFINE INTERACTIONS   238   81-1 - 9  2017.10  [Refereed]

     View Summary

    Magnetic properties of perovskite oxides, SrSn1-xFexO3-delta (x &lt;= 0.15), substituted with nonmagnetic Ca and Ti ions were studied. XRD patterns showed the orthorhombic structure (close to tetragonal) of (Sr1-yCay)(Sn1-xFex) O-3-delta and Sr(Sn1-x-yFexTiy)O3-delta. The cell volumes decreased with the increase of Ca and Ti doping rates. Although Ti-substituted Sr(Sn, Fe)O3-delta showed small saturation magnetizations as compared with non-Ti substituted one, the magnetization increased a little with Ti doping rates up to 15%. On the other hand, all Ca-substituted Sr(Sn, Fe)O3-delta showed larger saturation magnetization than non-Ca substituted one. Two doublets of Fe3+ and a doublet of Fe4+ were observed in Mossbauer spectra of Ca-substituted Sr(Sn, Fe)O3-delta with weak ferromagnetism, and two sextets of high spin Fe3+ were additionally observed in Mossbauer spectra of Ca-doped Sr(Sn, Fe)O3-delta with relatively strong ferromagnetism. When Sr(Sn, Fe)O3-delta were further codoped with Ca and Ti ions, they showed the stable and enhanced ferromagnetic properties. It is considered that magnetic polarons among high spin Fe3+ species are overlapped by shrinking or deforming the crystal structure of perovskite oxides. That is the magnetism induced by a chemical pressure of perovskite oxides.

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  • Fe-57 and Sn-119 Mossbauer study of SrSnO3-delta doped with Fe and Sb under external magnetic fields

    Kiyoshi Nomura, Shigeyo Suzuki, Yuya Koike, Atsushi Okazawa, Yasuhiro Kobayashi, Masashi Kaneko

    HYPERFINE INTERACTIONS   238   70-1 - 8  2017.10  [Refereed]

     View Summary

    SrSn(1-x-y)Fe(x)Sb(y)O(3- delta)was prepared by a sol-gel and thermal annealing method. The lattice parameters of SrSn(0.97-x)FexSb(0.03)O(3-delta) (x = 0.04-0.15) decreased with the increase of Fe doping rates. All samples showed ferromagnetic behavior together with a paramagnetic component, relatively strong ferromagnetism for SrSn0.97-xFexSb0.03O3-delta and SrSn(1-x)FexO(3-delta) with Fe doping rates over 6% and 8%, respectively The Sb doping leads to the ferromagnetic behavior for the samples with the low-concentration of Fe dopant. Sn-119 Mossbauer spectra of SrSn0.92Fe0.08O3-delta and SrSn0.88Fe0.12O3-delta provided a broad doublet under a magnetic field of 0.85 T. The doublet could be analyzed as a magnetic sextet with 0.76 T. In Fe-57 Mossbauer spectra of SrSn0.88Fe0.12O3-delta under zero and 0.85 T different line intensity ratios of two sextets were observed. It suggests that the magnetic spin structure of SrSn(1-x)FexO(3-delta) is transversely ferrimagnetic.

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  • Studies on Nanostructure and Magnetic Behaviors of Mn-Doped Black Iron Oxide Magnetic Fluids Synthesized from Iron Sand

    Ahmad Taufiq, Sunaryono, Nurul Hidayat, Arif Hidayat, Edy Giri Rachman Putra, Atsushi Okazawa, Isao Watanabe, Norimichi Kojima, Suminar Pratapa, Darminto

    NANO   12 ( 9 ) 1750110-1 - 11  2017.09  [Refereed]

     View Summary

    Manganese (Mn)-doped black iron oxide (Fe3O4) magneticuids in the system of MnxFe(3-x)O(4) were successfully synthesized from natural magnetite (iron sand) by using co-precipitation method at room temperature. The analyses of the small angle neutron scattering (SANS) data by applying a log-normal sphere with a mass fractal models for x = 0 and x = 0: 25 and two lognormal spheres with a single mass fractal models for x 0: 5, 0.75 and 1 revealed that the primary particles of the MnxFe(3-x)O(4) fluids tended to decrease from 3.8 nm to 1.5nm along with the increasing fraction of Mn contents. The fractal dimension (D) increased from about 1.2 to 2.7 as the Mn contents were increasing; which physically represents an aggregation of the MnxFe(3-x)O(4) particles in the uids growing up from 1 to 3 dimensions to consolidate a more compact structure. The magnetization curves of the fluids exhibited an increasing saturation magnetization from x = 0 to x = 0: 25, and a decreasing on x = 0.5 and 0.75, with the maximum achievement of x = 1. These phenomena may probably be due to the combined e r ects, arising from cationic and dopant distributions, aggregation and its size, and also fractal dimension. Furthermore, the decrease of blocking temperature of the MnxFe(3-x)O(4) magneticuids could be associated with the reduced particle sizes, while the freezing temperature had its highest peak intensity when it collectively occurred with the blocking temperature at a similar point of about 270 K.

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  • Halogen substituent effect on the spin-transition temperature in spin-crossover Fe(III) compounds bearing salicylaldehyde 2-pyridyl hydrazone-type ligands and dicarboxylic acids

    Takumi Nakanishi, Atsushi Okazawa, Osamu Sato

    Inorganics   5 ( 3 ) 53-1 - 9  2017.09  [Refereed]

     View Summary

    Four Fe(III) spin-crossover (SCO) compounds, [Fe(HL1)2](HCl4TPA) (1-Cl), [Fe(HL1)2](HBr4TPA) (1-Br), [Fe(HL2)2](HCl4TPA) (2-Cl), and [Fe(HL2)2](HBr4TPA) (2-Br) (HL1 = 4-chloro-2-nitro-6-(1-(2-(pyridine-2-yl)hydrazono)ethyl)phenolate
    HL2 = 4-bromo-2-nitro-6-(1-(2- (pyridine-2-yl)hydrazono)ethyl)phenolate
    HCl4TPA = 2,3,5,6-tetrachloro-4-carboxybenzoate
    and HBr4TPA = 2,3,5,6-tetrabromo-4-carboxybenzoate), were synthesized to investigate the halogen substituent change effect in salicylaldehyde 2-pyridyl hydrazone-type ligands and dicarboxylic acids in SCO complexes to the spin-transition temperature. Crystal structure analyses showed that these compounds were isostructural. In addition, a one-dimensional hydrogen-bonded column was formed by the dicarboxylic acid anion and weak hydrogen bonds between the Fe(III) complexes. From Mössbauer spectroscopy and magnetic property measurements, these compounds were confirmed to exhibit gradual SCO. The spin-transition temperature can be shifted by changing the halogen substituent in the salicylaldehyde 2-pyridyl hydrazone-type ligands and dicarboxylic acids without changing the molecular arrangement in the crystal packing.

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  • Control of spin-crossover phenomena in one-dimensional triazole-coordinated iron(II) complexes by means of functional counter ions

    Akira Sugahara, Hajime Kamebuchi, Atsushi Okazawa, Masaya Enomoto, Norimichi Kojima

    Inorganics   5 ( 3 ) 50-1 - 23  2017.09  [Refereed]

     View Summary

    The spin-crossover (SCO) phenomenon between a high-spin and a low-spin state has attracted much attention in the field of materials science. Among the various kinds of SCO complexes, the triazole-bridged iron(II) polymeric chain system, [Fe(II)(R-trz)3]X2.xH2O (where trz is triazole and X is the anion), exhibiting the SCO phenomenon with thermal hysteresis around room temperature, has been extensively studied from the viewpoint of molecular memory and molecular devices. In connection with this system, we have controlled the SCO phenomenon according to the characteristic properties of counter ions. In the case of X being CnH2n+1SO3 -, the spin transition temperature (T1/2) increases with increasing the length (n) of the alkyl chain of the counter ion and saturates above n = 5, which is attributed to the increase in the intermolecular interaction of the alkyl chains of CnH2n+1SO3 -, called the fastener effect. The hysteresis width of T1/2 decreases with increasing n, showing the even-odd, also known as parity, effect. In the cases where X is toluenesulfonate (tos: CH3C6H4SO3 -) and aminobenzenesulfonate (abs: NH2C6H4SO3 -), T1/2 and its hysteresis width vary drastically with the structural isomerism (ortho-, metha-, and para-substitution) of counter ions, which implies the possibility of photoinduced spin transition by means of the photoisomerization of counter ions. From this strategy, we have synthesized [Fe(II)(NH2-trz)3](SP150)2·2H2O (SP150 = N-alkylsulfonated spiropyran) and investigated the SCO phenomenon. Moreover, we have developed [Fe(II)(R-trz)3]@Nafion films exhibiting spin transition around room temperature, where the Nafion membrane behaves as a counter anion as well as a transparent substrate, and investigated the photogenerated high-spin state below 35 K. The lifetime of the photogenerated high-spin state strongly depends on the intensity of irradiated light.

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  • Magneto-Structural Relationship on Strong Exchange Interactions between Chelating Nitroxide Radical and Transition-Metal Spins

    A. Okazawa

    IOP Conference Series: Materials Science and Engineering   202 ( 1 ) 012002-1 - 9  2017.05  [Refereed]

     View Summary

    To develop room-temperature molecule-based magnets, metal-radical approach is one of the most promising strategies. Strong magnetic interactions beyond a thermal energy of room temperature are essential for achieving such coveted materials. We have developed 2-pyridyl tert-butyl nitroxide (2pyNO) derivatives as a chelating radical ligand with a copper(II) or nickel(II) ion. The torsion angle (φ) around M-O-N-C2py is a useful metric in describing correlation between the structure and metal-radical exchange coupling 2J (defined as H = -2JΣSi •Si +1). Although we previously reported such a magneto-structural correlation, in this paper we updated the plot of 2J versus φ by dividing into two categories: the hexacoordinatenickel(II) and copper(II) complexes. An empirical linear correlation was formulated for both Cu and Ni categories, as 2J/k B = a + b|φ| with a = 503(112) K and b = -36(3) K deg-1 and with a = 449(46) K and b = -21.0(17) K deg-1, respectively. In the latter plot we confirm that the relationship can be generalized for the oxoverdazyl and dithiadiazolyl systems as well as the 2pyNO systems. The results are supported by the calculations based on the density functional theory.

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  • Synthesis and Magnetic Properties of Linear Two-coordinate Monomeric Diaryliron(II) Complexes Bearing Fused-ring Bulky "Rind" Groups

    Shun Goda, Masanori Nikai, Mikinao Ito, Daisuke Hashizume, Kohei Tamao, Atsushi Okazawa, Norimichi Kojima, Hiroyuki Fueno, Kazuyoshi Tanaka, Yoshio Kobayashi, Tsukasa Matsuo

    CHEMISTRY LETTERS   45 ( 6 ) 634 - 636  2016.06  [Refereed]

     View Summary

    Monomeric diaryliron(Il) complexes, Fe(Rind)(2), have been obtained by introducing fused-ring bulky "Rind" groups. For Fe(Eind)(2), a significant orbital contribution of the Fe(II) ion due to the linear two-coordination has been determined by the highly effective magnetic moment (mu(eff) = 5.82 mu(B)) and the extraordinarily large internal hyperfine field (H-n = ca. 140 T) in the Mossbauer spectrum. Variable-frequency out-of-phase ac susceptibility data demonstrate an effective spin-reversal barrier of U-eff = 51.2(7) cm(-1) associated with the single-ion magnet behavior.

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  • Small-Angle X-Ray Scattering Study on PVA/Fe3O4 Magnetic Hydrogels

    Sunaryono, Ahmad Taufiq, Edy Giri Rahman Putra, Atsushi Okazawa, Isao Watanabe, Norimichi Kojima, Supagorn Rugmai, Siriwat Soontaranon, Mohammad Zainuri, Triwikantoro, Suminar Pratapa, Darminto

    NANO   11 ( 3 ) 1650027-1 - 12  2016.03  [Refereed]

     View Summary

    A synchrotron small-angle X-ray scattering (SAXS) study on PVA/Fe3O4 magnetic hydrogels has been performed to investigate the effect of clustering on their magnetic properties. The hydrogels were prepared through freezing-thawing (F-T) processes. The structure, morphology and magnetic properties of magnetite (Fe3O4) nanoparticles (NPs) were investigated using X-ray diffractometry (XRD), transmission electron microscopy (TEM) and a superconducting quantum interference device (SQUID) magnetometer, respectively. In this study, SAXS data were used to reveal the structural dimensions of the magnetite and its distribution in the polymer-rich PVA and magnetic hydrogels. As calculated using the Beaucage and Teubner-Strey models, the average of the structural dimensions of the PVA hydrogels was 3.9 nm (crystallites), while the average distance between crystallites was approximately 18 nm. Further analysis by applying a two-lognormal distribution showed that the magnetite NPs comprised secondary particles with a diameter of 9.6 nm that were structured by primary particles (similar to 3.2 nm). A two-lognormal distribution function has also been used in describing the size distributions of magnetite NPs in magnetic hydrogels. The clusters of magnetite NPs in the magnetic hydrogels are significantly reduced from 30.4 nm to 12.8 nm with decreasing concentration of the NPs magnetite from 15 wt.% to 1 wt.%. The saturation magnetization values of the magnetite NPs, the 15% and 1% magnetic hydrogels were 34.67 emu/g, 6.52 emu/g and 0.37 emu/g, respectively.

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  • Magnetic property and Mossbauer analysis of SrSn1-xFexO3 prepared by a sol-gel method

    Kiyoshi Nomura, Shigeyo Suzuki, Yuya Koike, Hongling Li, Atsushi Okazawa, Norimichi Kojima

    HYPERFINE INTERACTIONS   237 ( 1 ) 26-1 - 10  2016.02  [Refereed]

     View Summary

    The dilute magnetic properties of SrSn1-xFexO3 (x = 0.01-0.15) prepared by sol-gel and thermal decomposition methods were investigated by Fe-57 Mossbauer spectrometry, magnetometry, and X-ray diffractometry. It was found that SrSnO3 doped with 2-8 % Fe show weak ferromagnetism although only paramagnetic doublets are observed in Fe-57 Mossbauer spectra at room temperature (RT), whereas SrSnO3 doped with 10-15 % Fe show relatively strong ferromagnetism, and the sextets are additionally observed in the Fe-57 Mossbauer spectra at RT. The weak ferromagnetism by doping 2-8 % Fe is considered to be caused by the induced magnetic defects, and the ferromagnetism by doping 10-15 % Fe are considered mainly due to the magnetic coupling between dilute Fe3+ partially substituted at Sn4+ sites in the orthorhombic structure of SrSnO3-delta accompanying the oxygen deficiencies. It is further remarkable that poor crystalline 8 % Fe doped SrSnO3-delta obtained by annealing at 600 degrees C shows relatively high saturation magnetization and low coercivity.

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  • Mossbauer and XRD analysis of corrosion products on weathering steel treated by wet-dry cycles using various solutions

    Matashige Oyabu, Kiyoshi Nomura, Yuya Koike, Atsushi Okazawa

    HYPERFINE INTERACTIONS   237 ( 1 ) 68-1 - 7  2016.02  [Refereed]

     View Summary

    Weathering steels (COR-TEN) were corroded by wet-dry cycles using a splay of various solutions in a laboratory. Corrosion products on weathering steel were characterized by X-ray diffractometry and Mossbauer spectrometry at room and low temperatures. Fine alpha-FeOOH, gamma-FeOOH and gamma-Fe2O3 are fundamentally formed in various atmospheric conditions. beta-FeOOH is additionally formed under the existence of chloride ions, but not formed when sulfate ions are coexisting. Spraying a NaF solution prevents the progress of corrosion.

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  • 1706 - Proton-responsive emission properties in cyclometalated iridium(III) complex film, [IrIII(bdp)3]@Nafion (bdp = 2,4’-(benzene-1,3-diyl)dipyridine)

    Hajime Kamebuchi, Yu Fujimura, Atsushi Okazawa, Makoto Tadokoro, Norimichi Kojima

    The 2015 International Chemical Congress of Pacific Basin Societies (PACIFICHEM 2015)    2015.12  [Refereed]

  • Nanoscale Clustering and Magnetic Properties of Mn (x) Fe3-x O-4 Particles Prepared from Natural Magnetite

    Ahmad Taufiq, Sunaryono, Edy Giri Rachman Putra, Atsushi Okazawa, Isao Watanabe, Norimichi Kojima, Suminar Pratapa, Darminto

    JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM   28 ( 9 ) 2855 - 2863  2015.09  [Refereed]

     View Summary

    A series of Mn (x) Fe3-x O-4 (0 a parts per thousand currency sign x a parts per thousand currency sign 1) nanoparticles was successfully synthesized via a simple coprecipitation method. The starting material was a natural magnetite purified from local iron sand. Crystallite nanoparticles were produced by drying without using a high calcination temperature. Rietveld analysis of the X-ray diffractometry (XRD) data for all samples demonstrated that the Mn ions partially substituted the Fe ions in the spinel cubic structure of the Fe3O4 to form Mn (x) Fe3-x O-4 phases. We applied two lognormal spherical and single mass fractal models to the analysis of the small-angle neutron scattering (SANS) data and revealed that the primary Mn (x) Fe3-x O-4 particles ranged in size from 1.5 to 3.8 nm and formed three-dimensional clusters as secondary structures. The samples displayed superparamagnetic behavior, having the saturation magnetization which was most likely influenced by the competing contribution from Mn, the sizes of the primary particles, and their clusters. Further analysis revealed that the zero-field-cooled and field-cooled curves of the Mn (x) Fe3-x O-4 nanoclusters exhibited a superparamagnetic phenomenon with the lowest magnetic blocking temperature approximately 145 K.

