研究者データベース

加藤 優(カトウ マサル)
地球環境科学研究院 物質機能科学部門 分子材料化学分野
准教授

基本情報

所属

  • 地球環境科学研究院 物質機能科学部門 分子材料化学分野

職名

  • 准教授

学位

  • 博士(理学)(埼玉大学)

ORCID ID

J-Global ID

研究キーワード

  • タンパク質フィルム電気化学   電気化学   電極触媒   

研究分野

  • ナノテク・材料 / 無機・錯体化学

研究活動情報

論文

  • Abinash Chandro Sarker, Masaru Kato, Ichizo Yagi
    Electrochimica Acta 425 140628 - 140628 2022年09月 
    We report the preparation of Pt and/or Pd nanoparticle-deposited fluorine-doped tin oxide (FTO) electrodes by an arc-plasma deposition (APD) technique and their electrocatalytic activity for nitrate (NO3–), nitrite (NO2–), nitric oxide (NO), and nitrous oxide (N2O) reduction reactions in acidic media. Cyclic voltammetry of the electrodes revealed that the co-presence of Pt and Pd on FTO showed higher catalytic activity than Pt or Pd on FTO for the NO3– reduction reaction, where the PtPd/Sn interface acts as the catalytic active site. The PtPd/Sn interface also showed higher catalytic activity for the N2O reduction reaction to dinitrogen than the Pt/Sn or Pd/Sn interfaces, whereas it showed no drastic contribution to the electrocatalytic NO2– and NO reduction reactions. Because the NO3– and N2O reduction reaction occur in the potential region of hydrogen adsorption on Pt and Pd electrodes, the PtPd/Sn interface could enhance NO3– and N2O adsorption and/or suppress the hydrogen adsorption. Our findings will be useful for the design of interfaces between noble metal mixture/alloy nanoparticles and Sn, leading to the practical application of denitrification to harmless dinitrogen.
  • Akinobu Yamaguchi, Naoya Akamatsu, Shunya Saegusa, Ryo Nakamura, Yuichi Utsumi, Masaru Kato, Ichizo Yagi, Tomoko Ishihara, Masaki Oura
    RSC Advances 12 17 10425 - 10430 2022年04月 
    The electrochemical Ni deposition at a platinum electrode was investigated in a plating nickel bath in the presence and absence of ethylene glycol (EG) using fluorescence yield soft X-ray absorption spectroscopy (FY-XAS) in the Ni L2,3-edge and O K-edge regions under potential control. At ≤+0.35 V vs. the reversible hydrogen electrode (RHE), the electrochemical Ni deposition was detected by the Ni L2,3-edge FY-XAS in the presence of EG whereas almost no such event was observed in the absence of EG. A drastic decrease of FY-XAS intensities in the O K-edge region was also observed in the presence of EG at >+0.35 V vs. RHE, suggesting that the nano-/micro-structured Ni deposition initiated by the removal of water molecules occurs on the Pt electrode. The complex formation of Ni2+ with EG and the adsorption of EG on the Ni surface could play an important role in the Ni deposition. This study demonstrates that the in situ FY-XAS is a powerful and surface-sensitive technique to understand (electro)chemical reactions including polyol synthesis and electrocatalysis at solid-liquid interfaces.
  • Koki Matsumoto, Masaru Kato, Ichizo Yagi, Siqi Xie, Kiyotaka Asakura, Shin-ichiro Noro, Norimitsu Tohnai, Stéphane Campidelli, Takashi Hayashi, Akira Onoda
    28 e202103545  2022年 [査読有り][通常論文]
  • Masaru Kato, Yoshimi Iguchi, Tianchi Li, Yuta Kato, Yu Zhuang, Kotaro Higashi, Tomoya Uruga, Takahiro Saida, Keiko Miyabayashi, Ichizo Yagi
    ACS Catalysis 12 259 - 264 2021年12月15日 [査読有り][通常論文]
     
    We report the preparation, oxygen reduction reaction (ORR) electrocatalytic activity, and structural transformation of Pt-Ni nanowires (NWs) during potential cycles in the presence and absence of Pt-Ni nanoparticles (NPs). The ORR activity of NWs increases over 25000 potential cycles in the presence of NPs, involving the structural transformation of NWs to branched nanostructures assisted by Ostwald ripening of NPs. This structural transformation is coupled with the surface electronic structural change, as confirmed by in situ X-ray absorption spectroscopy and carbon monoxide stripping voltammetry, leading to catalytic activity improvement and Pt dissolution suppression. Although a similar structural transformation was also observed even in the absence of NPs, greater amounts of Pt were dissolved during potential cycles. These results indicate that the structural transformation is intrinsic to Pt-based NWs but the structural transformation of NWs assisted by Ostwald ripening of NPs is beneficial to suppress the Pt dissolution. The concept of the structural optimization of nanostructured catalysts assisted by Ostwald ripening of NPs under potential cycles will guide us to develop highly active and durable Pt-based electrocatalysts and phase-engineered nanomaterials.
  • Masaru Kato, Yuki Unuma, Manabu Okui, Yunteng Qu, Jinhang Zheng, Satoshi Taguchi, Fumiya Kiguchi, Mashu Torihata, Yunzhi Gao, Nagahiro Hoshi, Ichizo Yagi
    Electrochimica Acta 139281 - 139281 2021年12月 [査読有り]
  • Satoshi Yasuda, Kazuhisa Tamura, Masaru Kato, Hidehito Asaoka, Ichizo Yagi
    The Journal of Physical Chemistry C 125 22154 - 22162 2021年10月04日
  • Masaru Kato, Yuya Masuda, Narumi Yoshida, Takehiko Tosha, Yoshitsugu Shiro, Ichizo Yagi
    Electrochimica Acta 373 137888 - 137888 2021年03月 [査読有り]
  • Masaru Kato, Natsuki Fujibayashi, Daiki Abe, Naohiro Matsubara, Satoshi Yasuda, Ichizo Yagi
    ACS Catalysis 11 2356 - 2365 2021年02月19日 [査読有り][通常論文]
  • Masaru Kato, Yukatsu Shichibu, Kazuya Ogura, Mitsuhiro Iwasaki, Mizuho Sugiuchi, Katsuaki Konishi, Ichizo Yagi
    The Journal of Physical Chemistry Letters 11 19 7996 - 8001 2020年10月01日 [査読有り][通常論文]
  • Masaru Kato, Ryota Nakahoshiba, Kazuya Ogura, Shoichi Tokuda, Satoshi Yasuda, Kotaro Higashi, Tomoya Uruga, Yohei Uemura, Ichizo Yagi
    ACS Applied Energy Materials 2020年07月27日 [査読有り][通常論文]
  • Masaru Kato
    e-Journal of Surface Science and Nanotechnology 18 81 - 93 2020年03月14日 [査読有り][通常論文]
     
