Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Ken Sakai Last modified date:2019.12.26

Professor / Inorganic and Analytical Chemistry / Department of Chemistry / Faculty of Sciences

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2. Yuto Sakaguchi, Arnau Call, Mihaela Cibian, Kosei Yamauchi, Ken Sakai, An earth-abundant system for light-driven CO2 reduction to CO using a pyridinophane iron catalyst, Chemical Communications, 10.1039/c9cc04191e, 55, 59, 8552-8555, 2019.01, Herein we report an earth-abundant photocatalytic system for CO2 reduction to CO based on an iron catalyst combined with a CuI photosensitizer. Under visible light irradiation CO is produced as the main product (TONCO = 565, TOFmaxCO = 114 h-1) with a high selectivity over H2 production (SelCO2 = 84%)..
3. Ryoichi Kuwano, Masashi Yokogi, Ken Sakai, Shigeyuki Masaoka, Takashi Miura, Sungyong Won, Room-Temperature Benzylic Alkylation of Benzylic Carbonates
Improvement of Palladium Catalyst and Mechanistic Study, Organic Process Research and Development, 10.1021/acs.oprd.9b00210, 23, 8, 1568-1579, 2019.08, The palladium catalyst for the nucleophilic substitution of benzyl carbonates was improved by using 1,1′-bis(diisopropylphosphino)ferrocene (DiPrPF) as the ligand. The [Pd(η3-C3H5)(cod)]BF4-DiPrPF catalyst allows the benzylic substitution with soft carbanions to proceed even at 30 °C, affording the desired products in high yields (up to 99% yield). Thermally unstable pyridylmethyl esters are employable as the electrophilic substrates for the benzylic alkylation with the improved catalyst. Furthermore, we investigated the mechanism of the catalytic benzylic alkylation by means of DiPrPF ligand. The palladium(0) complex bearing DiPrPF activates the benzylic C-O bond to form the (benzyl)palladium(II) intermediate at room temperature. The coordination mode of the benzyl ligand would be equilibrium between the η1- and η3-manner. The nucleophile would preferentially react with the η3-benzyl ligand to give the desired product..
4. Jia Wei Wang, Kosei Yamauchi, Hai Hua Huang, Jia Kai Sun, Zhi Mei Luo, Di Chang Zhong, Tong Bu Lu, Ken Sakai, A Molecular Cobalt Hydrogen Evolution Catalyst Showing High Activity and Outstanding Tolerance to CO and O2, Angewandte Chemie - International Edition, 10.1002/anie.201904578, 58, 32, 10923-10927, 2019.07, 一般的に触媒活性が低下する一酸化炭素/酸素雰囲気下においても、優れた水素生成触媒特性を示すコバルト錯体触媒を開発した。また、その耐久性発現因子の解明にも成功した。.
5. Alexander Rene Parent, Takashi Nakazono, Yuta Tsubonouchi, Natsuki Taira, Ken Sakai, Mechanisms of water oxidation using ruthenium, cobalt, copper, and iron molecular catalysts, Advances in Inorganic Chemistry, 10.1016/bs.adioch.2019.04.001, 197-240, 2019.01, This review focuses on the studies of molecular water oxidation catalysts based on ruthenium, cobalt, copper, and iron, with emphasis given to the works undertaken thus far by the authors' group in the last decade. A particular emphasis is given on our mechanistic studies of water oxidation, and the involvement of the chemical oxidants employed in the catalytic mechanism..
6. Keita Koshiba, Kosei Yamauchi, and Ken Sakai, Ligand-based PCET Reduction in a Heteroleptic Ni(bpy)(dithiolene) Electrocatalyst Giving Rise to Higher Metal Basicity Required for Hydrogen Evolution, CHEMELECTROCHEM, 2019.04, Proton abstraction leading to the formation of a hydride species required to evolve H2 largely relies on the basicity of d orbital of the metal responsible for this action. Here we report that a square‐planar NiII(bpy)(dcbdt) hydrogen evolution catalyst shows substantial acceleration in the proton abstraction rate due to the increased basicity at the filled Ni dz2 orbital after formation of [NiI(bpy−.)(dcbdt)]2− via consecutive two one‐electron reductions (bpy=2,2′‐bipyridine; dcbdt=4,5‐dicyanobenzene‐1,2‐dithiolate). The catalyst is likely to adopt the EECC′ mechanism in which the rate of the first protonation step is by far higher than that of the second step, even though an alternative path requiring another reduction (i. e., ECEC′) remains unexcluded. Our DFT calculations reveal that the first and second reductions are correlated with the electron injection into the metal‐ligand anti‐bonding and π*(bpy) orbitals, respectively, where the latter orbital shows non‐negligible hybridization with the nickel d orbital. In addition, a homoleptic catalyst [NiII(dcbdt)2]2− is shown to adopt the EC′EC mechanism with the rate‐determing step being a hydride forming step, consistent with the largely delocalized nature of the injected electron over the two dcbdt ligands (π*(dcbdt) orbital). This work demonstrates the importance of raising the basicity of the metal d orbital, relevant to promote the proton‐coupled electron transfer (PCET)..