    DOI J-GLOBAL

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  • Development of a Photoresponsive Organic-Inorganic Hybrid Magnet: Layered Cobalt Hydroxides Intercalated with Spiropyran Anions

    Naru Tanaka, Atsushi Okazawa, Akira Sugahara, Norimichi Kojima

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   88 ( 8 ) 1150 - 1155  2015.08  [Refereed]

     View Summary

    To develop an organic inorganic hybrid photomagnet, we performed the intercalation of sulfonate-substituted spiropyran anions into layered cobalt hydroxides, obtaining the photoresponsive compound, Co(OH)(1.84)(nSPSO(3))(0.16)center dot 0.8H(2)O (CoLHSP; nSPSO(3): 1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indoline]-5'-sulfonate). After UV irradiation (313 nm), the optical and magnetic properties of CoLHSP clearly changed. A new band emerged in the absorption spectrum at 564 nm, corresponding to the pi-pi* transition in the open form of nSPSO(3). Moreover, the photoisomerization of nSPSO(3) induced a new ferrimagnetic phase transition at 10K in the temperature dependence of DC and AC magnetic susceptibilities in addition to the ferrimagnetic phase transition at 15K for the unirradiated sample. Analyzing the magnetic measurements before and after UV irradiation, we estimated the phototransformation ratio of the magnetic phase in CoLHSP at approximately 40%.

    DOI J-GLOBAL

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  • Study on spin configuration in photoresponsive iron mixed-valence complexes by Mossbauer spectroscopy

    A. Okazawa, J. Yoshida, N. Kida, I. Kashima, W. Murata, M. Enomoto, N. Kojima

    HYPERFINE INTERACTIONS   226 ( 1-3 ) 351 - 357  2014.04  [Refereed]

     View Summary

    We have investigated magnetic properties in a series of photoresponsive dithiooxalato (dto)-bridged iron mixed-valence complexes, (SP-R)[(FeFeIII)-Fe-II(dto)(3)] (SP-R = R-substituted pyridospiropyran cation; R = Me, Et, and Pr; abbreviated as 1 (Me), 1 (Et), and 1 (Pr), respectively). As for our previous reports, 1 (Me) and 1 (Et) show two-step succeeding ferromagnetic transitions at T (C) = 25 & 8 K and 22 & 5 K, respectively. However, 1 (Et) has no hysteresis in the magnetic susceptibility, while 1 (Me) undergoes the charge transfer phase transition with thermal hysteresis around 75 K. To elucidate the two-step transitions of them, we measured Fe-57 Mossbauer spectra of 1 (Et). The spectra of Fe-II (S = 2) and Fe-III (S = 1/2) in the HTP were observed in the magnetically ordered state as well as the paramagnetic state, and revealed that only HTP exists in a temperature range up to 5 K. The result is consistent with that of 1 (Pr), where one ferromagnetic phase transition occurs at T (C) = 10 K. Fe-57 Mossbauer spectroscopy is useful to clarify the origin of the succeeding magnetic transition for these systems.

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  • Sol-gel synthesis and dilute magnetism of nano MgO powder doped with Fe

    Kiyoshi Nomura, Souichirou Taya, Atsushi Okazawa, Norimichi Kojima

    HYPERFINE INTERACTIONS   226 ( 1-3 ) 161 - 169  2014.04  [Refereed]

     View Summary

    Mg oxides doped with 1 % Fe-57 were prepared by a sol-gel method, and annealed at various temperatures. Nano-size Mg oxides were characterized by Mossbauer spectrometry, magnetization and XRD measurements. The crystalline size of MgO increases with increase of annealing temperature. Samples annealed at 600 A degrees C and 800 A degrees C gave only doublet peaks of paramagnetic Fe3+ in Mossbauer spectra although Fe3+ doping into MgO induced a distorted structure and showed weak ferromagnetism. It is considered that the magnetic property is due to defect induced magnetism by doping Fe3+ into MgO. For a sample heated at 1000 A degrees C, it is found from low temperature Mossbauer spectra that Fe3+ species are located at the core and shell of fine MgFe2O4 grains and diluted in MgO matrix.

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  • Photochromic Property of Anionic Spiropyran with Sulfonate-substituted Indoline Moiety

    Akira Sugahara, Nara Tanaka, Atsushi Okazawa, Nobuyuld Matsushita, Norimichi Kojima

    CHEMISTRY LETTERS   43 ( 3 ) 281 - 283  2014.03  [Refereed]

     View Summary

    For fabricating photoresponsive multifunctional materials, we have developed the potassium salt of a new anionic spiropyran, 1',3',3'-trimethyl-6-nitrospiro [2H-1-benzopyran-2,2'-indoline]-5'-sulfonate (1(-)), with the sulfonate group present on the indoline moiety and whose crystal structure was revealed by single-crystal X-ray diffraction analysis. The photochromism of 1.K was demonstrated at room temperature in the KBr-diluted state, as well as in solution. The protonated spiropyran 1H shows negative photochromism.

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  • Abrupt Spin Transition with Thermal Hysteresis of Iron(III) Complex [Fe-III(Him)(2)(hapen)]AsF6 (Him = Imidazole, H(2)hapen = N,N '-Bis(2-hydroxyacetophenylidene)ethylenediamine)

    Takeshi Fujinami, Masataka Koike, Naohide Matsumoto, Yukinari Sunatsuki, Atsushi Okazawa, Norimichi Kojima

    INORGANIC CHEMISTRY   53 ( 4 ) 2254 - 2259  2014.02  [Refereed]

     View Summary

    The solvent-free spin crossover iron(III) complex [Fe-III(Him)(2)(hapen)]AsF6 (Him = imidazole, H(2)hapen = bis(2-hydroxyacetophenylidene)ethylenediamine), exhibiting thermal hysteresis, was synthesized and characterized. The Fern ion has an octahedral coordination geometry, with N2O2 donor atoms of the planar tetradentate ligand (hapen) and two nitrogen atoms of two imidazoles at the axial positions. One of two imidazoles is hydrogen-bonded to the phenoxo oxygen atom of hapen of the adjacent unit to give a hydrogen-bonded one-dimensional chain, while the other imidazole group is free from hydrogen bonding. The temperature dependencies of the magnetic susceptibilities and Mossbauer spectra revealed an abrupt spin transition between the high-spin (S = 5/2) and low-spin (S = 1/2) states, with thermal hysteresis.

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  • Study on static and dynamic spin-crossover tripyrazolylmethane iron(II) complexes by using μSR spectroscopy

    N. Kojima, H. Kobayashi, A. Okazawa, I. Kawasaki, I. Watanabe

    RIKEN Accelerator Progress Report   47   258  2014  [Refereed]

  • A tricky water molecule coordinated to a verdazyl radical-iron(II) complex: a multitechnique approach

    Hajime Kamebuchi, Masashi Okubo, Atsushi Okazawa, Masaya Enomoto, Jun Harada, Keiichiro Ogawa, Goro Maruta, Sadamu Takeda, Norimichi Kojima, Cyrille Train, Michel Verdaguer

    PHYSICAL CHEMISTRY CHEMICAL PHYSICS   16 ( 19 ) 9086 - 9095  2014  [Refereed]

     View Summary

    The first iron complexes of high-spin iron(II) species directly coordinated to verdazyl radicals, [Fe-11(vdCOO)(2)(H2O)(2)].2H(2)O (1; vdCOO(-) = 1,5-dimethyl-6-oxo-verdazyl-3-carboxylate) and [Fe-11(vdCOO)(2)(D2O)(2)].2D(2)O (2), were synthesized. The crystal structure of 1 was investigated by single-crystal X-ray diffraction at room temperature and at 90 K. The compound crystallizes in the P1 space group with no phase transition between 300 and 90 K. The crystals are composed of discrete [Fe-11(vdCOO)(2)(H2O)(2)] complexes and crystallization water molecules. In the complex, two vdCOO(-) ligands coordinate to the iron(II) ion in a head-to-tail arrangement and two water molecules complete the coordination sphere. The Fe-X (X = O, N) distances vary in the 2.069-2.213 A range at 300 K and in the 2.0679-2.2111 A range at 90 K, indicating that the iron(II) ion is in its high-spin (HS) state at both temperatures. At 300 K, one of the coordinated water molecules is H-bonded to two crystallization water molecules whereas the second one appears as loosely H-bonded to the two oxygen atoms of the carboxylate group of two neighboring complexes. At 90 K, the former H-bonds remain essentially the same whereas the second coordinated water molecule reveals a complicated behavior appearing simultaneously as tightly H- bonded to two oxygen atoms and non-H-bonded. The Fe-57 Mossbauer spectra, recorded between 300 K and 10 K, give a clue to this situation. They show two sets of doublets typical of HS iron(II) species whose intensity ratio varies smoothly with temperature. It demonstrates the existence of an equilibrium between the high temperature and low temperature forms of the compounds. The solid-state magic angle spinning H-2 NMR spectra of 2 were recorded between 310 K and 193 K. The spectra suggest the existence of a strongly temperature- dependent motion of one of the coordinated water molecules in the whole temperature range. Variable- temperature magnetic susceptibility measurements indicate an antiferromagnetic interaction (J(Fe-vd) = -27.1 cm(-1); H = -J(ij)S(i)S(j)) of the HS iron(II) ion and the radical spins with high g(Fe) and D-Fe values (g(Fe) = 2.25, D-Fe = +3.37 cm(-1)) for the HS iron(II) ion. Moreover, the radicals are strongly antiferromagnetically coupled through the iron(II) center (J(vd-vd) = -42.8 cm(-1)). These last results are analysed based on the framework of the magnetic orbitals formalism.

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  • Cation size effect on photomagnetism and charge transfer phase transition of iron mixed-valence complexes with spiropyrans

    Junya Yoshida, Noriyuki Kida, Atsushi Okazawa, Norimichi Kojima

    POLYHEDRON   66   102 - 107  2013.12  [Refereed]

     View Summary

    We have investigated the magnetic properties of a photoresponsive organic inorganic hybrid system, (SP-R)[(FeFeIII)-Fe-II(dto)(3)](SP = spiropyran; R = Me, Et, Pr; dto = C2O2S2), under hydrostatic pressures. At ambient pressure, (SP-Et)[(FeFeIII)-Fe-II(dto)(3)] and (SP-Pr)[(FeFeIII)-Fe-II(dto)(3)] undergo one and two ferromagnetic phase transitions corresponding to the high-temperature phase with the spin configuration of Fe-II(S = 2)-Fe-III(S = 1/2), while (SP-Me)[(FeFeIII)-Fe-II(dto)(3)] undergoes two ferromagnetic phase transitions corresponding to the coexistence of the high-temperature phase and the low-temperature phase with the spin configuration of Fe-II(S = 0)-Fe-III(S = 5/2). Under hydrostatic pressures, (SP-R)[(FeFeIII)-Fe-II(dto)(3)] (R = Et, Pr) undergo a new ferromagnetic phase transition corresponding to the low-temperature phase caused by the pressure-induced charge transfer phase transition. (C) 2013 Elsevier Ltd. All rights reserved.

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  • Exchange Coupling and Its Chemical Trend Studied by High-Frequency EPR on Heterometallic [Ln(2)Ni] Complexes

    Atsushi Okazawa, Takashi Shimada, Norimichi Kojima, Shunsuke Yoshi, Hiroyuki Nojiri, Takayuki Ishida

    INORGANIC CHEMISTRY   52 ( 23 ) 13351 - 13355  2013.12  [Refereed]

     View Summary

    We applied high-frequency electron paramagnetic resonance to trinuclear 4f-3d heterometallic complexes, [{Ln(hfac)(3)}(2){Ni(dpk)(2)(py)(2)}] (Ln = Y, Gd, Tb, and Ho; hfac = hexafluoroacetylacetonate, dpk = di-2-pyridyl ketoximate, and py = pyridine), and determined the exchange parameter J(Ln-Ni) as well as nickel(II) zero-field splitting parameters. In contrast to the antiferromagnetic Dy analogue, ferromagnetic couplings were precisely characterized as J(Gd-Ni)/k(B) = +0.301(4) K, J(Tb-Ni)/k(B) = +0.216(12) K, and J(Ho-Ni)/k(B) = +0.110(3) K (defined as -J(Ln-Ni)Sigma J(Ln)(z)S(Ni)).

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    13
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  • Alternating Ferro-and Antiferromagnetic Couplings in One-Dimensional Chain Hexachlorodicuprate(II), (MV)[CuCl3]2 (MV= Methyl Viologen)

    Y. Seki, A. Okazawa, M. Enomoto, J. Harada, K. Ogawa, N. Kojima

    Current Inorganic Chemistry   3 ( 2 ) 94 - 100  2013.06  [Refereed]

    DOI

  • Ground triplet pyrimidine-4,6-diyl bis(tert-butyl nitroxide) as a paramagnetic building block for metal-organic frameworks

    Yuta Homma, Atsushi Okazawa, Takayuki Ishida

    TETRAHEDRON LETTERS   54 ( 24 ) 3120 - 3123  2013.06  [Refereed]

     View Summary

    We synthesized pyrimidine-4,6-diyl bis(tert-butyl nitroxide) (pmbNO), and characterized as a biradical by means of ESR spectroscopy. The zero-field splitting parameters were vertical bar D vertical bar/hc = 2.52 x 10(-2) cm(-1) and vertical bar E vertical bar/hc = 2.34 x 10(-3) cm(-1) in frozen toluene at 100 K. Magnetic study clarified the presence of intramolecular ferromagnetic coupling with 2J/k(B) = +18.5(5) K in frozen toluene-ethanol. DFT calculation supports the ground triplet state of pmbNO. The reaction of pmbNO with Cu(hfac)(2) gave [Cu-3(pmbNO)(2)(hfac)(4)], and the structure was determined by X-ray crystallographic analysis. Though the ligand was reduced to be an anion radical, pmbNO is confirmed to work as a rigid bridge, and the nitroxide oxygen atoms can ligate the metal ions. (C) 2013 Elsevier Ltd. All rights reserved.

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  • Reversible Solid State Redox of an Octacyanometallate-Bridged Coordination Polymer by Electrochemical Ion Insertion/Extraction

    Masashi Okubo, Koichi Kagesawa, Yoshifumi Mizuno, Daisuke Asakura, Eiji Hosono, Tetsuichi Kudo, Haoshen Zhou, Kotaro Fujii, Hidehiro Uekusa, Shin-ichi Nishimura, Atsuo Yamada, Atsushi Okazawa, Norimichi Kojima

    INORGANIC CHEMISTRY   52 ( 7 ) 3772 - 3779  2013.04  [Refereed]

     View Summary

    Coordination polymers have significant potential for new functionality paradigms due to the intrinsic tunability of both their electronic and structural properties. In particular, octacyanometallate-bridged coordination polymers have the extended structural and magnetic diversity to achieve novel functionalities. We demonstrate that [Mn(H2O)][Mn(HCOO)(2/3)(H2O)(2/3)](3/4)[Mo(CN)(8)]center dot H2O can exhibit electrochemical alkali-ion insertion/extraction with high durability. The high durability is explained by the small lattice change of less than 1% during the reaction, as evidenced by ex situ X-ray diffraction analysis. The ex situ X-ray absorption spectroscopy revealed reversible redox of the octacyanometallate. Furthermore, the solid state redox of the paramagnetic [Mo-V(CN)(8)](3-)/diamagnetic[Mo-IV(CN)(8)](4-) couple realizes magnetic switching.

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  • Long-range and short-range orderings in K4Fe4P5O20 with a natrolite-like framework

    Zhangzhen He, Weilong Zhang, Wendan Cheng, Atsushi Okazawa, Norimichi Kojima

    DALTON TRANSACTIONS   42 ( 16 ) 5860 - 5865  2013  [Refereed]

     View Summary

    K4Fe4P5O20 shows an interesting natrolite-like structure with a spin-tetrahedron lattice built by mixed valence Fe ions. Single crystals of the title compound are successfully grown by the flux method using KF as flux. Magnetic results combined from magnetic, heat capacity, and Fe-57 Mossbauer spectra measurements show that K4Fe4P5O20 possesses a short-range magnetic ordering at similar to 13 K and a long-range ordering at similar to 7 K. Magnetic anisotropy of K4Fe4P5O20 is observed between H parallel to c and H perpendicular to c, suggesting that the c-axis is the magnetic easy-axis. The spin arrangements in the system are suggested to be ferrimagnetic along the natrolite chains.

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  • Electrochemical Mg2+ intercalation into a bimetallic CuFe Prussian blue analog in aqueous electrolytes

    Yoshifumi Mizuno, Masashi Okubo, Eiji Hosono, Tetsuichi Kudo, Katsuyoshi Oh-ishi, Atsushi Okazawa, Norimichi Kojima, Ryosuke Kurono, Shin-ichi Nishimura, Atsuo Yamada

    JOURNAL OF MATERIALS CHEMISTRY A   1 ( 42 ) 13055 - 13059  2013  [Refereed]

     View Summary

    Mg2+ intercalation/deintercalation is achieved by using aqueous electrolytes and Prussian blue analog electrodes. Ex situ X-ray diffraction evidenced the solid solution process of Mg2+ intercalation/deintercalation, while the Fe-57 Mossbauer spectroscopy and X-ray absorption near edge structure revealed redox of both Cu and Fe.

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  • Anionic Iron Complexes with a Bond between an Ate-Type Pentacoordinated Germanium and an Iron Atom

    Naokazu Kano, Naohito Yoshinari, Yusuke Shibata, Mariko Miyachi, Takayuki Kawashima, Masaya Enomoto, Atsushi Okazawa, Norimichi Kojima, Jing-Dong Guo, Shigeru Nagase

    ORGANOMETALLICS   31 ( 23 ) 8059 - 8062  2012.12  [Refereed]

     View Summary

    The first stable anionic iron(0) complexes bearing an ate-type pentacoordinated germanium(IV) ligand were synthesized. The X-ray crystallographic analysis shows trigonal-bipyramidal and piano-stool geometries of germanium and iron, respectively. The complexes have moderately electron-rich iron centers and polar Ge-Fe bonds which can be cleaved by oxidation.