    Polymer electrolyte fuel cells (PEFCs) are a clean, sustainable device to convert chemical energy to electricity and can provide power for automobiles, trains, and ships. In PEFCs, the oxygen reduction reaction (ORR) occurs at the cathode and is catalyzed at electrocatalysts. The activity of ORR electrocatalysts is known to limit the overall performance of PEFCs because the ORR is more sluggish than the hydrogen oxidation reaction at the anode. In the state-of-the-art PEFC, platinum group metal (PGM)-based ORR electrocatalysts are used. Since PGMs are rare and expensive, highly active and durable non-PGM ORR electrocatalysts are required for widespread applications of PEFCs. In nature, metalloenzymes such as cytochrome c oxidase and multicopper oxidases efficiently catalyze the ORR and utilize multinuclear iron and/or copper complexes as active sites. The structure of these active sites and enzyme reaction mechanisms would give us design concepts of artificial non-PGM electrocatalysts for the ORR, possibly leading us to develop next-generation non-PGM electrocatalysts. Herein, recent research progress on understanding enzymatic ORR reaction mechanisms and developing non-PGM ORR electrocatalysts is reviewed from the viewpoint of bio-inspired approaches.
  • Satoshi Yasuda, Kazuhisa Tamura, Tomo-o Terasawa, Masahiro Yano, Hideaki Nakajima, Takahiro Morimoto, Toshiya Okazaki, Ryuushi Agari, Yasufumi Takahashi, Masaru Kato, Ichizo Yagi, Hidehito Asaoka
    The Journal of Physical Chemistry C 124 9 5300 - 5307 2020年03月05日 [査読有り][通常論文]
     
    Confinement of hydrogen molecules at graphene-substrate interface has presented significant importance from the viewpoints of development of fundamental understanding of two-dimensional material interface and energy storage system. In this study, we investigate H-2 confinement at a graphene-Au interface by combining selective proton permeability of graphene and the electrochemical hydrogen evolution reaction (electrochemical HER) method. After HER on a graphene/Au electrode in protonic acidic solution, scanning tunneling microscopy finds that H-2 nanobubble structures can be produced between graphene and the Au surface. Defect dependence of the bubble formation suggests that intrinsic defects in graphene, which have high hydrogen permeation barrier but are permeable for protons, are involved in the fundamental mechanism of bubble formation. Strain analysis by Raman spectroscopy also shows that atomic size roughness on the graphene/Au surface originating from the HER-induced strain relaxation of graphene plays significant role in formation of the nucleation site and H-2 storage capacity. The result presented herein would provide further understanding of molecular confinement at graphene-based interface and development of novel energy material.
  • Real-Time Monitoring of Low Pressure Oxygen Molecules over Wide Temperature Range: Feasibility of Ultrathin Hybrid Films of Iridium(III) Complexes and Clay Nanosheets
    Hisako Sato, Kazuyoshi Takimoto, Masaru Kato, Shin-ichi Nagaoka, Kenji Tamura, Akihiko Yamagishi
    Bull. Chem. Soc. Jpn. 93 doi:10.1246/bcsj.20190277 194 - 199 2020年 [査読有り][通常論文]
  • Masaru Kato, Keita Kon, Jun Hirayama, Ichizo Yagi
    New Journal of Chemistry 43 25 10087 - 10092 2019年 [査読有り][通常論文]
  • Masaru Kato, Ai Araki, Yuki Hara, Satoshi Taguchi, Ichizo Yagi
    Electrochemistry 86 5 220 - 222 2018年08月 [査読有り][通常論文]
  • Masaru Kato, Shogo Nakagawa, Takehiko Tosha, Yoshitsugu Shiro, Yuya Masuda, Kou Nakata, Ichizo Yagi
    The Journal of Physical Chemistry Letters 9 5195 - 5200 American Chemical Society ({ACS}) 2018年08月 [査読有り][通常論文]
  • Masaru Kato, Kazuya Ogura, Shogo Nakagawa, Shoichi Tokuda, Kiyonori Takahashi, Takayoshi Nakamura, Ichizo Yagi
    ACS Omega 3 8 9052 - 9059 2018年08月 [査読有り][通常論文]
     
    Pt-based nanostructured electrocatalysts supported on carbon black have been widely studied for the oxygen reduction reaction (ORR), which occurs at the cathode in polymer electrolyte fuel cells. Because sluggish ORR kinetics are known to govern the cell performance, there is a need to develop highly active and durable electrocatalysts. The ORR activity of Pt-based electrocatalysts can be improved by controlling their morphology and alloying Pt with transition metals such as Ni. Improving the catalyst durability remains challenging and there is a lack of catalyst design concepts and synthetic strategies. We report the enhancement of the ORR activity and durability of a nanostructured Pt-Ni electrocatalyst by strong metal/support interactions with a nitrogen-doped carbon (NC) support. Pt-Ni rhombic dodecahedral nanoframes (NFs) were immobilized on the NC support and showed higher ORR electrocatalytic activity and durability in acidic media than that supported on a nondoped carbon black. Durability tests demonstrated that NF/NC showed almost no activity loss even after 50 000 potential cycles under catalytic conditions, and the Ni dissolution from the NFs was suppressed at the NC support, as confirmed by, energy dispersive X-ray spectroscopy analysis. Physicochemical measurements including surface-enhanced infrared absorption spectroscopy of surface-adsorbed CO revealed that the strong metal/support interactions of the NF with the NC support caused the downshift of the d-band center position of the surface Pt. Our findings demonstrate that tuning the electronic structure of nanostructured Pt alloy electrocatalysts via the strong metal/support interactions with heteroatom-doped carbon supports will allow the development of highly active and robust electrocatalysts.
  • Masaru Kato, Marika Muto, Naohiro Matsubara, Yohei Uemura, Yuki Wakisaka, Tsubasa Yoneuchi, Daiju Matsumura, Tomoko Ishihara, Takashi Tokushima, Shin-ichiro Noro, Satoru Takakusagi, Kiyotaka Asakura, Ichizo Yagi
    ACS Applied Energy Materials 1 5 2358 - 2364 American Chemical Society ({ACS}) 2018年05月 [査読有り][通常論文]
     