7. Arnau Call, Mihaela Cibian, Keiya Yamamoto, Takashi Nakazono, Kosei Yamauchi, and Ken Sakai, Highly Efficient and Selective Photocatalytic CO2 Reduction to CO in Water by a Cobalt Porphyrin Molecular Catalyst, ACS Catalysis, 10.1021/acscatal.8b04975, 9, 4867-4874, 2019.04, The performance of a water-soluble cobalt porphyrin ([{meso-tetra(4-sulfonatophenyl)porphyrinato}cobalt(III)], CoTPPS) as a catalyst for the photoreduction of CO2 in fully aqueous media has been investigated under visible light irradiation using [Ru(bpy)3]2+ as a photosensitizer and ascorbate as a sacrificial electron donor. CO is selectively produced (>82%) with high efficiency (926 TONCO; TONCO = turnover number for CO). Upon optimization, selectivities of at least 91% are achieved. Efficiencies up to 4000 TONCO and 2400 h–1 TOFCO (TOFCO = turnover frequency for CO) are reached at low catalyst loadings, albeit with loss in selectivity. This work successfully demonstrates the ability of CoTPPS to perform highly efficient photoreduction of CO2 in water while retaining its high selectivity for CO formation..
8. Kohei Morita, Ken Sakai, and Hironobu Ozawa, A New Class of Molecular-Based Photoelectrochemical Cell for Solar Hydrogen Production Consisting of Two Mesoporous TiO2 Electrodes, ACS Publications, 10.1021/acsaem.8b01992, ACS Appl. Energy Mater., 2019, 2 (2), pp 987–992, 2019.01.
9. Keita Koshiba, Kosei Yamauchi, and Ken Sakai, Consecutive Ligand-based PCET Processes Affording a Doubly Reduced Nickel Pyrazinedithiolate which Transforms into a Metal Hydride Required to Evolve H2, Dalton Transaction, 10.1039/C8DT04497J, 2018.11, [URL], Our DFT results demonstrate that hydrogen evolution from water catalyzed by a nickel pyradinedithiolate (dcpdt) molecular hydrogen evolution catalyst [NiII(dcpdt)2]2− proceeds via the formation of a square-planar nickel(II) hydride intermediate which is given by unprecedented structural transformation of a doubly reduced triply protonated species [NiII(dcpdtH2)(dcpdtH)]−, afforded as a result of two consecutive ligand-based reductions of [NiII(dcpdt)(dcpdtH)]− through proton-coupled electron transfer (PCET) pathways.!divAbstract.
10. Yutaro Aimoto, Keita Koshiba, Kosei Yamauchi and Ken Sakai , "A family of molecular nickel hydrogen evolution catalysts providing tunable overpotentials using ligand-centered proton-coupled electron transfer paths", Chemical Communications, 10.1039/C8CC07467D, 2018.10, Two new nickel dithiolate derivatives have been examined for their electrocatalytic activity for hydrogen evolution reaction (HER) in attempts to clarify whether the overpotential for HER can be tuned upon varying the ligand-centered reduction potential that triggers HER by the catalysts. We demonstrate the validity of this approach to achieve desirable tunability in the overpotential for HER..
11. Keiya Yamamoto, @Arnau Call, Ken Sakai, Photocatalytic H2 Evolution using a Ru Chromophore tethered to Six Viologen Acceptors, CHEMISTRY A European Journal, 10.1002, chem.201803662, 2018.08, [URL], A new photo‐charge‐separator (PCS) consisting of a Ru(bpy)32+ (bpy: 2,2'‐bipyridine) chromophore and six viologen (MV2+) acceptors, [Ru(bpyMV2)3]14+, is synthesised and its application in photocatalytic H2 evolution is reported. The present PCS possesses shorter linkers in connecting a Ru chromophore and MV2+ acceptors in comparison with our previous PCSs (Inorg. Chem. Front., 2016, 3, 671‐680) and shows consecutive photo‐driven electron transfer in the presence of a sacrificial electron donor (EDTA), leading to multi‐electron storage over the PCS. This behavior can also be coupled with catalytic H2 evolution by the presence of a colloidal Pt catalyst. More importantly, the present PCS exhibits much higher durability during the photolysis, which is attributed to the higher rate in catalytic process. The high durability is also attributed to its bulky framework preventing undesirable side reactions..