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  • Precise Electrochemical Control of Ferromagnetism in a Cyanide-Bridged Bimetallic Coordination Polymer

    Yoshifumi Mizuno, Masashi Okubo, Koichi Kagesawa, Daisuke Asakura, Tetsuichi Kudo, Haoshen Zhou, Katsuyoshi Oh-ishi, Atsushi Okazawa, Norimichi Kojima

    INORGANIC CHEMISTRY   51 ( 19 ) 10311 - 10316  2012.10  [Refereed]

     View Summary

    Magnetic coordination polymers can exhibit controllable magnetism by introducing responsiveness to external stimuli. This report describes the precise control of magnetism of a cyanide-bridged bimetallic coordination polymer (Prussian blue analogue: PBA) through use of an electrochemical quantitative Li ion titration technique, i.e., the galvanostatic intermittent titration technique (GITT). K0.2Ni[Fe(CN)(6)](0.7)center dot 4.7H(2)O (NiFe-PBA) shows Li ion insertion/extraction reversibly accompanied with reversible Fe3+/Fe2+ reduction/oxidation. When Li ion is inserted quantitatively into NiFe-PBA, the ferromagnetic transition temperature T-C gradually decreases due to reduction of paramagnetic Fe3+ to diamagnetic Fe2+, and the ferromagnetic transition is completely suppressed for Li-0.6(NiFe-PBA). On the other hand, T-C increases continuously as Li ion is extracted due to oxidation of diamagnetic Fe2+ to paramagnetic Fe3+, and the ferromagnetic transition is nearly recovered for Li-0(NiFe-PBA). Furthermore, the plots of T-C as a function of the amount of inserted/extracted Li ion x are well consistent with the theoretical values calculated by the molecular-field approximation.

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  • Effect of Nonmagnetic Substitution on the Magnetic Properties and Charge-Transfer Phase Transition of an Iron Mixed-Valence Complex, (n-C3H7)(4)N[(FeFeIII)-Fe-II(dto)(3)] (dto = C2O2S2)

    Hiromichi Ida, Atsushi Okazawa, Norimichi Kojima, Ryo Shimizu, Yasuhiro Yamada, Masaya Enomoto

    INORGANIC CHEMISTRY   51 ( 16 ) 8989 - 8996  2012.08  [Refereed]

     View Summary

    The iron mixed-valence complex (n-C3H7)(4)N[(FeFeIII)-Fe-II(dto)(3)] exhibits a novel type of phase transition called charge-transfer phase transition (CTPT), where the thermally induced electron transfer between Fe-II and Fe-III occurs reversibly at similar to 120 K, in addition to the ferromagnetic phase transition at T-C = 7 K. To investigate the mechanism of the CTPT, we have synthesized a series of magnetically diluted complexes (n-C3H7)(4)N[(Fe1-xZnxFeIII)-Zn-II-Fe-II(dto)(3)] (dto = C2O2S2; x = 0-1), and carried out magnetic susceptibility and dielectric constant measurements and Fe-57 Mossbauer spectroscopy. With increasing Zn-II concentration (x), the CTPT is gradually suppressed and disappears at x approximate to 0.13. On the other hand, the ferromagnetic transition temperature (T-C) is initially enhanced from 7 K to 12 K between x = 0.00 and 0.05, despite the nonmagnetic nature of Zn-II ions, and then it decreases monotonically from 12 K to 3 K with increasing Zn-II concentration. This anomalous dependence of T-C on Zn-II concentration is related to a change in the spin configuration of the ferromagnetic state caused by the partial suppression of the CTPT.

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  • K4Fe4P5O20: A New Mixed Valence Microporous Compound with Elliptical Eight-Ring Channels

    Zhangzhen He, Weilong Zhang, Wendan Cheng, Atsushi Okazawa, Norimichi Kojima

    INORGANIC CHEMISTRY   51 ( 14 ) 7469 - 7471  2012.07  [Refereed]

     View Summary

    A new small-pore compound K4Fe4P5O20 was obtained by conventional solid-state reaction in a closed crucible. The crystal structure is constructed by Fe4P5O20 units forming chains along the c axis and elliptical eight-ring channels on the a-b plane in which K cations locate inside. Such structural characteristics seem to be quite similar to those seen in the natrolite family. However, Fe ions in K4Fe4P5O20 have trigonal-bipyramidal instead of common tetrahedral coordination. Furthermore, our experimental results combined from magnetic susceptibility and Fe-57 Mossbauer spectrum measurements show mixed valence Fe3+/Fe2+ in the titled material. To the best of our knowledge, this is the first example that contains mixed valence iron ions in a so-called natrolite framework.

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  • Fabrication of a Cyanide-Bridged Coordination Polymer Electrode for Enhanced Electrochemical Ion Storage Ability

    Daisuke Asakura, Masashi Okubo, Yoshifumi Mizuno, Tetsuichi Kudo, Haoshen Zhou, Kazumichi Ikedo, Takashi Mizokawa, Atsushi Okazawa, Norimichi Kojima

    JOURNAL OF PHYSICAL CHEMISTRY C   116 ( 15 ) 8364 - 8369  2012.04  [Refereed]

     View Summary

    Host frameworks with the ability to store guest ions are very important in a wide range of applications including electrode materials for Li-ion batteries. In this report, we demonstrate that the ion storage ability of the cyanide-bridged coordination polymer (Prussian blue analogue, PBA) can be enhanced by suppressing vacancy formation. K-ions in the vacancy-suppressed PBA framework K1.72Mn[Mn(CN)(6)](0.93)center dot square(0.07).0.65H(2)O (square: a [Mn(CN)(6)](4-) defect) were electrochemically extracted. The open circuit voltages (OCVs) during K-ion extraction exhibited two specific plateaus at 3.0 and 3.7 V vs Li/Li+. Ex situ X-ray diffraction and IR spectroscopy revealed drastic structural and electronic changes during K-ion extraction. Furthermore, after K-ion extraction, the vacancy-suppressed PBA framework was applied to the cathode material for a Li-ion battery. The charge/discharge experiments revealed that the framework can accommodate a large amount of Li-ions.

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  • Study on the ferromagnetic state in iron mixed-valence complexes, A[(FeFeIII)-Fe-II(dto)(3)] (A = (n-CnH2n+1)(4)N; dto = C2S2O2) by means of Mossbauer spectroscopy

    Yuki Ono, Atsushi Okazawa, Masaya Enomoto, Norimichi Kojima

    HYPERFINE INTERACTIONS   207 ( 1-3 ) 139 - 143  2012.03  [Refereed]

     View Summary

    We have investigated the ferromagnetic states for (n-CnH2n+1)(4)N[(FeFeIII)-Fe-II(dto)(3)] (n = 3-6; dto = C2O2S2) by means of Fe-57 Mossbauer spectroscopy. The major component of the spin configuration in the ferromagnetic states for n = 3 and 4 is the low-temperature phase (LTP) with the Fe-III (S = 5/2) and FeII (S = 0) states. The high-temperature phase (HTP) of n = 4 remains by more than 20%, which is consistent with two ferromagnetic transitions (T-C = 7 & 13 K). Moreover, it was revealed that the Mossbauer spectra in the ferromagnetic states for n = 5 and 6 correspond to the HTP consisting of the Fe-II (S = 2) and Fe-III (S = 1/2) states.

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  • Oximato-bridged light-lanthanide Ln(4)Cu complexes showing ferromagnetic Ln-Cu exchange coupling

    Kei Fujiwara, Atsushi Okazawa, Norimichi Kojima, Go Tanaka, Shunsuke Yoshii, Hiroyuki Nojiri, Takayuki Ishida

    CHEMICAL PHYSICS LETTERS   530   49 - 54  2012.03  [Refereed]

     View Summary

    Heterometallic pentanuclear coordination compounds [Ln(4)(3+)Cu(2+)] involving light lanthanide ions, Ce, Pr, Nd, Sm, and Eu, were synthesized and structurally characterized. The exchange interactions between the Ln and Cu ions were evaluated by high-frequency electron paramagnetic resonance and magnetization studies, clarifying the presence of ferromagnetic exchange couplings in Nd-Cu (J(Nd-Cu)/k(B) = +0.30(6) K) and Sm-Cu (J(Sm-Cu)/k(B) = +2.08(3) K), very small couplings in Ce-Cu and Pr-Cu, and the absence in Eu-Cu. A significant chemical trend is found in the order of the atomic number. (C) 2012 Elsevier B. V. All rights reserved.

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  • Study on the spin-equilibrium and the succeeding magnetic phase transitions in the iron(III) μSR spectroscopy

    N. Kojima, K. Kagesawa, A. Okazawa, I. Watanabe

    RIKEN Accelerator Progress Report,   45   194  2012  [Refereed]

  • Size effect of intercalated cation on the charge transfer phase transition and ferromagnetism for iron mixed-valence system, A[FeIIFeIII(C2O2S2)3] (A = (CnH2n+1)4N, (CmH2m+1)3(CnH2n+1)N)

    N. Kojima, N. Kida, A. Okazawa, M. Enomoto

    Mössbauer Effect Reference and Data Journal   35   154 - 165  2012  [Refereed]  [Invited]

  • Exchange coupling in TbCu and DyCu single-molecule magnets and related lanthanide and vanadium analogs

    Takayuki Ishida, Ryo Watanabe, Kei Fujiwara, Atsushi Okazawa, Norimichi Kojima, Go Tanaka, Shunsuke Yoshii, Hiroyuki Nojiri

    DALTON TRANSACTIONS   41 ( 44 ) 13609 - 13619  2012  [Refereed]

     View Summary

    Heterometallic coordination compounds [Cu-II(L)(C3H6O)Ln(III)(NO3)(3)] and [(VO)-O-IV(L)(C3H6O)Ln(III)(NO3)(3)] (abbreviated as LnCu and LnV, respectively; H2L = N,N'-bis(3-methoxysalicylidene)-1,3-diamino-2,2-dimethylpropane; Ln = Gd, Tb, Dy, Ho, and Er) were synthesized, and the X-ray crystallographic analysis shows that their structures are isomorphous for each series. The single-molecule magnet behavior was observed for TbCu and DyCu, and the activation energies of magnetization reversal were 42.3(4) and 11.5(10) K, respectively. The magnetic exchange couplings in LnCu and LnV were precisely evaluated by means of combined high-frequency EPR and pulsed-field magnetization studies, to give J(Tb-Cu)/k(B) &gt;= 3.3 K, J(Dy-Cu)/k(B) = 1.63(1) K, J(Ho-Cu)/k(B) = 1.09(2) K, and J(Er-Cu)/k(B) = 0.24(1) K. A monotonic decrease of ferromagnetic J(Ln-Cu) was found in the order of the atomic number, Gd-64 to Er-68. The corresponding exchange parameters in LnV are smaller than those of the Cu derivatives, and J(Gd-V) was antiferromagnetic (-3.0 K determined from the magnetization jump). A possible mechanism for the exchange coupling and chemical trend is discussed.

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  • Ferromagnetic Exchange Couplings Showing a Chemical Trend in Cu-Ln-Cu Complexes (Ln = Gd, Tb, Dy, Ho, Er)

    Takashi Shimada, Atsushi Okazawa, Norimichi Kojima, Shunsuke Yoshii, Hiroyuki Nojiri, Takayuki Ishida

    INORGANIC CHEMISTRY   50 ( 21 ) 10555 - 10557  2011.11  [Refereed]

     View Summary

    Exchange couplings in isomorphous [LnCu(2)] were evaluated by high-frequency electron paramagnetic resonance and magnetization studies. The exchange parameter J(Ln-Cu) was decreased with an increase in the atomic, number; J(Ln-Cu)/k(B) = 4.45(11), 2.27(6), 0.902(10), 0.334(3), and 0.136(8) K for Ln = Gd, Tb, Dy, Ho, and Er, respectively.

    DOI PubMed CiNii

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  • Single-molecule magnet behavior enhanced by magnetic coupling between 4f and 3d spins

    Atsushi Okazawa, Hiroyuki Nojiri, Takayuki Ishida, Norimichi Kojima

    POLYHEDRON   30 ( 18 ) 3140 - 3144  2011.11  [Refereed]

     View Summary

    We synthesized and characterized a new compound [{Dy(hfac)(3)}(2)Pd(dpk)(2)] ([Dy(2)Pd]; Hdpk = di-2-pyridyl ketoxime), which is isostructural with the known [Dy(2)Cu] and [Dy(2)Ni]. The study of the [Dy(2)Pd] compound containing diamagnetic Pd ion is indispensable to clarify a contribution of the exchange coupling for a 4f-3d single-molecule magnet behavior. From the ac susceptibility measurements on [Dy(2)Pd], we obtained Delta/k(B) = 28.6(11) K and T(B) = 1.1 K. In accordance with the blocking behavior, the pulsed-field magnetization showed the hysteresis behavior below 1.1 K. These parameters on [Dy(2)Pd] having S(Pd) = 0 was compared with those of the derivatives having S(Cu) = 1/2 (Delta/k(B) = 47 K and T(B) = 1.8 K) and S(Ni) = 1 (Delta/k(B) = 62(4) K and T(B) = 2.5 K). The T(B) and Delta steadily increase with the increasing 3d(4d) spin quantum number. (C) 2011 Elsevier Ltd. All rights reserved.

    DOI

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  • Exchange couplings in one-dimensionally arrayed 4f-3d heterometallic [Ln(2)Cu(2)](n) compounds: A chemical trend of the coupling parameter

    Atsushi Okazawa, Kei Fujiwara, Ryo Watanabe, Norimichi Kojima, Shunsuke Yoshii, Hiroyuki Nojiri, Takayuki Ishida

    POLYHEDRON   30 ( 18 ) 3121 - 3126  2011.11  [Refereed]

     View Summary

    Heterometallic polymeric coordination compounds [(Ln(hfac)(2)(CH3OH)}(2){Cu(dmg)(Hdmg)}(2)](n) (abbreviated as [Ln(2)Cu(2)](n)) involving light lanthanoid ions, Pr, Nd, Sm, and Eu, were synthesized, where H(2)dmg and Hhfac stand for dimethylglyoxime and 1,1,1,5,5,5-hexafluoropentane-2,4-dione, respectively. The X-ray crystallographic analysis shows that their structures are isomorphous to those of the known heavy lanthanoid analogs. The exchange couplings were evaluated by high-frequency electron paramagnetic resonance and pulsed-field magnetization studies, giving ferromagnetic exchange parameters: J(Pr-cu)/k(B) = 0.039(1) K, J(Nd-cu)/k(B) = 0.38(1) K, J(sm-cu)/k(B) = 0.95(2) K, and no interaction between Eu and Cu ions. A significant trend is found in the order of the periodic table. The ferro- and antiferromagnetic 4f-3d couplings were characterized for the light and heavy lanthanoid derivatives, respectively. The magnitude of J(Ln-Cu) decreases with a decrease of the 4f-spin portion. i.e., the number of unpaired electrons, whether the coupling is ferro- or antiferromagnetic. (C) 2011 Elsevier Ltd. All rights reserved.

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  • Study on the spin-crossover transition in [Fe(cis-/trans-stpy)(4)(X)(2)] (stpy: styrylpyridine, X: NCS, NCBH3) under high pressure toward ligand-driven light-induced spin change

    Akira Sugahara, Kimio Moriya, Masaya Enomoto, Atsushi Okazawa, Norimichi Kojima

    POLYHEDRON   30 ( 18 ) 3127 - 3130  2011.11  [Refereed]

     View Summary

    Toward the realization of a ligand-driven light-induced spin change (LD-LISC) around room temperature, we have investigated the spin-crossover phenomenon in [Fe(stpy)(4)(X)(2)] (stpy = styrylpyridine, X = NCS, NCBH3) under high pressure. The spin transition temperature increases from 110 to 220 K with increasing applied pressure up to 0.75 GPa for [Fe(trans-stpy)(4)(NCS)(2)], while [Fe(cis-stpy)(4)(NCS)(2)] shows the high-spin state in the temperature region between 2 and 300 K even at 0.75 GPa. In the case of X = NCBH3, due to the stronger ligand field of NCBH3, the spin transition temperature increases from 240 to 360 K with increasing applied pressure up to 0.50 GPa for [Fe(trans-stpy)(4)(NCBH3)(2)]. In the case of [Fe(cis-stpy)(4)(NCBH3)(2)], the spin state is the high-spin state in the temperature region between 2 and 300 K. However, the spin transition appears at 125 K under 0.5 GPa and the transition temperature increases with increasing applied pressure. In this way, we have decided the applied pressure region of 0.65-1.09 GPa where [Fe(stpy)(4)(NCBH3)(2)] undergoes LD-LISC at room temperature. (C) 2011 Elsevier Ltd. All rights reserved.

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  • Development of pH-Sensitive Spin-crossover Iron(II) Complex Films, [Fe-II(diAMsar)]-Nafion: Manipulation of the Spin State by Proton Concentration

    Hajime Kamebuchi, Taketomo Jo, Hideharu Shimizu, Atsushi Okazawa, Masaya Enomoto, Norimichi Kojima

    CHEMISTRY LETTERS   40 ( 8 ) 888 - 889  2011.08  [Refereed]

     View Summary

    We newly synthesized transparent films composed of pH-sensitive spin-crossover complex [Fe-II(diAMsar)] (diAMsar: 1,8-diaminosarcophagine) and an ion-exchange polymer, Nafion, having different colors corresponding to proton concentration. The UV-vis spectroscopic measurements revealed that the films, which were provided under pH 4, 7, and 10 conditions, showed the spin state depending on pH.