    Multinuclear metal active sites are widely used as catalytic reaction centers in metalloenzymes and generally show high catalytic activity. For example, laccases are known to catalyze the oxygen reduction reaction (ORR) to water at a multinuclear copper site with almost no energy loss. The ORR is an important reaction not only in oxygenic respiration but also in future energy generation devices such as polymer electrolyte fuel cells and metal-air batteries. For large-scale commercialization of these devices, there is a need to develop highly active ORR electrocatalysts based on nonprecious metals. Incorporation of multinuclear metal active sites in conductive materials such as carbon will allow us to develop highly active electrocatalysts like metalloenzymes. However, such methods had not been established yet. Herein, we report a copper-based ORR electrocatalyst with multinuclear copper active sites in nitrogen-doped graphene. The electrocatalyst was synthesized from the mixture of graphene oxide and a multinuclear copper complex in a short-period heating method. Electrochemical measurements revealed that the obtained electrocatalyst showed the highest electrocatalytic activity for the ORR in the Cu-based electrocatalysts in neutral aqueous solution. Physicochemical measurements including in situ X-ray absorption spectroscopy revealed the incorporation of multinuclear copper sites. Our synthetic approach will offer guidance for developing highly active electrocatalysts utilizing multinuclear metal sites not only for the ORR but also for other electrocatalytic reactions.
  • 表面増強赤外吸収分光法による電極/溶液界面における反応計測
    八木一三, 加藤優, 中田耕, 中川省吾
    分光研究 67 2 41 - 56 2018年04月 [査読有り][通常論文]
  • Masaru Kato, Hisako Sato, Ichizo Yagi, Miwa Sugiura
    Electrochimica Acta 264 386 - 392 2018年02月20日 [査読有り][通常論文]
     
    Photosynthesis converts solar energy into chemical energy. Photosystem II (PSII) oxidizes water to produce oxygen, electrons and protons under solar light irradiation. This light-driven water oxidation initiates a series of reactions in photosynthesis. Basic photoelectrochemical studies on PSII are directed toward the enzymatic applications of PSII for sustainable production of electricity or solar fuels. To maximize the photoelectrochemical catalytic activity of PSII on electrode substrates, interfacial designs between PSII and electrode substrates are important. Herein, we report bio-inorganic photoanodes of PSII and ferricyanide-intercalated layered double hydroxide (LDH) for visible-light-driven water oxidation. PSII is simply drop-cast onto a ferricyanide-intercalated cobalt–aluminum LDH and then shows a turnover frequency of 0.5 ± 0.1 s−1 and a turnover number of 920 ± 40 for 1 h at pH 6.5 at +0.5 V vs. NHE under visible light irradiation. Photoelectrochemical experiments using a PSII inhibitor or a bio-engineered PSII suggest that interfacial electron transfer from the plastoquinone QA site of PSII to ferricyanide may play an important role in improving the photo-electrocatalytic activity and stability of PSII. Our studies will open up new possibilities in fundamental or advanced photoelectrochemical studies of PSII.
  • Tomoko Ishihara, Takashi Tokushima, Yuka Horikawa, Masaru Kato, Ichizo Yagi
    REVIEW OF SCIENTIFIC INSTRUMENTS 88 10 104101  2017年10月 [査読有り][通常論文]
     
    We developed a spectro-electrochemical cell for X-ray absorption and X-ray emission spectroscopy, which are element-specific methods to study local electronic structures in the soft X-ray region. In the usual electrochemical measurement setup, the electrode is placed in solution, and the surface/interface region of the electrode is not normally accessible by soft X-rays that have low penetration depth in liquids. To realize soft X-ray observation of electrochemical reactions, a 15-nm-thick Pt layer was deposited on a 150-nm-thick film window with an adhesive 3-nm-thick Ti layer for use as both the working electrode and the separator window between vacuum and a sample liquid under atmospheric pressure. The designed three-electrode electrochemical cell consists of a Pt film on a SiC window, a platinized Pt wire, and a commercial Ag vertical bar AgCl electrode as the working, counter, and reference electrodes, respectively. The functionality of the cell was tested by cyclic voltammetry and X-ray absorption and emission spectroscopy. As a demonstration, the electroplating of Pb on the Pt/SiC membrane window was measured by X-ray absorption and real-time monitoring of fluorescence intensity at the O 1s excitation. Published by AIP Publishing.
  • Masaru Kato, Manabu Okui, Satoshi Taguchi, Ichizo Yagi
    JOURNAL OF ELECTROANALYTICAL CHEMISTRY 800 46 - 53 2017年09月 [査読有り][通常論文]
     
    Nitrate anion is one of the main nitrogen-containing-pollutants in groundwater and can be removed" using denitrification systems including electrocatalytic systems. Herein we report on electrocatalytic nitrate reduction catalyzed on tin-modified single crystalline electrodes of palladium, platinum and palladium-platinum alloy in acidic and neutral media. We have prepared electrodes with the (111) surface or the (100) surface and modified their surface with tin. Cyclic voltammetry of the electrodes has revealed that the tin-modified alloy (trimetallic) electrodes show higher electrocatalytic activity than the tin-modified platinum or palladium (bimetallic) electrodes, and the catalytic reaction is more efficiently catalyzed on the (100) surface rather than the (111) surface. The tin-modified PdPt(100) electrode shows the highest catalytic activity in acidic media as well as in neutral media. X-ray photoelectron spectroscopy suggests that metallic tin forms on the (100) surface, but divalent tin species on the (111) surface, indicating that a surface alloy of tin may form on the (100) surface, resulting in enhancement of the electrocatalytic activity. Our findings suggest that design and preparation of ternary metallic electrodes with the (100) surface will pave the way to the development of practical systems on electrocatalytic denitrification. (C) 2017 Elsevier B.V. All rights reserved.
  • Masaru Kato, Takeshi Murotani, Ichizo Yagi
    CHEMISTRY LETTERS 45 10 1213 - 1215 2016年10月 [査読有り][通常論文]
     
    We report an Fe/Cu/N-doped carbon electrocatalyst for the oxygen reduction reaction to water. Pyrolysis of metal precursors supported on oxidized carbon black provides the electrocatalyst with high catalytic activity and selectivity. Detailed physical-chemical studies have revealed that the. copresence of iron and copper catalytic sites in carbon in a 1:1 mole ratio, which is the same as that of an enzyme of cytochrome c oxidase, might be the key to synthesize highly active and selective electrocatalysts.
  • Masaru Kato, Nobuhisa Oyaizu, Katsuaki Shimazu, Ichizo Yagi
    JOURNAL OF PHYSICAL CHEMISTRY C 120 29 15814 - 15822 2016年07月 [査読有り][招待有り]
     