12. Anas Lataifeh, Heinz Bernhard Kraatz, Firas F. Awwadi, Mohammed A. Zaitoun, Ken Sakai, Platinum(II)-glutamic acid dendrimer conjugates
Synthesis, characterization, DFT calculation, conformational analysis and catalytic properties, Inorganica Chimica Acta, 10.1016/j.ica.2017.12.022, 473, 245-254, 2018.03, A series of platinum(II)-L-glutamic acid dendrimer conjugates having the formula PtCl2(5,5′-Gn(OR)-2,2′-bipyridine); Gn (n = 0, 1, 2), have been synthesized by various amide bond formation methods. The dendrimer complexes were terminated as carboxylic acid (R = H) or methyloxy ester (R = Me). The complexes were characterized by mass spectrometry, elemental analysis, UV-vis, FTIR, 1H-, 13C NMR, 1H-TOCSY, HSQC. The G1(OH) complex aggregate in solution and solid state, giving rise to a rigid conformation for the glutmaic acid side chain. The G2(OH) exists in the “monomeric” form with several conformations for the glutamic acid side chains. Complexes terminated with carboxyl group (R = H) were active catalyst toward hydrogen gas (H2) production by photo-induced splitting of water. The turnover frequency (TOF) for the G1(OH) complex is 14.7 × 1015 s−1, and it exhibits a ∼ 2-fold enhancement in H2 production compared to the unmodified parent complex G0(OH) (TOF = 7×1015 s−1). While G2(OH) complex displayed a lower hydrogen activity (TOF = 3.8 × 1015 s−1) compared to G0(OH). The platinum-glutamic acid dendrimer conjugates showed a correlation between H2 evolution activity and their ability to form aggregates, which driven by the steric hindrance of the peptide residues in the vicinity of Pt-center..
13. Tomohiro Watanabe, Hajime Shibata, Makoto Ebine, Hiroshi Tsuchikawa, Nobuaki Matsumori, Michio Murata, Manabu Yoshida, Masaaki Morisawa, Shu Lin, Kosei Yamauchi, Ken Sakai, and Tohru Oishi , Synthesis and Complete Structure Determination of a Sperm-Activating and -Attracting Factor Isolated from the Ascidian Ascidia sydneiensis, JOURNAL OF NATURAL PRODUCTS, 10.1021/acs.jnatprod.7b01052, J. Nat. Prod., 2018, 81 (4), pp 985–997, 2018.03,
14. Anas Lataifeh, Heinz-Bernhard Kraatz, Firas F. Awwadi, Mohammed A. Zaitoun, Ken Sakai, Platinum(II)-glutamic acid dendrimer conjugates: Synthesis, characterization, DFT calculation, conformational analysis and catalytic properties, Inorganica Chimica Acta, 10.1016/j.ica.2017.12.022, 2018.02.
15. Yutaro Tsuji, Keiya Yamamoto, Kosei Yamauchi, Ken Sakai, Near-Infrared-Light-Driven Hydrogen Evolution from Water using a Polypyridyl Triruthenium Photosensitizer, Angewandte Chemie - International Edition, 2017.11, ルテニウム三核の色素増感剤を利用することにより近赤外線領域の光を励起光として光化学的水素生成反応を駆動することに成功した。錯体の還元能が共存イオン種とのイオン会合体生成平衡によって精密制御可能であることも明らかにした。.
16. Kohei Morita, Kohei Takijiri, Ken Sakai, Hironobu Ozawa, A Platinum Porphyrin Modified TiO2 Electrode for Photoelectrochemical Hydrogen Production from Neutral Water Driven by the Conduction Band Edge Potential of TiO2, Dalton Transactions, 10.1039/C7DT03710D, 46, 15181-15185, 2017.10.
17. Shota Tanaka, Takashi Nakazono, Kosei Yamauchi, Ken Sakai, Photochemical H2 Evolution Catalyzed by Porphyrin-based Cubic Cages Singly and Doubly Encapsulating PtCl2(4,4’-dimethyl-2,2’-bipyridine), Chemistry Letters, 46, 1573, 2017.08.
18. Yan Suffren, Masayuki Kobayashi, Jeffrey S. Ovens, Alexandre Rodrigue-Witchel, Caroline Genre, Ken Sakai, Christian Reber, Daniel B. Leznoff, [Pt(SCN)4]2–-Based Coordination Polymers and Supramolecular Squares
Intermolecular Pt···H–C Interactions Probed by Luminescence Spectroscopy at Variable Pressure, European Journal of Inorganic Chemistry, 10.1002/ejic.201700514, 2017, 22, 2864, 2017.06.
19. Yan Suffren, Masayuki Kobayashi, Jeffrey S. Ovens, Alexandre Rodrigue-Witchel, Caroline Genre, Ken Sakai, Christian Reber, Daniel B. Leznoff, [Pt(SCN)4]2–-Based Coordination Polymers and Supramolecular Squares
Intermolecular Pt···H–C Interactions Probed by Luminescence Spectroscopy at Variable Pressure, European Journal of Inorganic Chemistry, 10.1002/ejic.201700149, 2017, 22, 2865-2875, 2017.06, The structures of four types of supramolecular systems containing [Pt(SCN)4]2– molecular units have been characterized. [Mn(bipy)2Pt(SCN)4]2·2MeOH (1) and [Zn(bipy)2Pt(SCN)4]2·2MeOH (2) show cis-thiocyanato ligands bridging the PtII and MnII or ZnII ions, leading to a molecular square motif. [Zn(bipy)2Pt(SCN)4]2 (3) presents chains where trans-thiocyanato ligands bridge the ZnII and PtII ions. For 1–3, free thiocyanato ligands are coordinated to the PtII centers to complete the square-planar coordination. [Pb(bipy)2Pt(SCN)4]2 (4) reveals a two-dimensional sheet structure where all SCN ligands bridge the PbII and PtII ions. [Pb(terpy)Pt(SCN)4]2 (5) is similar to 3, with two bridging trans-SCN ligands and two that are coordinated only to the PtII centers. For all compounds, d–d luminescence is observed with band maxima at approximately 14600 cm–1 (690 nm). Spectra show characteristic shifts with pressure, indicative of either intramolecular or intermolecular effects, depending on the sign of the shift. The pressure-dependent shifts for 1–5 show rich variations. A well-documented shift to higher energy due to metal–ligand bond compression is observed for 5 and can be used as a basis for a comparison. Compounds 1–4 show a shift of Emax to lower energy with pressures below 10 kbar. A change in sign for the shift of Emax occurs at 20, 12, and 10 kbar for 1, 2, and 3, respectively. For 4, only a shift to lower energy is observed. Competing intra- and intermolecular effects lead to these variations..