    DOI J-GLOBAL

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  • Unusually Large Magnetic Anisotropy in a CuO-Based Semiconductor Cu5V2O10

    Zhangzhen He, Chensheng Lin, Wendan Cheng, Atsushi Okazawa, Norimichi Kojima, Jun-ichi Yamaura, Yutaka Ueda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   133 ( 5 ) 1298 - 1300  2011.02  [Refereed]

     View Summary

    A CuO-based material Cu5V2O10 was successfully grown in a closed crucible using Sr(OH)(2)center dot 8H(2)O as flux. The structure of Cu5V2O10 can be viewed as being composed of two types of zigzag Cu-O chains running along the b- and c-axes, which shows a two-dimensional crosslike framework with 12-column square tunnels along the a-axis. Magnetic measurements show that Cu5V2O10 exhibits unexpected large magnetic anisotropy, which is the first time magnetic anisotropy energy of similar to 10(7) erg/cm(3) in the CuO-based materials has been observed. The origins of large anisotropy are suggested to arise from strong anisotropic exchanges due to the particular bonding geometry and the Jahn-Teller distortion of Cu2+ ions. Further, the band structure investigated by the GGA+U method suggests that Cu5V2O10 is a semiconductor.

    DOI PubMed

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    19
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  • Chemical trend of Ln-M exchange couplings in heterometallic complexes with Ln = Gd, Tb, Dy, Ho, Er and M = Cu, V

    Ryo Watanabe, Kei Fujiwara, Atsushi Okazawa, Go Tanaka, Shunsuke Yoshii, Hiroyuki Nojiri, Takayuki Ishida

    CHEMICAL COMMUNICATIONS   47 ( 7 ) 2110 - 2112  2011  [Refereed]

     View Summary

    The 4f-3d exchange couplings were definitively and precisely determined in the dinuclear complexes (Ln-M) involving double mu-oxo-bridges, by means of combined high-frequency electron paramagnetic resonance and pulsed-field magnetization techniques, revealing a monotonic decrease of ferromagnetic J(Ln-Cu) in the order of the atomic number, (64)Gd to (68)Er.

    DOI PubMed CiNii

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    49
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  • Ion-Induced Transformation of Magnetism in a Bimetallic CuFe Prussian Blue Analogue

    Masashi Okubo, Daisuke Asakura, Yoshifumi Mizuno, Tetsuichi Kudo, Haoshen Zhou, Atsushi Okazawa, Norimichi Kojima, Kazumichi Ikedo, Takashi Mizokawa, Itaru Honma

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   50 ( 28 ) 6269 - 6273  2011  [Refereed]

    DOI PubMed

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  • Ferromagnetic Gd-Cu, Tb-Cu, and Ho-Cu Couplings in Isomorphous [Ln(2)Cu] Complexes

    Atsushi Okazawa, Ryo Watanabe, Masaru Nezu, Takashi Shimada, Shunsuke Yoshii, Hiroyuki Nojiri, Takayuki Ishida

    CHEMISTRY LETTERS   39 ( 12 ) 1331 - 1332  2010.12  [Refereed]

     View Summary

    Exchange couplings in [{Ln(hfac)(3)}(2)Cu(dpk)(2)] (Hdpk stands for di 2-pyridyl ketoxime) were evaluated by high-frequency electron paramagnetic resonance and magnetization studies, showing ferromagnetic Ln-Cu couplings with J(Ln-Cu)/k(B) = +1 271(7), +0 405(3), and +0 196(13) K for Ln Gd Tb, and Ho, respectively

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  • Spin-Transition-Like Behavior on One Side in a Nitroxide-Copper(II)-Nitroxide Triad System

    Atsushi Okazawa, Takayuki Ishida

    INORGANIC CHEMISTRY   49 ( 21 ) 10144 - 10147  2010.11  [Refereed]

     View Summary

    The ground spin-state of [Cu(phpyNO)(2)(H(2)O)(2)](BF(4))(2) was switched between S(total) = 1/2 and 3/2 across 175 K. On warming, the space group was changed from P2(1)2(1)2(1) to C222(1) in a single-crystal-to-single-crystal manner, and the transient structure could be monitored by means of the crystallographic analysis. The copper-radical exchange coupling changed from 2J/k(B) = -463(3) to +312(6) K with rather small Cu-O-N-C(2py) twisting deformation on one side, while practically no distortion occurred on the other.

    DOI PubMed CiNii

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  • Ferro- and Antiferromagnetic Coupling Switch Accompanied by Twist Deformation around the Copper(II) and Nitroxide Coordination Bond

    Atsushi Okazawa, Daisuke Hashizume, Takayuki Ishida

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   132 ( 33 ) 11516 - 11524  2010.08  [Refereed]

     View Summary

    Two novel copper(II) complexes with tert-butyl 2-pyridyl nitroxide (2pyNO(center dot)), [Cu(2+)(2pyNO(-))(2PyNO(center dot))](2)(BF(4)(-))(2)(1 center dot BF(4)) and [Cu(2+)(2pyNO(-))(2pyNO(center dot))](2)(ClO(4)(-))(2)(1 center dot ClO(4)), were prepared and structurally characterized. They contained mixed-valent ligands from 2pyNO, whose oxygen atoms were located at equatorial positions of the copper ion. The [Cu(2+)(2pyNO(-))(2pyNO(center dot))] unit was dimerized by mu-oxo bridges of the anion ligand, giving a zigzag linear spin system involving four paramagnetic S = 1/2 centers. The two compounds are isomorphous in an orthorhombic Pbca space group. Magnetic study revealed that 1 center dot ClO(4) showed ferromagnetic copper-radical coupling in all temperature ranges investigated here. On the other hand, 1 center dot BF(4) exhibited a structural phase transition at 64 K, where the magnetic susceptibility was drastically dropped on cooling. The copper-radical magnetic couplings were characterized as ferro- and antiferromagnetic for the high- and low-temperature phases, respectively. The crystallographic analysis clarified that the nitroxide oxygen atom remained at the equatorial position throughout the single-crystal-to-single-crystal phase transition, while the previously known spin-transition-like copper-radical compounds showed conversion of the roles of equatorial and axial positions. The orthogonal arrangement between the copper d sigma and nitroxide pi(star) orbitals is essential for the ferromagnetic coupling, and a slight dislocation of the radical oxygen atom from the chelate plane leads to violation of the orthogonal orbital arrangement, giving a practically diamagnetic low-temperature phase.

    DOI PubMed CiNii

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  • Study on the Rapid Spin Equilibrium in Ph4P[ZnIIFeIII(mto)3] (mto = Monothiooxalato)

    Koichi Kagesawa, Atsushi Okazawa, Masaya Enomoto, Norimichi Kojima

    CHEMISTRY LETTERS   39 ( 8 ) 872 - 873  2010.08  [Refereed]

     View Summary

    We synthesized a mto (= monothiooxalato)-bridged heterometal complex, Ph4P[(ZnFeIII)-Fe-II(mto)(3))] consisting of (FeO3S3)-O-III and (ZnO6)-O-II octahedra and investigated its physical properties. Ph4P[(ZnFeIII)-Fe-II(mto)(3)] has a two-dimensional honeycomb network structure. The ESR and Fe-57 Mossbauer spectra revealed that the rapid spin equilibrium in which the high-spin (HS) state and the low-spin (LS) state exchange in the time scale of 10(-10) &lt; tau &lt; 10(-7)s occurs at the (FeO3S3)-O-III site, which is the first report for an assembled metal complex system.

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  • Super-superexchange coupling through a hydrogen bond in a linear copper(II) complex, [Cu(LH)(L)]center dot BF4 center dot 2H(2)O (LH = N-tert-butyl-N-2-pyridylhydroxylamine)

    Atsushi Okazawa, Takayuki Ishida

    CHEMICAL PHYSICS LETTERS   480 ( 4-6 ) 198 - 202  2009.10  [Refereed]

     View Summary

    Crystal structure analysis of the title compound revealed the presence of a hydrogen bond in an intermolecular LH center dot center dot center dot L contact with the O center dot center dot center dot O distance of 2.4252(16) angstrom to form a one-dimensional polymeric structure. Magnetic study clarified that a relatively large exchange coupling was determined as 2J/k(B) = -33.2(2) K from the Bonner-Fisher analysis and ascribable to the super-superexchange coupling along the Cu-O-H center dot center dot center dot O-Cu path. (C) 2009 Elsevier B.V. All rights reserved.

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  • Magnetic properties and exchange couplings of one-dimensionally arrayed 4f-3d heterometallic [Ln(2)Cu(2)](n) compounds

    Atsushi Okazawa, Ryo Watanabe, Hiroyuki Nojiri, Takashi Nogami, Takayuki Ishida

    POLYHEDRON   28 ( 9-10 ) 1808 - 1813  2009.06  [Refereed]

     View Summary

    Heterometallic polymeric coordination compounds [{Ln(hfac)(2)(CH3OH)}(2){Cu(dmg)(Hdmg)}(2)](n) ([Ln(2)Cu(2)](n); Ln = Tb, Ho, and Er; H(2)dmg = dimethylglyoxime; Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) were synthesized, and the X-ray crystallographic analysis shows that their structures are isomorphous to those of the known ferrimagnetic [Gd2Cu2](n) and [Dy2Cu2](n) analogs. The exchange couplings in [Tb2Cu2](n), [Ho2Cu2](n), and [Er2Cu2](n) were precisely evaluated by high-frequency EPR and pulsed-field magnetization studies, giving J(Tb-Cu)/k(B) = -0.77(2)K, J(Ho-Cu)/k(B) = -0.250(12)K and J(Er-Cu)/k(B) = -0.149(15) K. They were comparable to those of the Gd and Dy analogs. The absolute value of the exchange coupling parameter monotonically decreases in the order of Gd, Tb, Dy, Ho, and Er. (C) 2008 Elsevier Ltd. All rights reserved.

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  • Strong intramolecular ferromagnetic couplings in nickel(II) and copper(II) complexes chelated with tert-butyl 5-methoxy-2-pyridyl nitroxide

    Atsushi Okazawa, Takashi Nogami, Takayuki Ishida

    POLYHEDRON   28 ( 9-10 ) 1917 - 1921  2009.06  [Refereed]

     View Summary

    We successfully isolated a new paramagnetic bidentate ligand tert-butyl 5-methoxy-2-pyridyl nitroxide (meopyNO). Complexation of nickel(II) and copper(II) perchlorates with meopyNO gave the corresponding ML(2)-type bis-chelated compounds. The magnetic studies showed that they were ground high-spin molecules with 2J/k(B) = +288(5) and +178(3) K for [M(meopyNO)(2)(H(2)O)(2)]center dot(ClO(4))(2) (M = Ni and Cu, respectively), where the spin Hamiltonian is defined as H = -2J(S(1)center dot S(2) + S(2)center dot S(3)). From the crystallographic analysis, the torsion angles (phi) around M-O-N-C(2py) were 4.2(3)degrees and 6.87(19)degrees, respectively, being so small that the orthogonality between the magnetic radical pi* and the metal d sigma orbitals would be guaranteed. (C) 2008 Elsevier Ltd. All rights reserved.

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  • Ferromagnetic Dy-Ni and Antiferromagnetic Dy-Cu Couplings in Single-Molecule Magnets [Dy2Ni] and [Dy2Cu] (vol 47, pg 9763, 2008)

    Atsushi Okazawa, Takashi Nogami, Hiroyuki Nojiri, Takayuki Ishida

    INORGANIC CHEMISTRY   48 ( 7 ) 3292 - 3292  2009.04  [Refereed]

     View Summary

    &lt;B&gt;[Correction]&lt;/B&gt;

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  • Ferromagnetic Dy-Ni and Antiferromagnetic Dy-Cu Couplings in Single-Molecule Magnets [Dy2Ni] and [Dy2Cu]

    Atsushi Okazawa, Takashi Nogami, Hiroyuki Nojiri, Takayuki Ishida

    INORGANIC CHEMISTRY   47 ( 21 ) 9763 - 9765  2008.11  [Refereed]

     View Summary

    The exchange couplings in [{Dy(hfac)(3)}(2)Cu(dpk)(2)] and [{Dy(hfac)(3)}(2)-Ni(dpk)(2)(py)(2)] (Hdpk = di-2-pyridyl ketoxime) were precisely evaluated by high-frequency electron paramagnetic resonance and pulsed-field magnetization studies, giving J(Dy-Cu)/k(B) = -0.126 K and J(Dy-Ni)/k(B) = +0.031 K.

    DOI PubMed CiNii

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  • Magneto-structure relationship in copper(II) and nickel(II) complexes chelated with stable tert-butyl 5-phenyl-2-pyridyl nitroxide and related radicals

    Atsushi Okazawa, Yasunori Nagaichi, Takashi Nogami, Takayuki Ishida

    INORGANIC CHEMISTRY   47 ( 19 ) 8859 - 8868  2008.10  [Refereed]

     View Summary

    We have isolated and characterized a new paramagnetic bidentate ligand, tert-butyl 5-phenyl-2-pyridyl nitroxide (phpyNO). The spin distribution onto the pyridine ring was clarified from the Electron Spin Resonance spectrum. Complexation of phpyNO with nickel(II) and copper(II) ions gave ML2-type chelated compounds. The magnetic measurements of [Ni(phpyNO)(2)(H2O)(2)]center dot(ClO4)(2) and [Cu(phpyNO)(2)(H2O)]center dot(ClO4)(2)center dot C6H4Cl2 revealed that the metalradical exchange couplings were ferromagnetic with 2J/k(B) = +409(10) and +434(12) K, respectively. The torsion angle (phi) around M-O-N-C-2py can be regarded as a reliable indicator for the plane geometry of chelates; namely, highly planar chelates defined by small phi exhibit ferromagnetic coupling. An approximate linear relation. was found in the J versus phi plot using the data of the present complexes and. related known compounds. The critical angle of phi, at which the sign of the metal-radical exchange changes from positive to negative, was 12.6(9)degrees. This finding could be almost reproduced by density-functional theory calculation on a model copper(II)-nitroxide dyad. The exchange couplings in equatorially coordinated copper(II)- and nickel(II)-nitroxide complexes are very strongly ferromagnetic by nature.

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  • Exchange coupling and energy-level crossing in a magnetic chain [Dy2Cu2](n) evaluated by high-frequency electron paramagnetic resonance

    Atsushi Okazawa, Takashi Nogami, Hiroyuki Nojiri, Takayuki Ishida

    CHEMISTRY OF MATERIALS   20 ( 9 ) 3110 - 3119  2008.05  [Refereed]

     View Summary

    A 4f - 3d heterometallic polymeric coordination compound [[Dy(hfac)(2)(CH3OH)}(2)(Cu(dmg)(Hdmg)(2)}](n) [(Dy2Cu](n) Hdmg = dimethylglyoxime; Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) was synthesized, and the X-ray crystallographic analysis shows that the structure is isomorphous to the known ferrimagnetic [Gd2Cu2)](n) polymer. A centrosymmetric diamond-arrayed ferrimagnetic unit involving the oximate bridge, Dy - O - N - Cu, is repeated to form a discrete chain. An onset of the frequency dependence was found in the ac magnetic susceptibility measurements down to 1.8 K. Low-temperature magnetization measurements on [Dy2Cu2](n) exhibited magnetic hysteresis with magnetization steps. To examine the energy level structure and the exchange coupling between the Dy and Cu ions, high-frequency EPR (HF-EPR) spectra of a polycrystalline sample of [Dy2Cu2](n) were recorded at various frequencies (34.7 - 525.4 GHz) and temperatures. We analyzed the spectra by treating the Dy moments as Ising spins and built an exchange-coupling model for a diamond-arrayed tetranuclear macrocycle [Dy2Cu2]. The Dy - Cu exchange couplings were precisely evaluated, owing to the high resolution of HF-EPR; J/k(B) = - 0.895(8) and - 0.061(8) K for two independent Dy - Cu relations, where the exchange parameter is defined as - J. The Cu center dot center dot center dot Cu coupling among the macrocycles was estimated to be ferromagnetic with approximately 1 K. The present study has established the definitive methodology to examine the energy level in 4f - 3d heterometallic systems by using HF-EPR. The magnetic properties of the [Dy2Cu2](n) chain were plausibly described as a perturbed system of a single-molecule magnet. The quantum tunneling of the magnetization is based on a different principle compared with those of the 3d-based single-molecule magnets, since the energy level structure of [Dy2Cu2](n) is regulated by the exchange couplings.

    DOI CiNii

  • Tetranuclear heterometallic cycle Dy2Cu2 and the corresponding polymer showing slow relaxation of magnetization reorientation

    Sohei Ueki, Atsushi Okazawa, Takayuki Ishida, Takashi Nogami, Hiroyuki Nojiri

    POLYHEDRON   26 ( 9-11 ) 1970 - 1976  2007.06  [Refereed]

     View Summary

    We prepared tetranuclear complexes [{Cu(emg)(Hemg)(ROH)}(2)Dy(hfac)(2)(ROH)}(2)] (abbreviated as [Dy2Cu2]-R; R = Me, Et; H(2)emg=ethylmethylglyoxime) and the corresponding polymer [{Cu(dmg)(Hdmg)}(2){Dy(hfac)(2)(CH3OH)}(2)](n) center dot 2(MeOH) ([Dy2Cu2](n); H(2)dmg = dimethylglyoxime), which were characterized as analogs of the known [Gd2Cu2] monomer and polymer, respectively, by means of X-ray crystallographic analysis. The M-H curves clarified antiferromagnetic coupling between Dy and Cu in the [Dy2Cu2] motif, leading to the Dy magnetic moments aligned parallel ([Cu(down arrow)Dy(up arrow)Cu(down arrow)Dy(up arrow)]). Ac magnetic susceptibility measurements of [Dy2Cu2]-Me and [Dy2Cu2](n), exhibited a chi(ac)' (in-phase) decrease and a concomitant chi('')(ac) (out-of-phase) increase with an increase of frequency. Low-temperature magnetization measurements on [Dy2Cu2], exhibited magnetic hysteresis, which is characteristic of single-chain magnets. (c) 2006 Elsevier Ltd. All rights reserved.