    We report two-dimensional model systems to study the electrocatalytic activities of dinuclear copper complexes for various electrocatalytic reactions including the oxygen reduction reaction (ORR), where we can use electrochemical techniques as well as surface-sensitive techniques such as X-ray photoelectron spectroscopy and vibrational sum frequency generation spectroscopy. Heteroaromatic thiols, including four triazoles and a thiadiazole, are used as metal ligands as well as anchors to a polycrystalline gold electrode. The thiols are self-assembled on the polycrystalline gold electrode and then react with copper(II) ions to give monolayers of copper-based ORR catalysts on the surface. The dinuclear copper complexes of 1,2,4-triazole-3-thiol and 3-amino-1,2,4-triazole-5-thiol show ORR activity and pH-dependent catalytic behavior similar to that of counterparts supported on carbon black, suggesting that our two-dimensional systems can serve as model catalysts for carbon-supported molecular catalysts. We have also self-assembled dinuclear copper complexes with long alkyl or perfluoroalkyl chains on the surface and studied their orientation on the surface and oxygen transport.
  • 武藤 毬佳, 加藤 優, 八木 一三
    表面科学学術講演会要旨集 35 359 - 359 公益社団法人 日本表面科学会 2015年 
    固体高分子形燃料電池の酸素還元電極触媒として、現在白金族金属が用いられている。しかし、白金の埋蔵量の少なさゆえにコスト面で問題を抱えているため、安価かつ高活性な非白金系酸素還元電極触媒の開発が望まれている。そこで、三角形配置銅三核錯体をカーボンに組み込むことに着目し、高温加熱処理により酸素還元電極触媒を新たに調製した。本発表では、その合成条件の検討結果や酸素還元触媒活性について報告する。
  • 加藤 優, 君島 堅一, 柴田 真里, 野津 英男, 荻野 和也, 猪熊 喜芳, 太田 鳴海, 小柳津 暢久, 上原 広充, 大場 惟史, 上村 洋平, 高草木 達, 朝倉 清高, 八木 一三
    表面科学学術講演会要旨集 35 357 - 357 公益社団法人 日本表面科学会 2015年 
    固体高分子形燃料電池の酸素還元電極触媒としては主に白金系合金が用いられているが、埋蔵量やコスト面に問題を抱えているため、安価かつ高活性な非白金系酸素還元電極触媒の開発が近年盛んに行われている。本発表では、銅系酸素還元電極触媒の中で特に高い触媒活性を示す銅二核錯体触媒に着目し、その高い触媒活性を示す理由を解明するためにin situ XAFS測定を行ったので、その結果に関して報告する。
  • Masaru Kato, Ken'ichi Kimijima, Mari Shibata, Hideo Notsu, Kazuya Ogino, Kiyoshi Inokuma, Narumi Ohta, Hiromitsu Uehara, Yohei Uemura, Nobuhisa Oyaizu, Tadashi Ohba, Satoru Takakusagi, Kiyotaka Asakura, Ichizo Yagi
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 14 8638 - 8641 2015年 [査読有り][通常論文]
     
    A dinuclear copper(II) complex of 3,5-diamino-1,2,4-triazole is one of the highly active copper-based catalysts for the oxygen reduction reaction (ORR) in basic solutions. Our in situ X-ray absorption near edge structure measurements revealed that deprotonation of the triazole ligand might cause coordination geometrical changes, resulting in the enhancement of the ORR activity.
  • Hisako Sato, Miwa Ochi, Masaru Kato, Kenji Tamura, Akihiko Yamagishi
    NEW JOURNAL OF CHEMISTRY 38 12 5715 - 5720 2014年12月 [査読有り][通常論文]
     
    Multi-layered hybrid films comprised of amphiphilic cationic iridium(III) complexes and the exfoliated layers of synthetic saponite were prepared by the modified Langmuir-Blodgett method. Two iridium(III) complexes, [Ir(dfppy)(2)(dc9bpy)](+) (dfppyH = 2-(4',6'-difluorophenyl)pyridine; dc9bpy = 4,4'-dinonyl-2,2'-bipyridine) and [Ir(dfppy)(2)(dc9bpy)(+) (piqH = 1-phenyisoquinoline), were used as blue (donor) and red emitters (acceptor), respectively. A non-luminescent hybrid layer of stearylammonium and synthetic saponite was deposited in a layer-by-layer manner to vary the distance between the donor and acceptor layers. Energy transfer was analysed according to the Forster-type mechanism with a focus on the dependence of its efficiency on the interlayer distance.
  • Masaru Kato, Jenny Z. Zhang, Nicholas Paul, Erwin Reisner
    CHEMICAL SOCIETY REVIEWS 43 18 6485 - 6497 2014年09月 [査読有り][通常論文]
     
    Photosynthesis is responsible for the sunlight-powered conversion of carbon dioxide and water into chemical energy in the form of carbohydrates and the release of O-2 as a by-product. Although many proteins are involved in photosynthesis, the fascinating machinery of Photosystem II (PSII) is at the heart of this process. This tutorial review describes an emerging technique named protein film photoelectrochemistry (PF-PEC), which allows for the light-dependent activity of PSII adsorbed onto an electrode surface to be studied. The technique is straightforward to use, does not require highly specialised and/or expensive equipment, is highly selective for the active fractions of the adsorbed enzyme, and requires a small amount of enzyme sample. The use of PF-PEC to study PSII can yield insights into its activity, stability, quantum yields, redox behaviour, and interfacial electron transfer pathways. It can also be used in PSII inhibition studies and chemical screening, which may prove useful in the development of biosensors. PSII PF-PEC cells also serve as proof-of-principle solar water oxidation systems; here, a comparison is made against PSII-inspired synthetic photocatalysts and materials for artificial photosynthesis.
  • Keiji Ohno, Tomoaki Sugaya, Masaru Kato, Noriko Matsumoto, Ryoko Fukano, Yasuyo Ogino, Sumio Kaizaki, Takashi Fujihara, Akira Nagasawa
    CRYSTAL GROWTH & DESIGN 14 8 3675 - 3679 2014年08月 [査読有り][通常論文]
     