20. Masayuki Miyaji, Kyoji Kitamoto, Hironobu Ozawa, Ken Sakai, Synthesis and Characterization of a RuPt-Based Photo-Hydrogen-Evolving Molecular Device Tethered to a Single Viologen Acceptor, European Journal of Inorganic Chemistry, 10.1002/ejic.201601346, 2017, 9, 1237-1244, 2017.03.
21. Keita Koshiba, Kosei Yamauchi, Ken Sakai, A Nickel Dithiolate Water Reduction Catalyst Providing Ligand-Based Proton-Coupled Electron-Transfer Pathways, Angewandte Chemie - International Edition, 10.1002/anie.201700927, 56, 15, 4247-4251, 2017.03.
22. Kohei Takijiri, Kohei Morita, Takashi Nakazono, Ken Sakai, Hironobu Ozawa, Highly stable chemisorption of dyes with pyridyl anchors over TiO2
Application in dye-sensitized photoelectrochemical water reduction in aqueous media, Chemical Communications, 10.1039/c6cc10321a, 53, 21, 3042-3045, 2017.02.
23. Kohei Morita, Kohei Takijiri, Ken Sakai, Hironobu Ozawa, A platinum porphyrin modified TiO2 electrode for photoelectrochemical hydrogen production from neutral water driven by the conduction band edge potential of TiO2, Dalton Transactions, 10.1039/c7dt03710d, 46, 44, 15181-15185, 2017.01, The onset potential for H2 production from neutral water (pH 7) catalyzed by a platinum(ii) porphyrin (PtP-py) modified TiO2 electrode positions very close to the standard water reduction potential (less than 50 mV). H2 production is driven by the conduction band edge potential of TiO2 at the PtP-py-modified TiO2 cathode..
24. Roman Goy, Luca Bertini, Tobias Rudolph, Shu Lin, Martin Schulz, Giuseppe Zampella, Benjamin Dietzek, Felix H. Schacher, Luca De Gioia, Ken Sakai, Wolfgang Weigand, Photocatalytic Hydrogen Evolution Driven by [FeFe] Hydrogenase Models Tethered to Fluorene and Silafluorene Sensitizers, Chemistry - A European Journal, 10.1002/chem.201603140, 23, 2, 334-345, 2017.01, It is successfully shown that photocatalytic proton reduction to dihydrogen in the presence of a sacrificial electron donor, such as trimethylamine (TEA) and ascorbate, can be driven by compact sensitizer–catalyst dyads, that is, dithiolate-bridged [FeFe] hydrogenase models tethered to organic sensitizers, such as fluorenes and silafluorenes (1 a–4 a). The sensitizer–catalyst dyads 1 a–4 a show remarkable and promising catalytic activities as well as enhanced stabilities during photocatalysis performed under UV-light irradiation. The photocatalysis was carried out both in non-aqueous and aqueous media. The latter experiments were performed by solubilizing the photocatalysts within micelles formed by either sodium dodecyl sulfate (SDS) or cetyltrimethylammonium bromide (CTAB). In this study a turnover number of 539 (7 h) is achieved under optimized conditions, which corresponds to an exceptionally high turnover frequency of 77 h−1. Theoretical investigations as well as emission decay experiments were performed to understand the observed phenomena together with the mechanisms of photocatalytic H2 generation..
25. Shota Tanaka, Takashi Nakazono, Kosei Yamauchi, Ken Sakai, Photochemical H2 evolution catalyzed by porphyrin-based cubic cages singly and doubly encapsulating PtCl2 (4,4'-dimethyl-2,2'-bipyridine), Chemistry Letters, 10.1246/cl.170692, 46, 10, 1573-1575, 2017, A porphyrin-based cubic cage (Cube) was reacted with a Pt(II)-based molecular H2-evolving catalyst, PtCl2 (dmbpy) (PtDmb; dmbpy: 4,4'-dimethyl-2,2'-bipyridine), to give Cubes incorporated with one or two equivalents of PtDmb, i.e., Cube(PtDmb) and Cube(PtDmb) 2, which was confirmed by ESI-TOF MS spectroscopy. A photochemical H2-evolving system consisting of EDTA (sacrificial electron donor), [Ru(bpy)3]2+ (photosensitizer), and methylviologen (electron relay) was used to demonstrate that the catalyst encapsulated can also serve as an effective H2-evolving catalyst..