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  • Preparation, structures, and magnetic properties of precursors for chelating compounds of 2-pyridyl nitroxide derivatives

    Atsushi Okazawa, Takashi Nogami, Takayuki Ishida

    POLYHEDRON   26 ( 9-11 ) 1965 - 1969  2007.06  [Refereed]

     View Summary

    We successfully synthesized and characterized two precursors for paramagnetic chelating ligands, N-p-anisyl-N-2-pyridylhydroxyl-amine and 2,6-bis(N-t-butylhydroxylamino)pyridine. The former can be regarded as a rare case since N,N-diarylhydroxylamines cannot be isolated in general because of facile autoxidation. The oxidation with silver(I) oxide gave radicals showing typical nitroxide ESR signals, but the resultant radicals were unstable under ambient conditions. Theoretical DFT calculation indicated that the bisnitroxide radical, pyridine-2,6-diyl bis(t-butyl nitroxide), had a triplet ground state. (c) 2006 Elsevier Ltd. All rights reserved.

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  • tert-butyl 2-pyridyl nitroxide available as a paramagnetic chelate ligand for strongly exchange-coupled metal-radical compounds

    Atsushi Okazawa, Takashi Nogami, Takayuki Ishida

    CHEMISTRY OF MATERIALS   19 ( 11 ) 2733 - 2735  2007.05  [Refereed]

    DOI CiNii

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  • Strong ferromagnetic exchange couplings in copper(II) and nickel(II) complexes with a paramagnetic tridentate chelate ligand, 2,2 '-bipyridin-6-yl tert-butyl nitroxide

    Keita Osanai, Atsushi Okazawa, Takashi Nogami, Takayuki Ishida

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   128 ( 43 ) 14008 - 14009  2006.11  [Refereed]

    DOI PubMed CiNii

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  • Ferromagnetic exchange coupling in a spiro-fused dinuclear nickel(II) complex with an approximate D-2d symmetry

    Atsushi Okazawa, Takashi Nogami, Takayuki Ishida

    CHEMICAL PHYSICS LETTERS   427 ( 4-6 ) 333 - 337  2006.08  [Refereed]

     View Summary

    Ferromagnetic exchange coupling was operative between nickel(II) spins in a dinuclear nickel(II) complex [{Ni(hfac)(2)}(2)(py(4)C)] with J/k(B) = +0.57(2)K (H = -2JS(1) . S-2), where hfac and py(4)C Stand for 1,1,1,5,5,5-hexafluoropentane-2,4-dionate and tetrakis(2-pyridyl)methane, respectively. X-ray crystal structure analysis revealed an approximate D-2d symmetry of the [Ni(py4C)Ni] core and accordingly the orthogonal arrangement between the two coordination basal planes. Mechanism of the ferromagnetic coupling was proposed on the basis of the orthogonal d sigma-type magnetic orbitals, which was supported by DFT calculation. (c) 2006 Elsevier B.V. All rights reserved.

    DOI CiNii

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  • Structures and magnetic properties of copper(II) complexes containing tetrakis(2-pyridyl)methane

    A Okazawa, T Ishida, T Nogami

    POLYHEDRON   24 ( 16-17 ) 2584 - 2587  2005.11  [Refereed]

     View Summary

    We designed spiro-fused dinculear complexes using tetrakis(2-pyridyl)methane (py(4)C) for the development of ground high-spin molecules. We attempted to prepare a dinuclear copper(II) complex [{Cu(hfac)(2)}(2)(py(4)C)], where hfac stands for 1, 1,1,5,5,5-hexafluoropentane-2,4-dionate, but we obtained [Cu(hfac)(2)(py(4)C)] and [Cu(hfac)(py(4)C) (.) Cu(hfac)(3)]. These molecular structures were determined by the X-ray crystal structure analysis. (c) 2005 Elsevier Ltd. All rights reserved.

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  • Dinuclear manganese(II) complex containing tetrakis(2-pyridyl)methane as a spiro-fused bridge

    A Okazawa, T Ishida, T Nogami

    CHEMISTRY LETTERS   33 ( 11 ) 1478 - 1479  2004.11  [Refereed]

     View Summary

    A dinuclear manganese(II) complex [{Mn(hfac)(2)}(2)(py(4)C)] was synthesized, where hfac and py(4)C denote 1,1,1,5,5,5-hexafluoropentane-2,4-dionate and tetrakis(2-pyridyl)methane, respectively. X-Ray crystallographic analysis revealed that the dihedral angle was 87.4(2)degrees between two chelate rings around the spiro center. Very weak antiferromagnetic interaction is operative between manganese(II) spins.

    DOI CiNii

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Books and Other Publications

  • Modern Mössbauer Spectroscopy : New Challenges Based on Cutting-Edge Techniques

    Yoshida, Yutaka, Langouche, Guido

    Springer  2021 ISBN: 9789811594212

  • 錯体化合物事典

    錯体化学会

    朝倉書店  2019 ISBN: 9784254141054

Presentations

  • Improvement of solubility by asymmetrizing terpyridine iron complexes and its application to catholytes of redox flow batteries

    Takayuki Kakuchi, Atsushi Okazawa, Kosuke Kawai, Masashi Okubo

    Presentation date: 2023.09

    Event date:
    2023.09
     
     
  • Kinetically controlled self-assembly of Rh(II) squares assisted by monotopic ligand

    Naoki Sanada, Atsushi Okazawa, Satoshi Takahashi, Hirofumi Sato, Shuichi Hiraoka

    Presentation date: 2023.09

    Event date:
    2023.09
     
     
  • 結晶構造解析とDFT計算による鉄混合原子価錯体(n-C3H7)4N[FeIIFeIII(dto)3]の光誘起電荷移動相転移の可能性の検討

    糸井 充穂, 岡澤 厚, 山浦 淳一, 真木 祥千子, 小松 徳太郎, Isabelle Maurin, Epiphane Codjovi, Kamel Boukheddaden, 小島 憲道

    日本物理学会第74回年次大会  (九州大学伊都キャンパス(福岡県福岡市)) 

    Presentation date: 2019.03

  • ジアリールコバト二価錯体の合成と反応

    管野 公平, 岡澤 厚, 松尾 司

    日本化学会第99春季年会  (甲南大学岡本キャンパス(兵庫県神戸市)) 

    Presentation date: 2019.03

  • Spin dynamics in tripyrazolylmethane iron(II) complexes showing static and dynamic spin-crossover phenomena

    A. Okazawa, H. Kobayashi, I. Kawasaki, I. Watanabe, N. Kojima

    The 9th TOYOTA RIKEN International Workshop on New Developments and Prospects for Futrue of Mössbauer Spectroscopy (IWMS2018)  (Toyota Commemorative Museum of Industry and Technology (Nagoya, Japan)) 

    Presentation date: 2018.11

  • Comparison of μSR Spectra for Tripyrazolylmethane Iron(II) Spin-Crossover Complexes to Investigate Spin Dynamics

    A. Okazawa, H. Kobayashi, I. Watanabe, I. Kawasaki, N. Kojima

    2nd RIKEN SyMPOSIUM  (Prama Sanur Beach Bali Hotel (Bali, Indonesia)) 

    Presentation date: 2018.11

  • Magneto-Structural Relationship on Metal Complexes Using Dual Radical Chelate Ligand Showing Ground Triplet State

    A. Okazawa, T. Ishida, N. Kojima

    43rd International Conference on Coodination Chemistry (ICCC2018)  (Sendai International Conference Center (Sendai, Japan)) 

    Presentation date: 2018.08

  • Crystal structure construction of organic salts comprising proton, H+, as a counter cation

    R. Tanaka, A. Okazawa, N. Kojima, N. Matsushita

    Presentation date: 2018.03

  • ジチオオキサラト架橋ヘテロ金属錯体の光照射下での磁気挙動

    永峰 翔太, 榎本 真哉, 岡澤 厚

    日本化学会第98春季年会  (日本大学理工学部船橋キャンパス(千葉県船橋市)) 

    Presentation date: 2018.03

  • ターピリジン誘導体を配位子とするIr錯体の光水素発生反応における増感特性

    加藤 天, 生田 直也, 岡澤 厚, 滝沢 進也, 村田 滋

    日本化学会第98春季年会  (日本大学理工学部船橋キャンパス(千葉県船橋市)) 

    Presentation date: 2018.03

  • クマリン誘導体を配位子とするイリジウム錯体の合成と光増感一重項酸素発生への応用

    宮岸 優奈, 生田 直也, 岡澤 厚, 滝沢 進也, 村田 滋

    日本化学会第98春季年会  (日本大学理工学部船橋キャンパス(千葉県船橋市)) 

    Presentation date: 2018.03

  • バナジウム希釈系混合原子価鉄錯体(n-C3H)4N[FeIIFeIII1-xVIIIx(C2O2S2)3]の誘電測定による電荷移動挙動の検出

    川本 史仁, 志田 典浩, 岡澤 厚, 小島 憲道, 榎本 真哉

    日本化学会第98春季年会  (日本大学理工学部船橋キャンパス(千葉県船橋市)) 

    Presentation date: 2018.03

  • 基底三重項を示すデュアルラジカキレート配位子用いた金属錯体の合成、構造および磁性

    岡澤 厚, 石田 尚行, 小川 桂一郎, 小島 憲道

    錯体化学会第67回討論会  (北海道大学札幌キャンパス(北海道札幌市)) 

    Presentation date: 2017.09

  • Syntheses and Magnetic Properties of Linear Two-Coordinated Iron(II) and Iron(I) Complexes

    A. Okazawa, T. Matsuo, Y. Kobayashi  [Invited]

    International Conference on the Applications of the Mössbauer Effect (ICAME2017)  (Azimut Hotel (Saint-Petersburg, Russia)) 

    Presentation date: 2017.09

  • Enhanced Magnetism of Perovskite Oxides, Sr(Sn,Fe)O3-δ, by Substitution of Non-Magnetic Ca and Ti ions

    K. Nomura, S. Suzuki, T. Mizunuma, Y. Koike, A. Okazawa

    International Conference on the Applications of the Mössbauer Effect (ICAME2017)  (Azimut Hotel (Saint-Petersburg, Russia)) 

    Presentation date: 2017.09

  • 57Fe and 119Sn Mossbauer Study of SrSnO3 Doped with Fe and Sb

    K. Nomura, S. Suzuki, Y. Koike, A. Okazawa, Y. Kobayashi, M. Kaneko

    International Conference on the Applications of the Mössbauer Effect (ICAME2017)  (Azimut Hotel (Saint-Petersburg, Russia)) 

    Presentation date: 2017.09

  • Control of Charge Transfer Phase Transition and Ferromagnetism for Iron Mixed-valence Complexes by Means of Photo-isomerization

    N. Kojima, J. Yoshida, A. Okazawa, M. Enomoto, Y. Kobayashi

    International Conference on the Applications of the Mössbauer Effect (ICAME2017)  (Azimut Hotel (Saint-Petersburg, Russia)) 

    Presentation date: 2017.09

  • Rind配位子を用いた直線二配位鉄(I)錯体の動的スピン挙動

    岡澤 厚, 二階 正憲, 羽村 将宏, 合田 舜, 早川 直輝, 松尾 司

    日本化学会第97春季年会  (慶應義塾大学日吉キャンパス(神奈川県横浜市)) 

    Presentation date: 2017.03

  • CaおよびTiの置換によるSr(Sn,Fe)O3の磁気特性とMössbauerスペクトル

    水沼 丈也, 鈴木 茂世, 小池 裕也, 野村 貴美, 岡澤 厚

    第18回メスバウアー分光研究会シンポジウム  (東京理科大学森戸記念館(東京都新宿区)) 

    Presentation date: 2017.03

  • ビピリジン骨格を有する有機アクセプター分子と鉄錯体ドナーからなるベイポクロミック電荷移動塩における構造未知相の粉末X線構造解析

    田中 李叶子, 小中 尚, 佐々木 明登, 岡澤 厚, 小島 憲道, 松下信之

    日本結晶学会平成28年度年会  (茨城県立県民文化センター(茨城県水戸市)) 

    Presentation date: 2016.11

  • Magneto-Structural Relationship on Strong Exchange Interactions between Chelating Radical and Transition-Metal Spins

    A. Okazawa  [Invited]

    The 4th International Conference on Advanced Materials Science and Technology (ICAMST2016)  (Universitas Negeri Malang (Malang, Indonesia)) 

    Presentation date: 2016.09

  • ビピリジン骨格を有する有機アクセプターと鉄錯体ドナーからなる電荷移動塩における固相合成相の結晶構造

    田中 李叶子, 岡澤 厚, 小島 憲道, 松下 信之

    第25回有機結晶シンポジウム  (京都大学吉田南キャンパス(京都府京都市)) 

    Presentation date: 2016.09

  • 鎖状二価カチオンがもたらす鉄混合原子価錯体における磁性層の歪みによる電荷移動挙動の変化

    矢口 寛, 佐々木 翔太郎, 榎本 真哉, 岡澤 厚, 小島 憲道

    錯体化学会第66回討論会  (福岡大学七隈キャンパス(福岡県福岡市)) 

    Presentation date: 2016.09

  • ベイポクロミック鉄錯体電荷移動塩の粉末X線構造解析による結晶構造解明

    田中 李叶子, 小中 尚, 佐々木 明登, 岡澤 厚, 小島 憲道, 松下信之

    錯体化学会第66回討論会  (福岡大学七隈キャンパス(福岡県福岡市)) 

    Presentation date: 2016.09

  • Magnetic Properties of V-Substitution Effect in an Iron Mixed Valence Complex

    N. Shida, Y. Suzawa, A. Okazawa, N. Kojima, M. Enomoto

    The 15th International Conference on Molecule-based Magnets (ICMM2016)  (Sendai International Center (Sendai, Japan)) 

    Presentation date: 2016.09

  • The ChargeTransfer Phase Transition In An Iron-Mixed Valence Complex With Specific π-Conjugated Cations As Intercalants

    M. Enomoto, M. Shirakawa, H. Izawa, K. Sato, A. Okazawa, N. Kojima

    The 15th International Conference on Molecule-based Magnets (ICMM2016)  (Sendai International Center (Sendai, Japan)) 

    Presentation date: 2016.09

  • Syntheses, Crystal Structures, and Magnetic Properties of Copper(II) Complexes with Bischelate and High-Spin Biradical Ligand

    A. Okazawa, T. Ishida, K. Ogawa, N. Kojima

    The 15th International Conference on Molecule-based Magnets (ICMM2016)  (Sendai International Center (Sendai, Japan)) 

    Presentation date: 2016.09

  • [Dy2Ni]型錯体における単分子磁石挙動とスピンエネルギーダイアグラム

    岡澤 厚, 野尻 浩之, 石田 尚行, 小島 憲道

    日本化学会第96春季年会 

    Presentation date: 2016.03

  • Magnetic Properties of V-Substitution Effect in an Iron Mixed Valence Complex

    SHIDA, Norihiro, SUZAWA, Yoshiki, INABA, Michikazu, OKAZAWA, Atsushi, KOJIMA, Norimichi, ENOMOTO, Masaya

    日本化学会第96春季年会 

    Presentation date: 2016.03

  • デカメチルメタロセニウムを挿入した鉄混合原子価錯体の合成と物性評価

    大橋 奈実, 井田 博道, 岡澤 厚, 小島 憲道, 榎本 真哉

    日本化学会第96春季年会 

    Presentation date: 2016.03

  • Pressure dependence of a ferromagnetic transition for cobalt layered hydroxides with diarylethene derivatives

    Yu Inada, Atsushi Okazawa, Norimichi Kojima, Masaya Enomoto

    日本化学会第96春季年会 

    Presentation date: 2016.03

  • 鉄置換ニオブ酸リチウム系強誘電体薄膜の可視光起電力評価

    高橋秀輔, 井上亮太郎, 松尾拓紀, 岡澤厚, 小島憲道, 石垣徹, 吉田幸彦, 野口祐二, 宮山勝

    第54回セラミックス基礎科学討論会 

    Presentation date: 2016.01

  • Proton-responsive emission properties in cyclometalated iridium(III) complex film, [IrIII(bdp)3]@Nafion (bdp = 2,4’-(benzene-1,3-diyl)dipyridine)

    Hajime Kamebuchi, Yu Fujimura, Atsushi Okazawa, Makoto Tadokoro, Norimichi Kojima

    The International Chemical Congress of Pacific Basin Societies 2015 (Pacifichem2015) 

    Presentation date: 2015.12

  • Effect on the ferromagnetic transition temperature of the cobalt layered hydroxides by employment of the monovalent diarylethene derivative with a carboxyl group

    Yu Inada, Shoko Kubota, Atsushi Okazawa, Norimichi Kojima, Masaya Enomoto

    The International Chemical Congress of Pacific Basin Societies 2015 (Pacifichem2015) 

    Presentation date: 2015.12

  • Syntheses and magnetic properties of transition-metal complexes with multichelating and high-spin radical ligands

    Atsushi Okazawa, Takayuki Ishida, Norimichi Kojima, Keiichiro Ogawa

    The International Chemical Congress of Pacific Basin Societies 2015 (Pacifichem2015) 

    Presentation date: 2015.12

  • Correlation between charge transfer on a magnetic layer of the iron mixed valence complex and molecular polarization of cationic intecalants

    Kazuma Arai, Hiromichi Ida, Atsushi Okazawa, Norimichi Kojima, Masaya Enomoto

    The International Chemical Congress of Pacific Basin Societies 2015 (Pacifichem2015) 

    Presentation date: 2015.12

  • Development of dilute magnetic materials - magnetic property and Mossbauer spectra of SrSnO3 doped with Fe and Sb

    Shigeyo Suzuki, Yuya Koike, Kiyoshi Nomura, Atsushi Okazawa, Norimichi Kojima

    The International Chemical Congress of Pacific Basin Societies 2015 (Pacifichem2015) 