    Hydrous crystals of [{Pd-II(bpy)}(2)(mu-x-tart)]. nH(2)O (bpy: 2,2'-bipyridine; tartH(2)(2-): tartrate; 1a: x = L, n = 6; 2a: x = D, n = 6; 3a: x = DL, n = 4; 4a: x = meso, n = 4) and anhydrous crystals of [{Pd-II(bpy)}(2)(mu-L-tart)] (1b) were isolated from aqueous and MeOH solutions, respectively. X-ray crystallography revealed the stacked structures of clamshell-like dinuclear units in 1a-3a and 1b, where intramolecular metal metal and pi-pi stacking interactions were observed. Right- and left-handed helically stacked columns were formed in the 1a and 2a crystals, respectively. The significant role of hydrogen bonding among lattice water molecules and tartrate is suggested because 1b exhibited a zigzag arrangement only through intermolecular metal-metal interactions. In 3a, L- and D-tart units stacked alternately in a zigzag arrangement with intermolecular pi-pi interactions. In 4a, dimeric aggregates of the twisted dinuclear units further formed a 2D sheet architecture.
  • Yi-Hsuan Lai, Masaru Kato, Dirk Mersch, Erwin Reisner
    FARADAY DISCUSSIONS 176 199 - 211 2014年 [査読有り][通常論文]
     
    This discussion describes a direct comparison of photoelectrochemical (PEC) water oxidation activity between a photosystem II (PSII)-functionalised photoanode and a synthetic nanocomposite photoanode. The semi-biological photoanode is composed of PSII from the thermophilic cyanobacterium Thermosynechococcus elongatus on a mesoporous indium tin oxide electrode (mesoITO| PSII). PSII embeds all of the required functionalities for light absorption, charge separation and water oxidation and ITO serves solely as the electron collector. The synthetic photoanode consists of a TiO2 and NiOx coated nanosheet-structured WO3 electrode (nanoWO(3)|TiO2|NiOx). The composite structure of the synthetic electrode allows mimicry of the functional key features in PSII: visible light is absorbed by WO3, TiO2 serves as a protection and charge separation layer and NiOx serves as the water oxidation electrocatalyst. MesoITO|PSII uses low energy red light, whereas nanoWO(3)|TiO2|NiOx requires high energy photons of blue-end visible and UV regions to oxidise water. The electrodes have a comparable onset potential at approximately 0.6 V vs. reversible hydrogen electrode (RHE). MesoITO|PSII reaches its saturation photocurrent at 0.84 V vs. RHE, whereas nanoWO(3)|TiO2|NiOx requires more than 1.34 V vs. RHE. This suggests that mesoITO|PSII suffers from fewer limitations from charge recombination and slow water oxidation catalysis than the synthetic electrode. MesoITO|PSII displays a higher 'per active' site activity, but is less photostable and displays a much lower photocurrent per geometrical surface area and incident photon to current conversion efficiency (IPCE) than nanoWO(3)|TiO2|NiOx.
  • Masaru Kato, Kei Unoura, Toshiyuki Takayanagi, Yasuhisa Ikeda, Takashi Fujihara, Akira Nagasawa
    INORGANIC CHEMISTRY 52 23 13375 - 13383 2013年12月 [査読有り][通常論文]
     
    Five metal complexes of 2-methylisothiazol-3(2H)-one (MIO), [Co-III(NH3)(5)(MIO)](3+), [Ru-II(NH3)(5)(MIO)](2+), [Ru-III(NH3)(5)(MIO)](3+), [(PtCl3)-Cl-II(MIO)](-), and trans-[(UO2)-O-VI(NO3)(2)(MIO)(2)], were synthesized, and their structures were determined by single-crystal X-ray crystallography. MIO is an ambidentate ligand and coordinates to metal centers through its oxygen atom in the cobalt(III), ruthenium(III), and uranium(VI) complexes and through its sulfur atom in the ruthenium(II) and platinum(III) complexes. This result suggests that MIO shows preferential behavior on its donating atoms. We also studied the electron-donor abilities of the oxygen and sulfur atoms of MIO. Various physical measurements on the conjugate acid of MIO and the MIO complexes allowed us to determine an acid dissociation constant (pK(a)) and donor number (DN) for the oxygen atom of MIO and Lever's electrochemical parameter (E-L) and a relative covalency parameter (k(L)) for the sulfur atom.
  • Masaru Kato, Tanai Cardona, A. William Rutherford, Erwin Reisner
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 135 29 10610 - 10613 2013年07月 [査読有り][通常論文]
     
    Photosystem II (PSII) offers a biological and sustainable route of photochemical water oxidation to O-2 and can provide protons and electrons for the generation of solar fuels, such as H-2. We present a rational strategy to electrostatically improve the orientation of PSII from a thermophilic cyanobacterium, Thermosynechococcus elongatus, on a nanostructured indium tin oxide (ITO) electrode and to covalently immobilize PSII on the electrode. The ITO electrode was modified with a self-assembled monolayer (SAM) of phosphonic acid ITO linkers with a dangling carboxylate moiety. The negatively charged carboxylate attracts the positive dipole on the electron acceptor side of PSII via Coulomb interactions. Covalent attachment of PSII in its electrostatically improved orientation to the SAM-modified ITO electrode was accomplished via an amide bond to further enhance red-light-driven, direct electron transfer and stability of the PSII hybrid photoelectrode.
  • Fezile Lakadamyali, Anna Reynal, Masaru Kato, James R. Durrant, Erwin Reisner
    CHEMISTRY-A EUROPEAN JOURNAL 18 48 15464 - 15475 2012年11月 [査読有り][通常論文]
     
    A visible-light driven H2 evolution system comprising of a RuII dye (RuP) and CoIII proton reduction catalysts (CoP) immobilised on TiO2 nanoparticles and mesoporous films is presented. The heterogeneous system evolves H2 efficiently during visible-light irradiation in a pH-neutral aqueous solution at 25 degrees C in the presence of a hole scavenger. Photodegradation of the self-assembled system occurs at the ligand framework of CoP, which can be readily repaired by addition of fresh ligand, resulting in turnover numbers above 300 molH2 (molCoP)-1 and above 200,000 molH2 (molTiO2 nanoparticles)-1 in water. Our studies support that a molecular Co species, rather than metallic Co or a Co-oxide precipitate, is responsible for H2 formation on TiO2. Electron transfer in this system was studied by transient absorption spectroscopy and time-correlated single photon counting techniques. Essentially quantitative electron injection takes place from RuP into TiO2 in approximately 180 ps. Thereby, upon dye regeneration by the sacrificial electron donor, a long-lived TiO2 conduction band electron is formed with a half-lifetime of approximately 0.8 s. Electron transfer from the TiO2 conduction band to the CoP catalysts occurs quantitatively on a 10 mu s timescale and is about a hundred times faster than charge-recombination with the oxidised RuP. This study provides a benchmark for future investigations in photocatalytic fuel generation with molecular catalysts integrated in semiconductors.
  • Masaru Kato, Tanai Cardona, A. William Rutherford, Erwin Reisner
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 134 20 8332 - 8335 2012年05月 [査読有り][通常論文]
     