26. Roman Goy, Luca Bertini, Tobias Rudolph, Shu Lin, Martin Schulz, Guiseppe Zampella, Benjamin Dietzek, Felix H. Schacher, Luca De Gioia, 酒井 健, Wolfgang Weigand, Photocatalytic Hydrogen Evolution Driven by [FeFe] Hydrogenase Models Tethered to Fluorene and Silafluorene Sensitizers, Chem. Eur. J., 10.1002/chem.201603140, 2016.12.
27. Gary W. Brudvig, Joost N. H. Reek, Ken Sakai, Leone Spiccia, and Licheng Sun, Catalytic Systems for Water Splitting, ChemPlusChem, 10.1002/cplu.201600436 , 81, 10, 1017-1019, 2016.10.
28. Gary W. Brudvig, Joost N H Reek, Ken Sakai, Leone Spiccia, Licheng Sun, Catalytic Systems for Water Splitting, ChemPlusChem, 10.1002/cplu.201600436, 81, 10, 1017-1019, 2016.10.
29. Ryota Terao, Takashi Nakazono, Alexander Rene Parent, Ken Sakai, Photochemical Water Oxidation Catalyzed by a Water-Soluble Copper Phthalocyanine Complex, ChemPlusChem, 10.1002/cplu.201600263, 81, 10, 1064-1067, 2016.10, Copper tetrasulfonatophthalocyanine (CuPcTS) is reported to serve as a catalyst for photochemical water oxidation via a radical coupling mechanism. Chloride greatly inhibits the water oxidation rate as a result of axial chloride binding to CuPcTS, preventing formation of the Cu oxyl or hydroxyl intermediate required for O−O bond formation..
30. Remko J. Detz, Ken Sakai, Leone Spiccia, Gary W. Brudvig, Licheng Sun, Joost N H Reek, Towards a Bioinspired-Systems Approach for Solar Fuel Devices, ChemPlusChem, 10.1002/cplu.201600446, 81, 10, 1024-1027, 2016.10.
31. Remko J. Detz, Leone Spiccia, Gary W. Brudvig, Licheng Sun, Joost N. H. Reek, 酒井 健, Towards a Bioinspired-Systems Approach for Solar Fuel Devices, ChemPlusChem, 10.1002/cplu.201600446, 81, 10, 1024-1027, 2016.09.
32. Ryota Terao, Takashi Nakazono, Alexander Rene Parent, 酒井 健, Photochemical Water Oxidation Catalysed by a Water-Soluble Copper Phthalocyanine, ChemPlusChem, 10.1002/cplu.201600263, 81, 1064-1067, 2016.07.
33. Takashi Nakazono, 酒井 健, Improving the robustness of cobalt porphyrin water oxidation catalysts by chlorination of aryl groups, Dalton Transactions, 10.1039/C6DT02535H, 45, 12649-12652, 2016.07.
34. Christopher H. Hendon, Aron Walsh, Norinobu Akiyama, Yosuke Konno, Takashi Kajiwara, Tasuku Ito, Hiroshi Kitagawa, Ken Sakai, One-dimensional Magnus-type platinum double salts, Nature Communications, 10.1038/ncomms11950, 7, 2016.06, Interest in platinum-chain complexes arose from their unusual oxidation states and physical properties. Despite their compositional diversity, isolation of crystalline chains has remained challenging. Here we report a simple crystallization technique that yields a series of dimer-based 1D platinum chains. The colour of the Pt2+ compounds can be switched between yellow, orange and blue. Spontaneous oxidation in air is used to form black Pt 2.33+ needles. The loss of one electron per double salt results in a metallic dz2 state, as supported by quantum chemical calculations, and displays conductivity of 11 S cm-1 at room temperature. This behaviour may open up a new avenue for controllable platinum chemistry..
35. Lin Shu, Kyoji Kitamoto, 小澤 弘宜, 酒井 健, Improved Photocatalytic Hydrogen Evolution Driven by Chloro(terpyridine)platinum(II) Derivatives Tethered to a Single Pendant Viologen Acceptor, Dalton Tranactions, 10.1039/C6DT01456A , 2016.05.
36. Yuta Tsubonouchi, Lin Shu, Alexander Rene Parent, Gary Brudvig, 酒井 健, Light-induced Water Oxidation Catalyzed by an Oxido-bridged Triruthenium Complex with a Ru-O-Ru-O-Ru Motif, Chemical Communications, 10.1039/C6CC02816K, 2016.05.
37. Christopher H. Hendon, Aron Walsh, Norinobu Akiyama, Yosuke Konno, Takashi Kajiwara, Tasuku Ito, Hiroshi Kitagawa, 酒井 健, One-dimensional Magnus-type platinum double salts, Nature Communications , 10.1038/ncomms11950, 2016.05, 金属的一次元伝導性を示す混合原子価白金一次元錯体の結晶構造と伝導物性について明らかにすると同時に、その一次元電子系の電子状態計算を行い、明確な現象論を提案することに成功した。.