    Presentation date: 2015.12

  • ジヒドロビピリジニウムと鉄錯体からなる電荷移動塩の酸蒸気によるベイポクロミズム

    田中 李叶子, 岡澤 厚, 小島 憲道, 松下 信之

    第24回有機結晶シンポジウム 

    Presentation date: 2015.11

  • 鉄置換ニオブ酸リチウム系強誘電体薄膜の光起電力特性

    高橋秀輔, 井上亮太郎, 松尾拓, 岡澤 厚, 小島憲道, 石垣 徹, 吉田幸彦, 野口祐二, 宮山 勝

    第 35 回エレクトロセラミックス研究討論会 

    Presentation date: 2015.10

  • 環状ジカチオンを挿入した鉄混合原子価錯体における磁性層の歪みと電荷移動挙動の変化

    須澤 嘉紀, 佐々木 翔太郎, 井田 博道, 榎本 真哉, 嶋田 紅葉, 横田 香織, 秋田 素子, 岡澤 厚, 小島 憲道

    錯体化学会第65回討論会 

    Presentation date: 2015.09

  • モノカルボン酸型ジアリールエテン誘導体を挿入したコバルト層状磁性体の磁気挙動変化

    稲田 雄, 久保田 尚子, 岡澤 厚, 小島 憲道, 榎本 真哉

    錯体化学会第65回討論会 

    Presentation date: 2015.09

  • 直線型二配位構造を有する有機鉄錯体の合成と物性

    松尾 司, 合田 舜, 伊藤幹直, 橋爪大輔, 玉尾皓平, 岡澤 厚, 小島憲道, 小林義男, 笛野博之, 田中一義

    第62回有機金属化学討論会 

    Presentation date: 2015.09

  • 陽イオン交換膜Nafionに担持されたシクロメタレート型イリジウム(III)錯体のpHに依存した発光特性

    藤村 有生, 亀渕 萌, 岡澤 厚, 小島 憲道

    日本化学会第95春季年会 

    Presentation date: 2015.03

  • かさ高いRind基を有する有機鉄二価錯体の還元反応

    合田 舜, 岡澤 厚, 小島 憲道, 橋爪 大輔, 小林 義男, 田中 一義, 笛野 博之, 松尾 司

    日本化学会第95春季年会 

    Presentation date: 2015.03

  • 基底高スピンかつマルチなキレート部位を有するビラジカル配位子およびその遷移金属錯体の合成と磁性

    岡澤 厚, 小島 憲道

    日本化学会第95春季年会 

    Presentation date: 2015.03

  • ヘキサシアニド鉄(II)錯体電荷移動塩の酸蒸気による二段階ベイポクロミズムにおける橙色相の解明

    田中 李叶子, 岡澤 厚, 小島 憲道, 松下 信之

    日本化学会第95春季年会 

    Presentation date: 2015.03

  • アニオン部位の異なるジアリールエテン誘導体を挿入したコバルト層状磁性体の磁気挙動変化

    稲田 雄, 久保田 尚子, 岡澤 厚, 小島 憲道, 榎本 真哉

    錯体化学会第64回討論会 

    Presentation date: 2014.09

  • モノチオシュウ酸架橋層状ヘテロ金属錯体のスピン平衡に対する金属置換効果

    深尾 陽一, 影澤 幸一, 岡澤 厚, 小島 憲道, 榎本 真哉

    錯体化学会第64回討論会 

    Presentation date: 2014.09

  • 2価カチオンのアルキル鎖長がもたらす層状鉄混合原子価錯体における電荷移動挙動の変化

    佐々木 翔太郎, 井田 博道, 榎本 真哉, 岡澤 厚, 小島 憲道

    錯体化学会第64回討論会 

    Presentation date: 2014.09

  • ジアリールエテン誘導体を挿入したコバルト層状水酸化物における層間π共役系の磁性への寄与

    久保田 尚子, 大島 祐史, 榎本 真哉, 岡澤 厚, 小島 憲道

    錯体化学会第64回討論会 

    Presentation date: 2014.09

  • pH応答発光性イリジウム(III)錯体膜の開発

    亀渕 萌, 岡澤 厚, 小島 憲道

    錯体化学会第64回討論会 

    Presentation date: 2014.09

  • 直線型二配位構造を有する有機鉄二核錯体の合成と物性

    合田 舜, 岡澤 厚, 小島 憲道, 橋爪 大輔, 小林 義男, 田中 一義, 笛野 博之, 松尾 司

    錯体化学会第64回討論会 

    Presentation date: 2014.09

  • The distortional effect on the magnetic layer of the iron mixed valence complex due to introduction of divalent cationic intercalants

    Shotaro Sasaki, Hiromichi Ida, Atsushi Okazawa, Norimichi Kojima, Masaya Enomoto

    The 14th International Conference on Molecule-Based Magnets (ICMM2014) 

    Presentation date: 2014.07

  • Control of ferromagnetic transition temperature in a cobalt layered magnet with a carboxylated diarylethene derivative as an intercalant

    Yu Inada, Shoko Kubota, Atsushi Okazawa, Norimichi Kojima, Masaya Enomoto

    The 14th International Conference on Molecule-Based Magnets (ICMM2014) 

    Presentation date: 2014.07

  • Study on the Static and Dynamic Spin-crossover Phenomena in Tripyrazolylmethane Iron(II) Complexes by Muon Spectroscopy

    H. Kobayashi, A. Okazawa, I. Kawasaki, I. Watanabe, N. Kojima

    The 14th International Conference on Molecule-Based Magnets (ICMM2014) 

    Presentation date: 2014.07

  • Magnetic Switching by Photo-irradiation in the Spin-crossover Iron(III) Complex with Photoisomerizable Counteranion

    H. Kamebuchi, A. Sugahara, A. Okazawa, N. Kojima

    The 14th International Conference on Molecule-Based Magnets (ICMM2014) 

    Presentation date: 2014.07

  • 4f-3dヘテロスピン系錯体における単分子磁石性能および交換相互作用の化学的傾向

    岡澤 厚, 吉居 俊輔, 野尻 浩之, 石田 尚行, 小島 憲道  [Invited]

    第1回東北大学リーディング大学院研究会 

    Presentation date: 2014.04

  • シュウ酸およびジチオシュウ酸に架橋された新奇二核鉄錯体の合成と物性

    坂口 岳志, 井田 博道, 岡澤 厚, 小島 憲道, 榎本 真哉

    日本化学会第94春季年会 

    Presentation date: 2014.03

  • モノチオオキサレート架橋ヘテロ金属錯体におけるスピン平衡と電荷移動相転移

    深尾 陽一, 影澤 幸一, 岡澤 厚, 小島 憲道, 榎本 真哉

    日本化学会第94春季年会 

    Presentation date: 2014.03

  • カルボン酸部位を有するジアリールエテン誘導体を挿入したコバルト層状磁性体のπ共役系スイッチを利用した強磁性転移温度の制御

    稲田 雄, 久保田 尚子, 岡澤 厚, 小島 憲道, 榎本 真哉

    日本化学会第94春季年会 

    Presentation date: 2014.03

  • pHに依存した発光特性を示すRu(II)錯体膜の開発と発光挙動の制御

    玉樹 怜, 亀渕 萌, 岡澤 厚, 小島 憲道

    日本化学会第94春季年会 

    Presentation date: 2014.03

  • 直線型二配位構造を有する有機鉄二価二核錯体の合成と物性

    合田 舜, 岡澤 厚, 小島 憲道, 橋爪 大輔, 小林 義男, 笛野 博之, 田中 一義, 松尾 司

    日本化学会第94春季年会 

    Presentation date: 2014.03

  • 鉄(II)スピンクロスオーバー錯体における動的スピン平衡のμSR法による研究

    小林 弘明, 岡澤 厚, 小島 憲道, 川崎 郁斗, 渡邊 功雄

    日本化学会第94春季年会 

    Presentation date: 2014.03

  • アニオン性スピロピランを挿入したコバルト層状水酸化物の開発とその光磁性

    田中 成, 岡澤 厚, 小島 憲道

    日本化学会第94春季年会 

    Presentation date: 2014.03

  • メスバウアー分光とミュオン分光からみた動的および静的スピンクロスオーバー鉄(II)錯体におけるスピンダイナミクス

    岡澤 厚, 小林弘明, 小島憲道, 川崎郁斗, 渡邊功雄

    第16回メスバウアー分光研究会シンポジウム 

    Presentation date: 2014.03

  • メスバウアー分光を用いたシアノ架橋錯体の電極反応の解析

    大久保 將史, 西村 真一, 山田 淳夫, 水野 善文, 朝倉 大輔, 岡澤 厚, 小島 憲道

    第15回メスバウアー分光研究会シンポジウム 

    Presentation date: 2014.03

  • 光異性化分子を対アニオンに導入したスピンクロスオーバー鉄錯体の磁気特性

    菅原 哲, 亀渕 萌, 岡澤 厚, 小島 憲道

    第15回メスバウアー分光研究会シンポジウム 

    Presentation date: 2014.03

  • スピン平衡を示すスピンクロスオーバー鉄(II)錯体におけるメスバウアー分光とミュオン分光からみた動的挙動

    小林 弘明, 岡澤 厚, 小島 憲道, 川崎 郁斗, 渡邊 功雄

    第15回メスバウアー分光研究会シンポジウム 

    Presentation date: 2014.03

  • スピン平衡を示す鉄(II)錯体のメスバウアー分光およびミュオン分光からみた動的挙動

    小林 弘明, 岡澤 厚, 川崎 郁斗, 渡邊 功雄, 小島 憲道

    平成25年度KUR専門研究会「不安定原子核の理工学と物性応用研究III」 

    Presentation date: 2013.12

  • Development of the proton responsive spin-crossover complex film and its electrical control of the spin state accompanied by proton conduction

    H. Kamebuchi, T. Jo, A. Okazawa, N. Kojima

    4th Asian Conference on Coordination Chemistry (ACCC4) 

    Presentation date: 2013.11

  • [Dy2M]型4f-3dヘテロスピン錯体における単分子磁石挙動の化学修飾

    岡澤 厚, 石田 尚行, 野尻 浩之, 小島 憲道

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • 鉄混合原子化錯体の特異な電荷移動挙動に対するコバルト置換効果

    豊田 靖央, 井田 博道, 稲葉 道一, 岡澤 厚, 小島 憲道, 榎本 真哉

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • 層間相互作用スイッチとしての光異性化分子を挿入した銅層状水酸化物の磁気挙動制御

    川上 日向子, 久保田 尚子, 田中 美幸, 大島 祐史, 岡澤 厚, 小島 憲道, 榎本 真哉

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • 光異性化配位子を含む金属錯体を挿入したコバルト層状磁性体の開発

    稲田 雄, 久保田 尚子, 岡澤 厚, 小島 憲道, 榎本 真哉

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • アニオン性スピロピランを挿入したコバルト層状水酸化物の合成とその光磁性

    田中 成, 菅原 哲, 岡澤 厚, 小島 憲道

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • 分子分極を持つローター分子を挿入した鉄混合原子価錯体における電荷移動挙動の変化

    新井 一馬, 井田 博道, 岡澤 厚, 榎本 真哉, 小島 憲道

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • 層間分子がもたらす鉄混合原子価錯体における磁性層の歪みによる電荷移動挙動の変化

    佐々木 翔太郎, 井田 博道, 岡澤 厚, 小島 憲道, 榎本 真哉

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • コバルト層状磁性体における光異性化分子のπ電子系スイッチを利用した強磁性転移温度の制御

    久保田 尚子, 大島 祐史, 岡澤 厚, 小島 憲道, 榎本 真哉

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • ジチオオキサレート架橋Fe二核ユニットにおける分子間相互作用を介したスピンクロスオーバー挙動の変化

    山科 駿, 坂口 岳志, 井田 博道, 小島 憲道, 岡澤 厚, 榎本 真哉

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • かさ高いアリール基を有する有機鉄二価錯体の合成と物性

    合田 舜, 松尾 司, 伊藤 幹直, 橋爪 大輔, 玉尾 皓平, 岡澤 厚, 小島 憲道, 小林 義男

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • スピンクロスオーバー錯体における動的スピン平衡のミューオンスピン分光による研究

    小林 弘明, 岡澤 厚, 小島 憲道, 川崎 郁斗, 渡邊 功雄

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • 光異性化分子を対アニオンとしたスピンクロスオーバー鉄(III)錯体[FeIII(qsal)2]SP (SP = spiropyran)の光照射による磁性変換

    亀渕 萌, 菅原 哲, 岡澤 厚, 小島 憲道

    錯体化学会第63回討論会 

    Presentation date: 2013.11

  • Study on spin configurations in photoresponsive iron mixed-valence complexes by Mossbauer spectroscopy

    A. Okazawa, J. Yoshida, N. Kida, I. Kashima, W. Murata, M. Enomoto, N. Kojima

    International Conference on the Applications of the Mossbauer Effect 2013 (ICAME2013) 

    Presentation date: 2013.09

  • Study on concerted phenomena coupled with rapid spin-equilibrium and magnetic phase transition for (C6H5)4P[MnIIFeIII(C2O3S)3] by 57Fe Mossbauer spectroscopy

    N. Kojima, K. Kagesawa, A. Okazawa, M. Enomoto

    International Conference on the Applications of the Mossbauer Effect 2013 (ICAME2013) 

    Presentation date: 2013.09

  • Magnetostructural correlation for 1D spin-crossover system, [FeII(NH2-triazole)3(CnH2n+1SO3)2-xH2O

    H. Kamebuchi, A. Nakamoto, M. Enomoto, T. Yokoyama, N. Kojima

    International Conference on the Applications of the Mossbauer Effect 2013 (ICAME2013) 

    Presentation date: 2013.09

  • プルシアンブルー類似体におけるマグネシウムイオン挿入・脱離反応の解析

    水野善文, 大久保將史, 朝倉大輔, 影澤幸一, 岡澤 厚, 小島憲道, 大石克嘉, 工藤徹一, 周 豪慎

    第53回電池討論会 

    Presentation date: 2012.11

  • Topotactic Solid State Redox of a Cyano-bridged Magnet

    M. Okubo, K. Kagesawa, Y. Mizuno, D. Asakura, H. S. Zhou, A. Okazawa, N. Kojima

    The 13th International Conference on Molecule-based Magnets (ICMM2012) 

    Presentation date: 2012.10

  • Cation Size Effect on Photomagnetism and Charge Transfer Phase Transition of Iron Mixedvalence Complexes with Spiropyrans

    J. Yoshida, N. Kida, A. Okazawa, N. Kojima

    The 13th International Conference on Molecule-based Magnets (ICMM2012) 

    Presentation date: 2012.10

  • Precise Electrochemical Control of Ferromagnetism in a Bimetallic NiFe Prussian Blue Analog

    Y. Mizuno, M. Okubo, K. Kagesawa, D. Asakura, T. Kudo, H. Zhou, K. Oh-ishi, A. Okazawa, N. Kojima

    The 13th International Conference on Molecule-based Magnets (ICMM2012) 

    Presentation date: 2012.10

  • Electric-Field Manipulation of the Spin State in Transparent pH-Sensitive Spin-Crossover Complex, [FeII(diAMsar)]@Nafion

    H. Kamebuchi, T. Jo, A. Okazawa, M. Enomoto, N. Kojima

    The 13th International Conference on Molecule-based Magnets (ICMM2012) 

    Presentation date: 2012.10

  • Chemical Modification of 4f-3d Heterometallic [Ln2Ni]-type Single-Molecule Magnets

    A. Okazawa, T. Ishida, H. Nojiri, S. Yoshii, N. Kojima

    The 13th International Conference on Molecule-based Magnets (ICMM2012) 

    Presentation date: 2012.10

  • レドックス活性白金錯体の磁性

    吉田 真那, 岡澤 厚, 渡邉 永治, 小島 憲道, 松下 信之

    錯体化学会第62回討論会 

    Presentation date: 2012.09

  • 特異な環状π電子系分子およびその前駆体を挿入した鉄混合原子価錯体における電荷移動挙動の制御

    白川 雅彦, 井田 博道, 榎本 真哉, 岡澤 厚, 小島 憲道, 佐藤 潔

    錯体化学会第62回討論会 

    Presentation date: 2012.09

  • シュウ酸およびジチオシュウ酸に架橋された新奇二核鉄錯体の合成と物性

    井田 博道, 岡澤 厚, 小島 憲道, 榎本 真哉

    錯体化学会第62回討論会 

    Presentation date: 2012.09

  • アニオン性スピロピランを対イオンとするトリアゾール架橋鉄(II)錯体の合成とスピンクロスオーバー挙動

    田中 成, 菅原 哲, 岡澤 厚, 小島 憲道

    錯体化学会第62回討論会 

    Presentation date: 2012.09

  • ピリジンやピリミジンを含む新規ニトロキシドキレート錯体の合成と性質

    本間 雄太, 岡澤 厚, 石田 尚行

    第6回分子科学討論会 

    Presentation date: 2012.09

  • シアノ架橋配位高分子における固体電気化学反応による磁性制御

    大久保 將史, 影澤 幸一, 水野 善文, 朝倉 大輔, 細野 英司, 工藤 徹一, 周 豪慎, 岡澤 厚, 小島 憲道

    錯体化学会第61回討論会 

    Presentation date: 2012.09

  • モノチオオキサラト架橋鉄混合原子価錯体におけるスピン平衡と原子価揺動

    吉田 順哉, 影澤 幸一, 岡澤 厚, 榎本 真哉, 小島 憲道

    錯体化学会第61回討論会 

    Presentation date: 2012.09

  • pH応答スピンクロスオーバー錯体膜の開発と電場によるスピン状態の時空間制御

    亀渕 萌, 城 健智, 岡澤 厚, 榎本 真哉, 清水 秀治, 小島 憲道

    第6回分子科学討論会 

    Presentation date: 2012.09

  • 単分子磁石を目指したニトロキシドラジカル-ランタノイド錯体の磁性の解明

    村上 里奈, 岡澤 厚, 吉居 俊輔, Michael L. Baker, 野尻 浩之, 石田 尚行

    第6回分子科学討論会 

    Presentation date: 2012.09

  • Ferro- and Antiferromagnetic Couplings of (MV)Cu2Cl6 (MV = methylviologen)

    Y. Seki, A. Okazawa, M. Enomoto, J. Harada, K. Ogawa, N. Kojima

    XXIst International Symposium on the Jahn-Teller Effect (JT2012) 