    We report on a hybrid photoanode for water oxidation consisting of a cyanobacterial photosystem II (PSII) from Thermosynechococcus elongatus on a mesoporous indium-tin oxide (mesoITO) electrode. The three-dimensional metal oxide environment allows for high protein coverage (26 times an ideal monolayer coverage) and direct (mediator-free) electron transfer from PSII to mesoITO. The oxidation of water occurs with 1.6 +/- 0.3 mu A cm(-2) and a corresponding turnover frequency of approximately 0.18 +/- 0.04 (mol O-2) (mol PSII)(-1) s(-1) during red light irradiation. Mechanistic studies are consistent with interfacial electron transfer occurring not only from the terminal quinone Q(B), but also from the quinone Q(A) through an unnatural electron transfer pathway to the ITO surface.
  • Lakadamyali Fezile, Kato Masaru, Reisner Erwi
    Faraday Discussions 155 191 - 205 2012年 [査読有り][通常論文]
     
    This discussion describes a study of a particulate semiconductor assembly consisting of a photoactive ruthenium dye-sensitised metal oxide nanoparticle loaded with a synthetic cobaloxime proton reduction catalyst (CoP). The colloidal system evolves H-2 during visible light illumination in pH neutral aqueous solution in the presence of a sacrificial electron donor. The ruthenium photosensitiser (RuP) to cobaloxime loading ratio is simple to vary and optimise and a range of metal oxide nanoparticles were tested. A maximum photoactivity was identified with TiO2 nanoparticles modified with CoP and RuP in a 2 : 1 ratio in the colloidal reaction mixture: visible light irradiation yielded 600 +/- 32 mmol H-2 h(-1) (g TiO2)(-1). A total turnover number of 108 +/- 9 mol H-2 (mol CoP)(-1), the evolution of 4340 +/- 240 mu mol H-2 (g TiO2)(-1) and approximately 87 mu mol H-2 (m(2) TiO2)(-1) were observed after 10 h irradiation. Linkage of the catalysts to TiO2 is critical for the system to work efficiently, and CoP and RuP contain one and two phosphonic acid linker moieties, respectively. The novel phosphonate ester analogue of CoP, [CoCl(dimethylglyoximato)(2)(diethyl pyridyl-4-phosphonate)] (1) was also synthesised and studied. Complex 1 adsorbs only to a small extent to TiO2 and a reduced H-2 production rate (182 +/- 8 mmol H-2 h(-1) (g TiO2)(-1)) was observed when 1 was irradiated with RuP-modified TiO2. Thus, the lower TiO2 affinity of 1 results in a reduced photoactivity of the dispersion. The described semiconductor particles are also presented in the light of being advantageous over more established homogenous multi-component systems and supramolecular dyad complexes: the reported semi-heterogeneous system is straightforward to assemble and it works in a purely aqueous environment.
  • Fezile Lakadamyali, Masaru Kato, Nicoleta M. Muresan, Erwin Reisner
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 51 37 9381 - 9384 2012年 [査読有り][通常論文]
  • Masaru Kato, Shinjiro Izuka, Takashi Fujihara, Akira Nagasawa, Sigenao Kawai, Tomokazu Tanaka, Toshiyuki Takayanagi
    INORGANICA CHIMICA ACTA 370 1 304 - 310 2011年05月 [査読有り][通常論文]
     
    Structural and thermodynamic properties of biologically important metal-mugineic acid complexes have been studied from the theoretical side in order to understand the metal-chelating mechanism of phytosiderophore mugineic acid at an atomic level. Density-functional theory methods combined with the polarizable continuum model (PCM) have been employed to obtain free energies of complex formation and redox potentials for metal-mugineic acid complexes in solution. It has been found that the free energies of complex formation calculated at the B3LYP/PCM level of theory are in moderate agreement with available experimental results. The inclusion of explicit water molecules interacting with the carboxylic groups in deprotonated mugineic acid through strong hydrogen-bonds is found to further improve the calculated free energies of complex formation. (C) 2011 Elsevier B.V. All rights reserved.
  • Masaru Kato, Kazuo Hida, Takashi Fujihara, Akira Nagasawa
    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 4 495 - 502 2011年02月 [査読有り][通常論文]
     
    A dinuclear copper(II) complex, [{Cu(II)Cl(O-mi)}(2)(mu-Cl)(2)] [mi = 2-methylisothiazol-3(2H)-one], has been synthesized and its molecular structure in the solid state determined by single-crystal X-ray analysis. The crystal consists of centrosymmetric dinuclear copper(II) units in which each copper(II) ion is doubly bridged by two chloride ions and has a slightly distorted square-planar geometry with a terminal chlorido ligand and a terminal mi ligand coordinated through the oxygen atom. The dinuclear units stack one on top of another to form a one-dimensional two-leg ladder structure. The magnetic susceptibility of the powder was measured in the temperature range 3.0-302 K. It was found that there are ferromagnetic interactions along the rung (in the same direction of the intramolecule; J(rung) = +5.03 +/- 0.03 cm(-1)) and the leg (in the same direction of the intermolecule; J(leg) = +1.96 +/- 0.02 cm(-1)) and an antiferromagnetic interaction along the diagonal (J(x) = -1.36 +/- 0.02 cm(-1)), the experimental data being fitted by the numerical calculation for a twelve-site ladder Hamiltonian. In addition, DFT calculations with the UB3LYP functional on the model complex [{Cu(II)Cl(O-mi)}(2)(mu-Cl)(2)] gave an intramolecular magnetic coupling constant J = +28.6 cm(-1) and indicated that the spin-density distribution on O in mi is less than that on the terminal Cl. We conclude that the O-donor ligand at the terminal position plays an essential role in the emerging intramolecular ferromagnetic interaction.
  • Koichiro Takao, Masaru Kato, Shinobu Takao, Akira Nagasawa, Gert Bernhard, Christoph Hennig, Yasuhisa Ikeda
    INORGANIC CHEMISTRY 49 5 2349 - 2359 2010年03月 [査読有り][通常論文]
     