38. Kyoji Kitamoto, Makoto Ogawa, Gopalakrishnan Ajayakumar, Shigeyuki Masaoka, Heinz Bernhard Kraatz, Ken Sakai, Molecular photo-charge-separators enabling single-pigment-driven multi-electron transfer and storage leading to H2 evolution from water, Inorganic Chemistry Frontiers, 10.1039/c5qi00150a, 3, 5, 671-680, 2016.05, Single-chromophore-driven single-electron-pumping processes leading to multi-electron transfer and storage are effectively promoted in natural photosynthesis, generating photocurrent at the molecular level. Moreover, these single-electron-pumping events are converted into double-electron-pumping events by releasing multiple plastoquinol molecules without releasing reactive semiquinone radicals, thereby enabling storage of two-electron-reduced molecules within the lipid bilayer constructing the thylakoid membrane. Here we report new unimolecular architectures that enable these highly sophisticated light-driven multi-electron transfer and storage processes. The photo-charge-separators (PCSs) reported herein possess a single Ru(bpy)32+ fragment with each bpy derivatized with four dicationic viologen acceptors, abbreviated as [RuII(bpy)32+-(MV2+)12]26+ (MV2+ is a viologen unit). These highly positively charged PCSs form stable ion pairs with anionic electron donors, enabling consecutive multi-electron transfer processes from the donors to the pendant viologen acceptors. The multiple transferred electrons are collected over twelve pendant viologen acceptors, leading to storage of 7-8 electrons per molecule. The resulting organic radicals show a strong preference to form diamagnetic π-dimers, which suppress reactive radical formation. These reducing equivalents can then be efficiently consumed in catalytic H2 evolution from water in the presence of a colloidal platinum catalyst..
39. Kyoji Kitamoto, Makoto Ogawa, Gopalakrishnan Ajayakumar, Shigeyuki Masaoka, Heinz-Bernhard Kraatz, 酒井 健, Molecular photo-charge-separators enabling single-pigment-driven multi-electron transfer and storage leading to H2 evolution from water, Inorganic Chemistry Frontiers, 10.1039/C5QI00150A , 2016.02.
40. Kyoji Kitamoto, Ken Sakai, Photochemical H2 evolution from water catalyzed by a dichloro(diphenylbipyridine)platinum(ii) derivative tethered to multiple viologen acceptors, Chemical Communications, 10.1039/c5cc08044d, 52, 7, 1385-1388, 2016.01, A new single-component photocatalyst for the reduction of water to H2, a dichloro(dpbpy)platinum(ii) derivative (dpbpy = 4,4′-diphenyl-2,2′-bipyridine) tethered to four pendant viologen acceptors (1), is shown to exhibit twice higher photocatalytic efficiency than the previously reported dichloro(bpy)-platinum(ii) analog (2; bpy = 2,2′-bipyridine), consistent with the higher absorptivity of 1 at the metal-to-ligand charge transfer (1MLCT) band due to the larger π-conjugation in dpbpy relative to bpy..
41. Shu Lin, Kyoji Kitamoto, Hironobu Ozawa, Ken Sakai, Improved photocatalytic hydrogen evolution driven by chloro(terpyridine)platinum(II) derivatives tethered to a single pendant viologen acceptor, Dalton Transactions, 10.1039/c6dt01456a, 45, 26, 10643-10654, 2016, Three chloro(4′-(N-methylpyridinium)-2,2′:6′,2′′-terpyridine)platinum(ii) (abbreviated as PtL2+) derivatives tethered to a single alkyl viologen unit (-(CH2)n-CH2-N+C5H4-C5H4N+-CH3; abbreviated as -Cn-MV2+, where n = 1, 3, and 4), i.e., PtL2+-Cn-MV2+, have been synthesized and investigated in detail. It is shown that the turnover number (TON) for the photocatalytic H2 evolution from water in the presence of a sacrificial electron donor EDTA (ethylenediaminetetraacetic acid disodium salt) is dramatically improved by the attachment of a single alkyl MV2+ unit (TON = 21.5-25.2, 12 h). Spectrophotometric studies reveal that the photoirradiation of PtL2+-Cn-MV2+ in the presence of EDTA initially leads to the formation of a 1-electron-reduced species, and then to a 2-electron-reduced species, where reductive quenching of a photoexcited species is a major path to the reduced photoproduct in each step. Electrochemical studies show that two consecutive 1-electron reductions at the PtL2+ unit are nearly overlapped with the corresponding reductions at the MV2+ unit. The 1-electron-reduced species can be thus expressed as either PtL+-Cn-MV2+ or PtL2+-Cn-MV+, while the 2-electron-reduced one as PtL+-Cn-MV+. Moreover, the latter products behave as stacked species involving three types of π-dimer sites, (PtL+)2, (MV+)2, and (PtL+)(MV+), and do not drive thermal H2 evolution according to the reaction: PtL+-Cn-MV+ + 2H+ → PtL2+-Cn-MV2+ + H2. The H2 evolution from water photocatalyzed by PtL2+-Cn-MV2+ has been found to occur via formation of 3-electron-reduced species; PtL+-Cn-MV+ + EDTA + hν → PtL0-Cn-MV+ (or PtL+-Cn-MV0) + EDTA(ox), and PtL0-Cn-MV+ (or PtL+-Cn-MV0) + 2H+ → PtL+-Cn-MV2+ (or PtL2+-Cn-MV+) + H2..