    Presentation date: 2012.08

  • ランタノイド−ニトロキシドラジカル錯体系の単分子磁石の探索

    村上 里奈, 岡澤 厚, 吉居 俊輔, 野尻 浩之, 石田 尚行

    日本化学会第92春季年会 

    Presentation date: 2012.03

  • 4f-3d錯体における交換相互作用と磁気異方性

    島田 貴士, 岡澤 厚, 吉居 俊輔, 野尻 浩之, 石田 尚行

    日本化学会第92春季年会 

    Presentation date: 2012.03

  • 電荷移動錯体β’’-[BEDT-TTF]4[ReCl4(oxalate)](C6H5CN)の結晶構造と伝導性

    霜鳥 文俊, 榎本 真哉, 岡澤 厚, 小島 憲道

    日本化学会第92春季年会 

    Presentation date: 2012.03

  • 基底三重項ピリミジン-4,6-ジイルビス(tert-ブチルニトロキシド)の合成と性質

    本間 雄太, 岡澤 厚, 石田 尚行

    日本化学会第92春季年会 

    Presentation date: 2012.03

  • 直線二配位Fe錯体の巨大内部磁場(2)

    小林 義男, 伊藤 幹直, 松尾 司, 森 雅樹, 中村 仁, 岡澤 厚, 小島 憲道, 玉尾 皓平

    日本化学会第92春季年会 

    Presentation date: 2012.03

  • 鉄混合原子価錯体[FeIIFeIII(C2O2S2)3]におけるマンガンによる磁性イオン置換効果

    井田 博道, 榎本 真哉, 岡澤 厚, 小島 憲道

    日本化学会第92春季年会 

    Presentation date: 2012.03

  • アニオン性スピロピランを対イオンに用いたスピンクロスオーバー鉄錯体の磁性

    菅原 哲, 田中 成, 岡澤 厚, 小島 憲道

    日本化学会第92春季年会 

    Presentation date: 2012.03

  • モノチオオキサレート架橋鉄錯体における動的スピンクロスオーバー現象の圧力効果

    松岡 貴文, 影澤 幸一, 岡澤 厚, 小島 憲道

    日本化学会第92春季年会 

    Presentation date: 2012.03

  • 光応答性鉄混合原子価錯体(SP-R)[FeIIFeIII(dto)3](SP = spiropyran; R = alkyl group; dto = C2O2S2)における磁気特性の対カチオンサイズ効果の研究

    吉田 順哉, 岡澤 厚, 小島 憲道

    日本化学会第92春季年会 

    Presentation date: 2012.03

  • 2種類のジアリールエテン誘導体を挿入したコバルト層状水酸化物における光誘起多段階磁気制御

    大島 裕史, 榎本 真哉, 岡澤 厚, 小島 憲道

    日本化学会第92春季年会 

    Presentation date: 2012.03

  • ベルダジルラジカルが配位した新奇鉄(II)錯体[FeII(vdco)2(H2O)2]2H2Oの結晶構造と物性:水分子の配向挙動に起因する57Feメスバウアースペクトルの異常な振舞いの解明

    亀渕 萌, 岡澤 厚, 榎本 真哉, 原田 潤, 小川 桂一郎, 大久保 将史, Train, Cyrille・Verdaguer, Michel, 丸田 悟朗, 武田 定, 小島 憲道

    日本化学会第92春季年会 

    Presentation date: 2012.03

  • 57Feメスバウアー分光法を用いた集積型混合原子価鉄錯体の強磁性相および原子価揺動の研究

    岡澤厚, 小島憲道

    メスバウアー分光研究会 

    Presentation date: 2012.03

  • 直線型二配位鉄錯体のメスバウアー分光研究(III)

    小林義男, 松尾 司, 伊藤幹直, 長友 傑, 中村 仁, 森 雅樹, 岡澤 厚, 小島憲道, 玉尾皓平

    京都大学原子炉実験所専門研究会「不安定原子核の理工学と物性応用研究」 

    Presentation date: 2011.12

  • t-ブチル2-ピリジルニトロキシド-ランタノイド(Ln = Gd, Tb, Dy)錯体における比較的強い反強磁性的相互作用

    村上里奈, 岡澤厚, 吉居俊輔, 野尻浩之, 石田尚行

    第50回電子スピンサイエンス学会年会 

    Presentation date: 2011.11

  • ピリミジン-4,6-ジイルビス(tert-ブチルニトロキシド)の合成及び性質

    本間雄太, 岡澤厚, 石田尚行

    第50回電子スピンサイエンス学会年会 

    Presentation date: 2011.11

  • Study on the Ferromagnetic State in Iron Mixed-Valence Complexes A[FeIIFeIII(dto)3] (A = (n-CnH2n+1)4N, Spiropyrna; dto = C2O2S2) by Means of Mossbauer Spectroscopy

    Y. Ono, A. Okazawa, N. Kida, J. Yoshida, M. Enomoto, N. Kojima

    31th International Conference on the Applications of the M?ssbauer Effect (ICAME2011) 

    Presentation date: 2011.09

  • 5配位ゲルマニウム配位子を有する鉄ジカルボニル錯体の合成と構造

    狩野 直和, 吉成 直人, 川島 隆幸, 榎本 真哉, 岡澤 厚, 小島 憲道

    第60回錯体化学討論会 

    Presentation date: 2011.09

  • アルカリ金属イオンによるプルシアンブルー類似体における磁気特性の制御

    水野 善文, 大久保 將史, 朝倉 大輔, 大石 克嘉, 工藤 徹一, 周 豪慎, 岡澤 厚, 小島 憲道

    第5回分子科学討論会 

    Presentation date: 2011.09

  • ラジカル二座配位子を目指したピリミジン-4,6-ジイルビス(tert-ブチルニトロキシド)の合成

    本間 雄太, 岡澤 厚, 石田 尚行

    第22回基礎有機化学討論会 

    Presentation date: 2011.09

  • 無欠陥型プルシアンブルー類似体のリチウムイオン二次電池用電極特性へのFe置換効果

    水野 善文, 大久保 將史, 朝倉 大輔, 大石 克嘉, 工藤 徹一, 周 豪慎, 岡澤 厚, 小島 憲道

    錯体化学会第61回討論会 

    Presentation date: 2011.09

  • プルシアンブルー類似体におけるイオンによる可逆的磁性スイッチング

    大久保 將史, 水野 善文, 朝倉 大輔, 工藤 徹一, 周 豪慎, 池戸 一道, 溝川 貴司, 本間 格, 岡澤 厚, 小島 憲道

    錯体化学会第61回討論会 

    Presentation date: 2011.09

  • 直線三核 Cu-Ln-Cu 金属錯体における交換相互作用のランタノイドイオン依存性

    島田 貴士, 藤原 慶, 岡澤 厚, 田中 豪, 吉居 俊輔, 野尻 浩之, 石田 尚行

    錯体化学会第61回討論会 

    Presentation date: 2011.09

  • 4f-3d系錯体におけるランタノイド-ニッケルイオン間に働く交換相互作用の決定

    岡澤 厚, 石田 尚行, 吉居 俊輔, 野尻 浩之, 小島 憲道

    錯体化学会第61回討論会 

    Presentation date: 2011.09

  • アルカリ金属イオンによるプルシアンブルー類似体における磁気制御

    水野 善文, 大久保 將史, 朝倉 大輔, 大石 克嘉, 工藤 徹一, 周 豪慎, 岡澤 厚, 小島 憲道

    錯体化学会第61回討論会 

    Presentation date: 2011.09

  • モノチオオキサレート架橋集積型ヘテロ金属錯体におけるスピン平衡と磁気特性

    影澤 幸一, 岡澤 厚, 小島 憲道

    錯体化学会第61回討論会 

    Presentation date: 2011.09

  • モノチオオキサレート架橋鉄錯体におけるスピンクロスオーバー現象のカチオンサイズ効果

    松岡 貴文, 影澤 幸一, 岡澤 厚, 小島 憲道

    錯体化学会第61回討論会 

    Presentation date: 2011.09

  • 光異性化分子を対イオンに用いたスピンクロスオーバー鉄(III)錯体の構造と磁性

    菅原 哲, 岡澤 厚, 原田 潤, 小川 桂一郎, 小島 憲道

    錯体化学会第61回討論会 

    Presentation date: 2011.09

  • pH依存スピンクロスオーバー錯体膜における動的スピン転移挙動

    亀渕 萌, 城 健智, 清水 秀治, 岡澤 厚, 榎本 真哉, 小島 憲道

    錯体化学会第61回討論会 

    Presentation date: 2011.09

  • Synthesis and Structures of Anionic Iron Complexes bearing a Pentacoordinated Silicon or Germanium Atom

    N. Kano, N. Yoshinari, T. Kawashima, M. Enomoto, A. Okazawa, N. Kojima, J.-D. Guo, S. Nagase

    16th International Symposium on Silicon Chemistry (ISOS XVI) 

    Presentation date: 2011.08

  • 4f-3d金属三核錯体における交換相互作用のランタノイドイオン依存性

    島田 貴士, 藤原 慶, 岡澤 厚, 田中 豪, 吉居 俊輔, 野尻 浩之, 石田 尚行

    日本化学会第91春季年会 

    Presentation date: 2011.03

  • (n-CnH2n+1)4N[ZnIIFeIII(C2O3S)3](n = 2-4)におけるカチオンサイズ効果を用いたスピン平衡の制御

    影澤 幸一, 岡澤 厚, 小島 憲道

    日本化学会第91春季年会 

    Presentation date: 2011.03

  • 光異性化分子ジアリールエテンをインターカレートした有機無機ハイブリッドシステムの構築

    小林 克彦, 岡澤 厚, 小島 憲道

    日本化学会第91春季年会 

    Presentation date: 2011.03

  • ジアセチレンをインターカレートした磁性有機・無機ハイブリッドシステムの構築

    石田 拓也, 岡澤 厚, 小島 憲道

    日本化学会第91春季年会 

    Presentation date: 2011.03

  • スピン転移類似挙動を示すπ-d へテロスピン系」、新学術領域研究「分子自由度が拓く新物質科学

    石田尚行, 岡澤 厚

    新学術領域研究「分子自由度が拓く新物質科学」第4回領域会議 

    Presentation date: 2011.01

  • Study on the spin equilibrium and magnetic ordering in Ph4P[MnIIFeIII(mto)3] (Ph = C6H5, mto = C2O3S)

    K. Kagesawa, A. Okazawa, M. Enomoto, N. Kojima

    2010 International Chemical Congress of Pacific Basin Societies (Pacifichem 2010) 

    Presentation date: 2010.12

  • Spin-transition-like behavior of radical chelate complexes accompanied by twisted deformation around a copper(II)-nitroxide coordination bond

    A. Okazawa, T. Ishida, N. Kojima

    2010 International Chemical Congress of Pacific Basin Societies (Pacifichem 2010) 

    Presentation date: 2010.12

  • Study on the magnetism and anomalous behavior of 57Fe Mossbauer spectra for iron(II) complex coordinated by verdazyl radical

    H. Kamebuchi, A. Okazawa, M. Enomoto, J. Harada, K. Ogawa, M. Okubo, C. Train, M. Verdaguer, N. Kojima

    2010 International Chemical Congress of Pacific Basin Societies (Pacifichem 2010) 

    Presentation date: 2010.12

  • Determination of exchange couplings in dinuclear 4f-3d heterometallic nanosized magnets

    T. Ishida, R. Watanabe, K. Fujiwara, A. Okazawa, G. Tanaka, S. Yoshii, H. Nojiri

    2010 International Chemical Congress of Pacific Basin Societies (Pacifichem 2010) 

    Presentation date: 2010.12

  • Control of Magnetic Properties and Electronic Structures in Prussian Blue Analogues by Electrochemical Ion Extraction

    M. Okubo, D. Asakura, T. Kudo, H. Zhou, K. Ikedo, T. mizokawa, A. Okazawa, N. Kojima

    60th Annversary Conference on Coordination Chemistry in OSAKA, Japan (60CCCO) 

    Presentation date: 2010.09

  • 光応答性有機分子をインターカレートした層状ペロブスカイト型銅錯体の構築と物性

    関 泰史, 岡澤 厚, 原田 潤, 小川 桂一郎, 小島 憲道

    第60回錯体化学討論会 

    Presentation date: 2010.09

  • かご型配位子を有する新規スピンクロスオーバー錯体膜の開発とそのpH依存性

    亀渕 萌, 城 健智, 岡澤 厚, 榎本 真哉, 小島 憲道

    第60回錯体化学討論会 

    Presentation date: 2010.09

  • 集積型金属錯体[M(II)Fe(III)(mto)3] (mto = C2O3S)における速いスピン平衡と磁気特性

    影澤 幸一, 岡澤 厚, 小島 憲道

    第60回錯体化学討論会 

    Presentation date: 2010.09

  • Kイオン脱離過程におけるプルシアンブルー類似体の磁気状態変化

    朝倉大輔, 大久保將史, 工藤徹一, 周豪慎, 溝川貴司, 岡澤厚, 小島憲道

    日本物理学会2010年秋季大会 

    Presentation date: 2010.09

  • ランタノイドイオンと銅イオンを組み合せた単分子磁石における交換相互作用の解明

    藤原 慶, 渡邉 亮, 岡澤 厚, 田中 豪, 吉居 俊輔, 野尻 浩之, 石田 尚行

    第4回分子科学討論会 

    Presentation date: 2010.09

  • プルシアンブルー類似体のKイオン脱離過程における電子状態・磁性変化

    大久保 將史, 朝倉 大輔, 工藤 徹一, 周 豪慎, 池戸 一道, 溝川 貴司, 岡澤 厚, 小島 憲道

    第4回分子科学討論会 

    Presentation date: 2010.09

  • 速いスピン平衡を有する集積型金属錯体[MnII FeIII(mto)3](mto = C2O3S)における特異な磁気相転移

    影澤 幸一, 岡澤 厚, 小島 憲道

    第4回分子科学討論会 

    Presentation date: 2010.09

  • 光酸化還元機能を有するビオロゲンを対カチオンとする一次元白金錯体の合成・構造・物性

    関 泰史, 岡澤 厚, 榎本 真哉, 原田 潤, 小川 桂一郎, 小島 憲道

    日本化学会第90春季年会 

    Presentation date: 2010.03

  • プロトン濃度による磁性制御を目ざしたスピンクロスオーバー錯体膜の開発

    城 健智, 榎本 真哉, 岡澤 厚, 小島 憲道

    日本化学会第90春季年会 

    Presentation date: 2010.03

  • ベルダジルラジカル―鉄(II)錯体の結晶水が配位子場に与える影響

    亀渕 萌, 岡澤 厚, 榎本 真哉, 原田 潤, 小川 桂一郎, 大久保 将史, Train, Cyrille・Verdaguer, Michel, 田所 誠, 小島 憲道

    日本化学会第90春季年会 

    Presentation date: 2010.03

  • [Fe(4-NH2trz)3](X)2(X = tos, abs)におけるカウンターアニオンの構造異性がスピンクロスオーバー挙動に及ぼす効果

    菅原 哲, 岡澤 厚, 榎本 真哉, 小島 憲道

    日本化学会第90春季年会 

    Presentation date: 2010.03

  • (C6H5)4P[MnIIFeIII(C2O3S)3]における速いスピン平衡と磁気秩序化に関する研究

    影澤 幸一, 岡澤 厚, 榎本 真哉, 小島 憲道

    日本化学会第90春季年会 

    Presentation date: 2010.03

  • サレン型配位子を用いてランタノドイオンと遷移金属イオンを組み合わせたヘテロスピン2核錯体の交換相互作用

    渡邉 亮, 藤原 慶, 岡澤 厚, 田中 豪, 吉居 俊輔, 野尻 浩之, 石田 尚行

    日本化学会第90春季年会 

    Presentation date: 2010.03

  • 鉄混合原子価錯体(CnH2n+1)4N[Fe(II)Fe(III)(mto)3](n = 3,4; mto = C2O3S)における速いスピン平衡と電荷揺動の協奏現象

    影澤幸一, 岡澤厚, 榎本真哉, 小島憲道

    京都大学原子炉実験所専門研究会「短寿命核および放射線を用いた物性研究(II)」 

    Presentation date: 2009.12

  • ランタニドイオンと遷移金属イオンを組み合せた新規な単分子磁石開発とその磁気構造の解明

    藤原 慶, 渡邉 亮, 岡澤 厚, 野尻浩之, 石田尚行

    東京農工大学・電気通信大学第六回合同シンポジウム「ナノ未来材料とコヒーレント光科学」 

    Presentation date: 2009.12

  • Ln(III)-V(IV)錯体の磁気構造の解明とLn(III)-Cu(II)錯体との比較

    渡邉 亮, 岡澤 厚, 藤原 慶, 野上 隆, 野尻浩之, 石田尚行

    第48回電子スピンサイエンス学会年会 

    Presentation date: 2009.11

  • RE-3dヘテロメタル分子磁石のESRによる評価

    野尻浩之, 林美咲, 田中豪, 吉居俊輔, A. Gomella, 石田尚行, 岡澤厚

    第48回電子スピンサイエンス学会年会 

    Presentation date: 2009.11

  • RE-3dヘテロ金属分子磁性体の交換相互作用と磁性

    野尻浩之, 林美咲, 田中豪, 吉居俊輔, 石田尚行, 岡澤厚

    日本物理学会2009年秋季大会 

    Presentation date: 2009.09

  • 遷移金属イオンを変えた[DyMDy]型三核錯体における単分子磁石性能の比較

    岡澤 厚, 野尻 浩之, 野上 隆, 石田 尚行

    第59回錯体化学討論会 

    Presentation date: 2009.09

  • [LnMLn]型錯体における4f-3dスピン間の交換相互作用

    岡澤 厚, 根津 将, 野尻 浩之, 石田 尚行

    第3回分子科学討論会 

    Presentation date: 2009.09

  • 4f-3dヘテロスピン系錯体におけるランタノイドイオン種と交換相互作用との相関

    岡澤 厚, 渡邉 亮, 野尻 浩之, 野上 隆, 石田 尚行

    日本化学会第89春季年会 

    Presentation date: 2009.03

  • サレン型コンパートメント配位子を利用したランタノイド(III)とバナジウム(IV)を組み合わせた錯体の研究

    渡邉 亮, 岡澤 厚, 野尻 浩之, 野上 隆, 石田 尚行

    日本化学会第89春季年会 

    Presentation date: 2009.03

  • 希土類イオンと遷移金属イオンを用いた単分子磁石を目指して

    渡邉 亮, 岡澤 厚, 野尻浩之, 野上 隆, 石田尚行

    東京農工大学・電気通信大学 21 世紀 COE プログラム、第五回合同シンポジウム「ナノ未来材料とコヒーレント光科学」 

    Presentation date: 2008.12

  • ビス(ヘテロアリール)ニトロキシドおよびそのキレート錯体の合成と磁性

    岡澤 厚, 永市泰規, 野上 隆, 石田尚行

    第19回基礎有機化学討論会(第38回構造有機化学討論会) 