    The U(VI) complex with a pentadentate Schiff base ligand (N,N'-disalicylidenediethylenetriaminate = saldien(2-)) was prepared as a starting material of a potentially stable U(V) complex without any possibility of U(V)O(2)(+)center dot center dot center dot U(V)O(2)(+) cation-cation interaction and was found in three different crystal phases. Two of them had the same composition of U(VI)O(2)(saldien)center dot DMSO in orthorhombic and monoclinic systems (DMSO = dimethyl sulfoxide, 1a and 1c, respectively). The DMSO molecule in both 1a and 1c does not show any coordination to U(VI)O(2)(saldien), but it is just present as a solvent in the crystal structures. The other isolated crystals consisted only of U(VI)O(2)(saldien) without incorporation of solvent molecules (1b, orthorhombic). A different conformation of the coordinated saldien(2-) in 1c from those in 1a and 1b was observed. The conformers exchange each other in a solution through a flipping motion of the phenyl rings. The pentagonal equatorial coordination of U(VI)O(2)(saldien) remains unchanged even in strongly Lewis-basic solvents, DMSO and N,N-dimethylformamide. Cyclic voltammetry of U(VI)O(2)(saldien) in DMSO showed a quasireversible redox reaction without any successive reactions. The electron stoichiometry determined by the UV-vis-NIR spectroelectrochemical technique is close to 1, indicating that the reduction product of U(VI)O(2)(saldien) is [U(V)O(2)(saldien)](-), which is stable in DMSO. The standard redox potential of [U(V)O(2)(saldien)](-)/U(VI)O(2)(saldien) in DMSO is -1.584 V vs Fc/Fc(+). This U(V) complex shows the characteristic absorption bands due to f-f transitions in its 5f(1) configuration and charge-transfer from the axial oxygen to U(5+).
  • Koichiro Takao, Masaru Kato, Shinobu Takao, Akira Nagasawa, Andreas C. Scheinost, Gert Bernhard, Christoph Hennig, Yasuhisa Ikeda
    ACTINIDES 2009 9 1 2010年 [査読有り][通常論文]
     
    A U(VI) complex with N,N'-disalicylidenediethylenetriaminate (saldien(2-)) was characterized by single crystal X-ray analysis and X-ray absorption fine structure (XAFS) spectroscopy, and its electrochemical behavior in a DMSO solution was studied. The obtained U(VI)-saldien(2-) complex recrystallized from DMSO was identified as orthorhombic (UO2)-O-VI(saldien)center dot DMSO. All coordination sites in the equatorial plane of UO22+ are occupied by coordinating O and N atoms of saldien(2-). Comparing a k(3)-weighted U L-III-edge EXAFS spectra of (UO2)-O-VI(saldien) in DMSO and DMF solutions with that in solid state, the molecular structure of (UO2)-O-VI(saldien) remains even in the solutions. Quasi-reversible redox waves of (UO2)-O-VI(saldien) were observed at E degrees = -1.582 +/- 0.005 V vs. Fc/Fc(+) (Delta E-p = 0.080-0.170 V at v = 0.010-0.500 V.s(-1)) in DMSO. UV-Vis-NIR absorption spectral change with the electrochemical reduction of (UO2)-O-VI(saldien) using the spectroelectrochemical technique shows isosbestic points clearly, indicating that the electrochemical reaction of (UO2)-O-VI(saldien) is only present. Using the absorbance change and the Nernstian equation, the electron stoichiometry in the reduction of (UO2)-O-VI(saldien) in DMSO was determined as 0.929. This quantity close to unity reveals a redox reaction, (UO2)-O-VI(saldien) + e(-) = [(UO2)-O-V(saldien)](-), i. e., (UO2)-O-VI(saldien) without unidentate ligands results in the stable U(V) complex, [(UO2)-O-V(saldien)](-), in DMSO. This U(V) species also shows the characteristic absorption bands of U(V) at 630, 700, 830, 1390, and 1890 nm as well as other U(V) complexes.
  • Masaru Kato, Toshiyuki Takayanagi, Takashi Fujihara, Akira Nagasawa
    INORGANICA CHIMICA ACTA 362 4 1199 - 1203 2009年03月 [査読有り][通常論文]
     
    Density functional theory (DFT) calculations have been performed for understanding the linkage isomerism of [Ru-II/III(NH3)(5)(dmso)](2+/3+) (dmso = dimethylsulfoxide) from a theoretical point of view. In particular, we focus on the interchange between O-bonded and S-bonded structures of the dmso ligand by oxidation/reduction. We have examined. five different exchange-correlation functionals (SVWN, BP86, mPWPW91, B3PW91, and B3LYP) in our DFT calculations and found that the relative stabilities of the O-bonded and S-bonded structures are largely dependent on the functional employed. From detailed analyses of atomic charge distributions, it has been found that the calculated atomic charges on the central metal ions are strongly correlated with the relative energies. We also studied the effect of solvation on the linkage isomerism using continuum solvation models. (C) 2008 Elsevier B. V. All rights reserved.
  • Masaru Kato, Miho Hayashi, Takashi Fujihara, Akira Nagasawa
    ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE 64 M684 - U621 2008年05月 [査読有り][通常論文]
     
    The absolute configuration of the octahedral fac-CoN3O3 title complex, [Co(C5H8NO2)(3)]center dot 3H(2)O, has been determined by single-crystal X- ray analysis. A three-dimensional network of hydrogen bonds is observed between the proline carboxylate groups and the three uncoordinated water molecules.
  • Masaru Kato, Takashi Fujihara, Daisaku Yano, Akira Nagasawa
    CRYSTENGCOMM 10 10 1460 - 1466 2008年 [査読有り][通常論文]
     
    Silver(I) coordination polymers formed by self-assembly of ambidentate ligands, 2-methylisothiazol-3(2H)-one (MI) and 5-chloro-2-methylisothiazol-3(2H)-one (CMI), have been characterized by single crystal X-ray analysis. The structure of the cation in [Ag-I(mu-O-mi)(2)] X (X = ClO4- (1); SbF6- (2)) is a one-dimensional chain while that in the nitrate salt, [Ag-2(I)(mu-O-mi)](NO3)(2) (3), is a three-dimensional network. A silver(I) complex with CMI, [Ag-I(mu-O-cmi)(2)] ClO4 (4), has also been synthesized and the cation has a one-dimensional chain structure. Although both MI and CMI have both O-and S-donor moieties, the oxygen atom dominantly coordinates to the silver(I) centre. The anion influence on the chain structure is attributed to the competition for the coordination ability between anions and MI, and the flexibility of the coordination sphere of d(10) silver(I) ion.
  • Masaru Kato, Takashi Fujihara, Daisaku Yano, Akira Nagasawa
    ACTA CRYSTALLOGRAPHICA SECTION E-CRYSTALLOGRAPHIC COMMUNICATIONS 63 O3097 - U2523 2007年07月 [査読有り][通常論文]
     
    The title molecule, C4H4ClNOS, contains an essentially planar five-membered ring. The C - C(= O) bond is slightly longer than expected. In the crystal structure, two-dimensional networks are formed through intermolecular C - Cl...O = C interactions [Cl...O = 2.9811 (19) angstrom].
  • Masaru Kato, Takashi Fujihara, Daisaku Yano, Akira Nagasawa
    Acta Crystallographica Section E: Structure Reports Online 63 7 o3097  2007年06月06日 [査読有り][通常論文]
     