42. Takashi Nakazono, Ken Sakai, Improving the robustness of cobalt porphyrin water oxidation catalysts by chlorination of aryl groups, Dalton Transactions, 10.1039/c6dt02535h, 45, 32, 12649-12652, 2016, The water oxidation (WO) activity of a chlorinated cobalt tetraphenylporphyrin (CoClPS), possessing Cl atoms on the 2,6-positions of the aryl groups, shows higher resistance to attack by singlet oxygen, in situ generated during photochemical WO using Ru(bpy)3 2+ and S2O8 2- with the turnover frequency (TOF) and turnover number (TON) reaching 1.7 s-1 and 836, respectively..
43. Yuta Tsubonouchi, Shu Lin, Alexander R. Parent, Gary W. Brudvig, Ken Sakai, Light-induced water oxidation catalyzed by an oxido-bridged triruthenium complex with a Ru-O-Ru-O-Ru motif, Chemical Communications, 10.1039/c6cc02816k, 52, 51, 8018-8021, 2016, A μ-oxido-bridged triruthenium complex (RuT2+), formed by air-oxidation of a previously reported monoruthenium water oxidation catalyst (WOC), serves as an efficient photochemical WOC with the turnover frequency (TOF) and turnover number (TON) 0.90 s-1 and 610, respectively. The crystal structures of RuT2+ and its one-electron oxidized RuT3+ are also reported..
44. Kyoji Kitamoto, 酒井 健, Photochemical H2 Evolution from Water Catalyzed by Dichloro(diphenylbipyridine)platinum(II) Derivative Tethered to Multiple Viologen Acceptors, Chem. Commun., 10.1039/C5CC08044D , 52, 1385-1388, 2015.11.
45. Keiya Yamamoto, Kyoji Kitamoto, 山内 幸正, 酒井 健, Pt(II)-Catalyzed Photosynthesis for H2 Evolution Cycling Between Singly and Triply Reduced Species, Chem. Commun., 10.1039/C5CC03558A , 51, 14516-14159, 2015.08.
46. Masaki Yoshida, Mio Kondo, Sena Torii, 酒井 健, Shigeyuki Masaoka, Oxygen Evolution Catalysed by a Mononuclear Ruthenium Complex bearing Pendant -SO3- Groups, Angew. Chem. Int. Ed., 10.1002/anie.201503365, 54, 27, 7981-7984, 2015.05.
47. Takashi Nakazono, Alexander Rene Parent, 酒井 健, Improving Singlet Oxygen Resistance during Photochemical Water Oxidation by Cobalt Porphyrin Catalysts, Chem. Eur. J., 21, 6723-6726, 2015.03.
48. 山内 幸正, 酒井 健, A tricarboxylated PtCl(terpyridine) derivative exhibiting pH-dependent photocatalytic activity for H2 evolution from water, Dalton Trans., 10.1039/C5DT00425J , 2015.03.
49. Masaki Yoshida, Mio Kondo, Toshikazu Nakamura, 酒井 健, Shigeyuki Masaoka, Three Distinct Redox States of an Oxo-Bridged Dinuclear Ruthenium Complex, Angew. Chem., Int. Ed, 2014.09.
50. Alexander Rene Parent, 酒井 健, Progress in Base-Metal Water Oxidation Catalysis, ChemSusChem, 7, 2070-2080, 2014.07.
51. Alexander Rene Parent, Takashi Nakazono, Lin Shu, Satoshi Utsunomiya, 酒井 健, Mechanism of Water Oxidation by Non-Heme Iron Catalysts when Driven with Sodium Periodate, Dalton Trans, 2014.07.
52. Ken Kawano, 山内 幸正, 酒井 健, A Cobalt-NHC Complex as an Improved Catalyst for Photochemical Hydrogen Evolution from Water, Chem. Commun, 2014.07.
53. Takumi Nagashima, Takuya Nakabayashi, Takashi Suzuki, Katsuhiko Kanaizuka, Hiroaki Ozawa, Yu-Wu Zhong, Shigeyuki Masaoka, 酒井 健, Masa-aki Haga, Tuning of Metal-Metal Interactions in Mixed-Valence States of Cyclometalated Dinuclear Ruthenium and Osmium Complexes Bearing Tetrapyridylpyrazine or -benzene, Organometallics, 2014.05.
54. Kyoji Kitamoto, 酒井 健, Pigment-Acceptor-Catalyst Triads for Photochemical Hydrogen Evolution, Angew. Chem., Int. Ed., , 2014.03, 水からの光化学的な水素生成反応は、水素エネルギー社会を実現するにあたって極めて重要な研究領域である。本成果では、以前我々のグループが報告した、天然の光合成を模倣したZスキーム型光水素発生デバイスの活性を、電子一時貯蔵サイトを導入させることで大幅に向上させることに成功した。本研究により得られた分子設計の指針は、様々な触媒反応系に応用可能であり大きな波及効果を示すと期待される。.