    Presentation date: 2008.10

  • Magnetic properties and exchange couplings of one-dimentionally arrayed 4f-3d heterometallic [Ln2Cu2]n compounds

    A. Okazawa, R. Watanabe, H. Nojiri, T. Nogami, T. Ishida

    The 11th International Conference on Molecule-Based Magnets (ICMM2008) 

    Presentation date: 2008.09

  • Strong ferromagnetic exchange couplings in copper(II) and nickel(II) complexes chelated with tert-butyl 5-methoxyphenyl-2-pyridyl nitroxide. A magneto-structural relationship

    A. Okazawa, Y. Terakado, T. Nogami, T. Ishida

    The 11th International Conference on Molecule-Based Magnets (ICMM2008) 

    Presentation date: 2008.09

  • RE-3dヘテロ金属分子磁性体の交換相互作用と磁性

    野尻浩之, 吉居俊輔, 石田尚行, 岡澤厚

    日本物理学会2008年秋季大会 

    Presentation date: 2008.09

  • High-Field ESR on Molecular-Based Nano-Magnets --- Application to Polyhedron Clusters and RareEarth Compounds

    Y. Oshima, H. Nojiri, S. Yoshii, P. K?gerler, M. Luban, A. M?ller, J. Schnack, A. Okazawa, T. Ishida

    Asian-Pacific EPR/ESR Symposium (APES08) 

    Presentation date: 2008.07

  • 複素芳香族の2位に置換したラジカルを用いたキレート錯体の研究

    寺門 雄太郎, 岡澤 厚, 石田 尚行, 野上 隆

    日本化学会第88春季年会 

    Presentation date: 2008.03

  • 単結晶構造相転移に伴うラジカル−銅(II)イオン間強磁性的/反強磁性的相互作用の熱的スイッチ

    岡澤 厚, 橋爪 大輔, 野上 隆, 石田 尚行

    日本化学会第88春季年会 

    Presentation date: 2008.03

  • 直線三核型4f-3dヘテロ金属錯体単分子磁石における交換相互作用の決定

    石田 尚行, 岡澤 厚, 渡邊 亮, 野上 隆, 野尻 浩之

    日本化学会第88春季年会 

    Presentation date: 2008.03

  • Magnetic Properties and Exchange Couplings of One-Dimensionally Arrayed 4f−3d Heterometallic [Ln2Cu2]n Compounds

    The 11th International Conference on Molecule-based Magnets (ICMM2008) 

    Presentation date: 2008

  • Preparation, Structure, and Magnetic Properties of Chelating Compounds of 2-Pyridyl Nitroxide Derivatives

    A. Okazawa, K. Osanai, T. Shimada, T. Nogami, T. Ishida

    The 10th International Conference on Molecule-based Magnets (ICMM 2006) 

    Presentation date: 2006

  • Structures and Magnetic Properties of Dinuclear Spiro-complexes for Orthogonality of Magnetic Orbitals

    A. Okazawa, T. Ishida, T. Nogami

    The 9th International Conference on Molecule-based Magnets (ICMM 2004) 

    Presentation date: 2004

▼display all

Research Projects

  • 溶解度の化学に立脚した高エネルギー密度レドックスフロー電解液の開発

    日本学術振興会  科学研究費助成事業 基盤研究(C)

    Project Year :

    2023.04
    -
    2026.03
     

    岡澤 厚

  • 水系レドックスフロー電池用の高濃度鉄錯体電解液の開発

    公益財団法人 住友電工グループ社会貢献基金  住友電工グループ社会貢献基金 2023年度 学術・研究助成

    Project Year :

    2023.10
    -
    2025.03
     

  • 溶解度の化学と機械学習に基づく高エネルギー密度なレドックスフロー電池活物質の開発

    公益財団法人 岩谷直治記念財団  第49回岩谷科学技術研究助成

    Project Year :

    2023.04
    -
    2024.03
     

  • Development of Multisite Radical Chelate Ligands and Ferrimagnetic Materials

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Project Year :

    2018.04
    -
    2021.03
     

  • 低次元応力場によるギミックで創出するメカノマグネティック材料

    公益財団法人池谷科学技術振興財団  2020年度単年度研究助成

    Project Year :

    2020.04
    -
    2021.03
     

  • 低温化学溶液還元によって酸化物中の遷移金属元素の価数を制御する

    日本学術振興会  科学研究費助成事業 基盤研究(C)

    Project Year :

    2017.04
    -
    2020.03
     

    井上 亮太郎, 岡澤 厚

     View Summary

    平成29年度に、酸化物LiNbO3中にある遷移金属元素Feの価数を低温化学溶液還元によって制御することに成功した。これは当初の予定通りであった。その過程で予想していなかった実験結果を得て、その原因を考えることによって、還元の制御機構について新しい物理的モデルの確立に成功した。このため、研究計画を前倒しして平成30年度前半にこの物理的モデルについて論文を投稿する予定を立てたが、データ解析の定量性に問題が生じ、平成30年度内に論文を投稿できなかった。問題解決のめどはある程度たったので、平成31年度前半には投稿したいと考えている。
    論文執筆作業と並行して平成30年度後半では、低温化学溶液還元技術の更なる開発を行った。具体的にはLiNbO3に加えてBiFeO3やBaTiO3粉末を準備し、低温化学溶液還元によってドープしたFeやMnなどの遷移金属元素の価数制御を試みた。どの粉末においても還元には成功したが、まだ系統的な実験結果を得るに至っていない。M&ouml;ssbauer分光測定に必要なCo線源の強度が研究開始当初の予想よりも落ちてきているため、今後はESR(電子スピン共鳴)測定なども併用して遷移金属元素の価数決定を行うことを考えている。
    平成31年度からは、還元機構のさらなる解明に向けて、遷移金属二元酸化物の還元をも試みる。合わせて酸化物強誘電体の光電変換機能増強や酸化物高温超伝導体の超伝導転移温度制御などのデモンストレーションを行い、研究をまとめる。

  • Development of the spin frustration due to dynamical spin equilibrium and its induced successive magnetic phase transitions

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Project Year :

    2016.04
    -
    2019.03
     

    Kojima Norimichi, Enomoto Masaya

     View Summary

    We have synthesized (C6H5)4P[Zn(II)Fe(III)(mto)3](mto = C2O3S) consisting of Fe(III)O3S3 and Zn(II)O6 octahedra and investigated the spin state of the Fe(III) site. ESR and 57Fe Mossbauer spectra revealed that the rapid spin equilibrium in which the high spin state and the low spin state exchange in the time scale of 0.1 ns < τ < 0.1 μs occurs at the Fe(III) site. In the case of (C6H5)4P[Mn(II)Fe(III)(mto)3], there exists a rapid spin equilibrium (τ < 0.1 μs) between the high-spin and low-spin states at the Fe(III) site, which induces the frustration of internal magnetic field between the ferromagnetic and antiferromagnetic interactions at the Mn(II) site. Owing to the frustration of internal magnetic field at the Mn(II) site due to the rapid spin equilibrium at the Fe(III) site, (C6H5)4P[Mn(II)Fe(III)(mto)3] undergoes the successive magnetic phase transitions at 30 K and 23 K. At 30 K, only Mn(II) spin is ordered, while both of the Mn(II) and Fe(III) spins are ordered at 23 K.

  • 室温分子磁石を目指したマルチラジカル配位子の開発と多核高スピン錯体の構築

    文部科学省  科学研究費補助金(若手研究(B))

    Project Year :

    2015
    -
    2016
     

    岡澤 厚

  • 希土類フリーな硬質分子磁石の創製を目指した基盤的研究

    公益社団法人新化学技術推進協会  第3回新化学技術研究奨励賞

    Project Year :

    2014.07
    -
    2015.03
     

    岡澤 厚

  • Development of Supramolecular Magnets toward Multifunction Materials

    Ministry of Education, Culture, Sports, Science and Technology  Grants-in-Aid for Scientific Research(基盤研究(C))

    Project Year :

    2007
    -
    2009
     

    Takayuki ISHIDA, Atsushi OKAZAWA

     View Summary

    We developed novel organic-inorganic hybrid magnets showing biand multifunctionality.(1) Low-dimensional magnets : The hardest magnet (magnet showing the highest coercivity) was characterized from cobalt-radical one-dimensional heterospin systems.(2) Supramolecular magnets : Paramagnetic host compounds were prepared, and their magnetic properties were tuned by means of supramolecular chemistry.(3) Mesophase and liquid-crystalline magnets : Several iron (II) coordination compounds having long alkyl chains were synthesized, and the coexistence of mesophase transition and spin-crossover transi...

  • Systematic Development of Behavior for Lanthanoid-Transition-Metal Single-Molecule Magnets

    Ministry of Education, Culture, Sport, Science and Technology  Grants-in-Aid for Young Scientists (B)

    OKAZAWA, Atsushi

     View Summary

    We developed novel rare-earth and transition-metal heterometallic complexes, which show single-molecule magnet behavior, and elucidated their magnetic couplings.As for trinuclear complexes [DyMDy] (M = Pd, Cu, Ni), single-molecule magnet performance was enhanced with increasing the spin quantum numbers of M ions. The [DyNiDy]-type complex with the methylimidazole ligands at the axial positions showed high performance compared to the complex having the pyridine ligands, which is due to a difference of coordination geometries around the Dy ions.In addition, we demonstrated the chemical trends of magnetic coupling between rare-earth and transition-metal spins for [LnCu], [LnV], [CuLnCu], [Ln4Cu], and [Ln2Cu2]n.

▼display all

Misc

  • スピン平衡を示す鉄(II)錯体のメスバウアー分光およびミュオン分光からみた動的挙動

    小林弘明, 岡澤厚, 川崎郁斗, 渡邊功雄, 小島憲道

    KURRI KR   ( 195 ) 23 - 26  2014.03

    J-GLOBAL

  • 直線型二配位鉄錯体のメスバウアー分光研究(III)

    小林義男, 松尾司, 伊藤幹直, 長友傑, 中村仁, 森雅樹, 岡澤厚, 小島憲道, 玉尾皓平

    KURRI KR   ( 168 ) 57 - 60  2012.02

    J-GLOBAL

  • ベルダジルラジカルが配位した新奇鉄(II)錯体[FeII(vdco)2(H2O)2]・2H2Oの結晶構造と物性:水分子の配向挙動に起因する57Feメスバウアースペクトルの異常な振舞いの解明

    亀渕萌, 岡澤厚, 榎本真哉, 原田潤, 小川桂一郎, 大久保將史, 丸田悟朗, 武田定, 小島憲道

    KURRI KR   ( 168 ) 51 - 56  2012.02

    J-GLOBAL

  • (C6H5)4P[Mn(II)Fe(III)(mto)3](mto=C2O3S)における速いスピン平衡と多段階磁気相転移の協奏現象

    影澤幸一, 岡澤厚, 榎本真哉, 小島憲道

    KURRI KR   ( 159 ) 53 - 58  2011.02

    J-GLOBAL

  • 25aPS-57 Magnetic structure changes of Prussian blue analogues during K-ion extraction

    Asakura D., Okubo M., Kudo T., Zhou H. S., Mizokawa T., Okazawa A., Kojima N.

    Meeting abstracts of the Physical Society of Japan   65 ( 2 ) 412 - 412  2010.08

    CiNii

  • 鉄混合原子価錯体(n‐CnH2n+1)4N[FeIIFeIII(mto)3](n=3,4;mto=C2O3S)における速いスピン平衡と電荷揺動の協奏現象

    影澤幸一, 岡澤厚, 榎本真哉, 小島憲道

    KURRI KR   ( 152 ) 19 - 22  2010.03

    J-GLOBAL

  • 27aQJ-11 Exchange coupling and magnetism of RE-3d hetero-metallic magnetic molecule

    Nojiri H, Hayashi M, Tanaka G, Yoshii S, Gomella A, Ishida T, Okazawa A

    Meeting abstracts of the Physical Society of Japan   64 ( 2 ) 368 - 368  2009.08

    CiNii

  • 20aQH-7 Magnetism and Exchange Interaction in RE-3d Heterometallic Molecular Magnet

    Nojiri H., Yoshii S., Ishida T., Okazawa A.

    Meeting abstracts of the Physical Society of Japan   63 ( 2 ) 359 - 359  2008.08

    CiNii

  • HF‐EPR測定を用いた希土類イオン―遷移金属イオン間の交換相互作用定数の決定

    岡澤厚

    電子スピンサイエンス   ( 10 ) 41 - 42  2008.03

    J-GLOBAL

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Syllabus

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Teaching Experience

  • 理工学基礎実験IA, IB

    早稲田大学  

    2022.04
    -
    Now
     

  • 自然科学実験II

    日本大学医学部  

    2020.09
    -
    2022.03
     

  • 医系化学

    日本大学医学部  

    2020.04
    -
    2022.03
     

  • 基礎化学実験

    東京大学  

    2014.09
    -
    2020.03
     

  • 物質科学実験I, II

    東京大学  

    2013.04
    -
    2020.03
     

  • 基礎科学実験IA, IB, II, III

    東京大学  

    2009.09
    -
    2013.03
     

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Research Institute

  • 2022
    -
    2024

    Waseda Center for a Carbon Neutral Society   Concurrent Researcher

Internal Special Research Projects

  • ラジカル遷移金属錯体によるレドックスフロー電池用電解液の開発

    2023   角地 貴行, 郅 東澤, 小岩 浩太郎

     View Summary

     再生可能エネルギーを電力系統に導入するためには、大規模な定置型蓄電システムが必要となり、その有力候補のひとつとしてレドックスフロー電池が注目されている。しかし、実用化されているバナジウム系は腐食性の硫酸溶液や資源制約の強いバナジウムの利用が問題となっている。そこで我々は、資源制約フリーな有機物や鉄系金属錯体を正極液活物質として利用し、包括的な電池性能(エネルギー密度・サイクル特性、クーロン効率など)の向上を目指してきた。特に、電解液中活物質の溶解度を高めることは電池の体積エネルギー密度に直結するため、非常に重要な技術といえる。 本研究では非水系レドックスフロー電池用の正極液活物質の候補として、約1 V (vs.SHE)程度の高い酸化還元電位を有するターピリジン鉄錯体の溶解度を改善する手法の開発を進めてきた。(1)配位子上にポリエチレングリコール系置換基を導入、および(2)分子の非対称化および活物質の混合、の方法によって、無置換体[Fe(tpy)2](PF6)2の溶解度0.16 M(アセトニトリル溶媒)から最大で0.68 Mまで溶解度を向上させることに成功した。これは、いわば活物質の多成分化による溶解度向上の新規手法であり、活物質依存性の少ない汎用的なものだと期待される。また、水に溶解しないため見向きされてこなかった分子性活物質に対して、高濃度LiTFSI水溶液を用いて溶解させた水系電解液の開発も検討した。近年、TEMPOラジカルを高濃度水系電解液に用いる手法が開発されたので、我々はこれを応用してTEMPOの4-位にケトン基の付いた誘導体が同様に34 Mまで溶解することを見出した。今後、資源制約フリーな電解液によるレドックスフロー電池の高エネルギー密度化が期待される。

  • 機械学習を活用したレドックスフロー電池の活物質開発と溶解度の化学

    2022   角地 貴行, 大久保 將史

     View Summary

     再生可能エネルギーを大規模電力網の中で活用するための蓄電システムとしてレドックスフロー電池が注目されている。しかし、実用化されているバナジウム系は硫酸溶液やレアメタル使用のため普及が進んでおらず、改良の余地が多く残されている。そこで本研究では、資源豊富な鉄系金属錯体を正極液活物質として利用し、包括的な電池性能(エネルギー密度・サイクル特性、クーロン効率など)の向上に対する分子設計指針を得ることを目的とした。特に電極液の高エネルギー密度化は重要であるが、本研究では(1)正極液の分子非対称性化、(2)配位子上への置換基導入の両方法によって、無置換体鉄錯体と比べてそれぞれ約3倍程度も溶解度を向上させることに成功し、重要な分子設計指針を示すことができた。

  • ヘテロレプティック金属錯体における溶解性とレドックス特性の評価

    2022  

     View Summary

     再生可能エネルギーを大規模電力網の中で活用するための蓄電システムとしてレドックスフロー電池が注目されている。しかし、実用化されているバナジウム系は硫酸溶液やレアメタル使用のため普及が進んでおらず、改良の余地が多く残されている。そこで本研究では、資源豊富な鉄系金属錯体を正極液活物質として利用し、包括的な電池性能(エネルギー密度・サイクル特性、クーロン効率など)の向上に対する分子設計指針を得ることを目的とした。特に電極液の高エネルギー密度化は重要であるが、本研究では(1)正極液の分子非対称性化、(2)配位子上への置換基導入の両方法によって、無置換体鉄錯体と比べてそれぞれ約3倍程度も溶解度を向上させることに成功し、重要な分子設計指針を示すことができた。