    The title mol-ecule, C4H4ClNOS, contains an essentially planar five-membered ring. The C C(=O) bond is slightly longer than expected. In the crystal structure, two-dimensional networks are formed through inter-molecular C - Cl⋯O=C inter-actions [Cl⋯O = 2.9811 (19) Å]. © International Union of Crystallography 2007.
  • Masaru Kato, Takashi Fujihara, Daisaku Yano, Akira Nagasawa
    ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE 63 O1839 - O1841 2007年04月 [査読有り][通常論文]
     
    The title compound, C4H6ClNOS center dot H2O, has a planar five-membered ring, with a delocalized positive charge. A three-dimensional network is formed through intermolecular O-H center dot center dot center dot O and O-H center dot center dot center dot Cl hydrogen bonds between 3-hydroxy-2-methylisothiazolium cations and water molecules, and between water molecules and chloride anions.
  • T Fujihara, M Kato, A Nagasawa
    ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE 61 O1439 - O1440 2005年05月 [査読有り][通常論文]
     
    The crystallographic analysis of the title compound, C12H28N+• ClO4-, (I), shows that intermolecular C-H••• O interactions stabilize the crystal structure. The compound is isomorphous with tetra-n-propylammonium iodide, whose structure has been described by Yoshida et al. [ Acta Cryst. ( 1994). C50, 1758-1760].

書籍

その他活動・業績

受賞

  • 2020年11月 日本化学会北海道支部奨励賞
     触媒–電極接合界面の設計と高活性電極触媒開発 
    受賞者: 加藤優
  • 2018年02月 Symposium on Nanomaterials for Environmental Purification and Energy Conversion (SNEPEC) Best Poster Award
     Incorporation of multinuclear copper active sites into nitrogen-doped carbon for electrochemical oxygen reduction 
    受賞者: 加藤 優
  • 2017年10月 International Symposium on Novel Energy Nanomaterials, Catalysts and Surfaces for Future Earth (NENCS) –Material Research, Characterization and Imaging by in situ/Operando XAFS and X-ray Techniques– NENCS Poster Award (General)
     Efficient Electrochemical Oxygen Reduction Catalyzed at Multinuclear Copper Active Sites Incorporated in Nitrogen-Doped Carbon Nanosheets 
    受賞者: 加藤 優
  • 2016年05月 公益社団法人日本表面科学会 第35回表面科学学術講演会講演奨励賞(新進研究者部門)
     カーボン担持銅二核錯体からなる酸素還元電極触媒のin situ XAFS観察 
    受賞者: 加藤 優

共同研究・競争的資金等の研究課題

  • 電極支持生体膜反応場を用いたタンパク質間相互作用の理解とカスケード反応への展開
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 加藤 優
  • 電解をコアテクノロジーとした集積化可能なパーソナルグリッド(PG)の実現に関する調査研究
    国立研究開発法人科学技術振興機構:ムーンショット型研究開発事業 新たな目標検討のためのビジョン策定(ミレニア・プログラム)
    研究期間 : 2021年01月 -2021年06月 
    代表者 : 長澤 兼作, 才田隆広, 加藤優, 滝本大裕, 八木裕之, 山口清
  • 日本学術振興会:科学研究費助成事業 若手研究(B)
    研究期間 : 2016年04月 -2019年03月 
    代表者 : 加藤 優, 八木 一三, 當舎 武彦
     
    膜貫通型金属酵素の多くが高い触媒活性を示すことが知られているが,一般的に容易に失活することからそれらの電気化学活性評価および表面増強赤外吸収(SEIRA)分光計測の研究例は限られていた.本研究を通して,膜結合型金属酵素の一つである一酸化窒素還元酵素(NOR)を失活することなく電極表面に固定化する方法を確立することができ,更には,NOR電極の電位制御下でのSEIRA分光計測を実施することで,酵素反応機構に関する知見を得ることができた.本研究で用いた表面分光酵素電気化学は他の金属酵素へも適用可能であり,金属酵素の動作原理の解明や高活性な人工電極触媒開発における設計指針を与えてくれると期待している.
  • 酸化還元誘起結合異性錯体の設計、合成、および分子間光電子移動反応
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 2009年 -2010年 
    代表者 : 加藤 優
     
    ベンゾトリアゾール(Hbt)は配位可能な窒素原子を二つ有する両座配位子である.過去に酸化還元誘起結合異性を示すルテニウム錯体が合成されていて,Ru^の状態ではHbtが2位の窒素(N(2))で中心金属イオンに配位しているが,中心金属イオンを酸化してRu^の状態にするとHbtが3位の窒素(N(3))で配位することが知られている.そこで,Hbtを両座配位子とし,補助配位子として光受容性配位子である2,2':6',2''-terpyridine (tpy)や2,2'-bipyridine誘導体を有するルテニウム錯体[Ru^(Hbt) L (tpy)](CF_3SO_3)_2(Lは4,4'位をH,Me,OMe,tBu,Phで置換された2,2'-bipyridine誘導体)を合成し,溶液内酸化還元挙動をサイクリックボルタンメトリー測定により検討を行った.しかしながら酸化還元誘起結合異性に由来するようなピークを観測することはできず酸化還元誘起結合異性挙動が見られなかった.そこで,代替化合物として過去に我々が報告している酸化還元誘起結合異性を示す錯体[Ru(NH_3)_5(mi-S)]^(mi=2-methylisothiazol-3(2H)-One ; n=3 or 2),光増感剤ルテニウム錯体[Ru^(bpy)_3]Cl_2,そしてmethylviologen (MV)を用い,三元系分子間光電子移動反応による酸化還元結合異性を誘起するシステムの構築を目指した.その過程でRu^の状態miが硫黄で,Ru^では酸素で配位した錯体をそれぞれ合成単離し,単結晶X線構造解析によって構造を決定した。このように酸化還元結合異性体の単離例は極めて少なく,これは予期せぬ大きな成果であった.

教育活動情報

主要な担当授業

  • ナノ環境材料化学特論Ⅲ
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 固体表面構造、ナノ構造材料、自己組織化単分子層、電気化学、半導体電極、電極触媒 Surface structure of solid materials, Nanostructured materials, Self-assembled monolayer, Electrochemistry, Semiconductor electrode, and Electrocatalysis
  • 化学Ⅰ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 原子の構造、原子軌道、化学結合、混成軌道、物質の三態、電解質溶液


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