55. Hoda A. El-Ghamry, Shigeyuki Masaoka, 酒井 健, Hydrogen-bonded frameworks of propylenediamine-N,N'-diacetic acid Pt(II) complexes, synthesis, structural characterization and antitumor activity, J. Coord. Chem, 2014.03.
56. K. El-Baradie, R. El-Sharkawy, H. El-Ghamry, 酒井 健, Synthesis and characterization of Cu(II), Co(II) and Ni(II) complexes of a number of sulfadrug azodyes and their application for wastewater treatment, Spectrochim. Acta, Part A, 2014.03.
57. Chettiyam Veettil Suneesh, Bijitha Balan, Hironobu Ozawa, Yuki Nakamura, Tetsuro Katayama, Masayasu Muramatsu, Yutaka Nagasawa, Hiroshi Miyasaka, 酒井 健, Mechanistic Studies of Photoinduced Intramolecular and Intermolecular Electron Transfer Processes in RuPt-centred Photo-hydrogen-evolving Molecular Devices, Phys. Chem. Chem. Phys, 10.1039/C3CP54630F , 4, 16, 1607-1616, 2013.11.
58. Dong Ryeol Whang, 酒井 健, Soo Young Park, Highly Efficient Photocatalytic Water Reduction with Robust Iridium(III) Photosensitizers Containing Arylsilyl Substituents, Angew. Chem. Int. Ed., 10.1002/anie.201305684, 2013.09.
59. Takashi Nakazono, Alexander Rene Parent, Ken Sakai, Cobalt Porphyrins as Homogeneous Catalysts for Water Oxidation, Chem. Commun., 10.1039/C3CC43031F, 49, 6325-6327, 2013.05, 水からの光化学的な酸素発生反応は、水を電子源とした水素生成反応や二酸化炭素還元反応に応用することが出来るため、非常に活発に行われている。本研究では、種々のコバルトポルフィリン錯体が非常に高い光酸素発生触媒活性を示すことを明らかにした。さらに、触媒反応の触媒濃度依存性から、反応の律速段階は、2分子会合過程であることが判明した。また、触媒反応の分解過程についても明らかにした。.
60. Masayuki Kobayashi, Didier Savard, Andrew R. Geisheimer, 酒井 健, Daniel B. Leznoff, Heterobimetallic Coordination Polymers Based on the [Pt(SCN)4]2– and [Pt(SeCN)4]2– Building Blocks, Inorg. Chem., 10.1021/ic302360b, 2013.04.
61. H. A. EL-Ghamry,* K. Sakai, S. Masaoka, K. Y. El-Baradie, R. M. Issa , Preparation, Characterization, Biological Activity and 3D Molecular Modeling of Mn(II), Co(II), Ni(II), Cu(II), Pd(II) and Ru(III) Complexes of Some Sulfadrug Schiff Bases, Chinese Journal of Chemistry, 10.1002/cjoc.201280024, 30, 4, 881–890, 2012.04.
62. Keita Kuroiwa, Masaki Yoshida, Shigeyuki Masaoka, Kenji Kaneko, Ken Sakai, and Nobuo Kimizuka, Self-assembly of Tubular Microstructures from Mixed-valence Metal Complexes and their Reversible Transformation via External Stimuli, Angew. Chem. Int. Ed., 10.1002/anie.201105080, 51, 656-659, 2011.12.
63. Ayano Kimoto, Kosei Yamauchi, Masaki Yoshida, Shigeyuki Masaoka, and Ken Sakai, Kinetics and DFT Studies on Water Oxidation by Ce4+ Catalyzed by [Ru(terpy)(bpy)(OH2)]2+, Chem. Commun., 10.1039/C1CC15109F, 48, 239-241, 2011.11, 酒井グループでは以前ルテニウム単核錯体が、優れた酸素発生触媒であることを見出した。本論文では、この酸素発生反応のメカニズムを解明するため、触媒として用いているルテニウム錯体の水溶液と水の酸化剤である硝酸セリウム(IV)アンモニウムの水溶液を高速で混合し、紫外可視吸収スペクトルの時間変化を追跡した。この吸収スペクトルを解析することにより、5つの中間体が存在することが明らかになった。また、密度汎関数法で得られた結果と比較検討することにより、酸素発生に関与している活性種、並びに触媒反応機構を見出すことができた。.
64. Kosei Yamauchi, Shigeyuki Masaoka, and Ken Sakai, Stability of Pt(II)-Based H2-Evolving Catalysts against H2 in Aqueous Solution, Dalton Trans., 10.1039/C1DT11217A , 40, 12447-12449, 2011.10.
65. Gopalakrishnan Ajayakumar, Masayuki Kobayashi, Shigeyuki Masaoka, and Ken Sakai, Light-Induced Charge Separation and Photocatalytic Hydrogen Evolution from Water using RuIIPtII-Based Molecular Devices: Effects of Introducing Additional Donor and/or Acceptor Sites, Dalton Trans., 10.1039/C0DT01673J., 2011.02.
66. Masanari Hirahara, Shigeyuki Masaoka, and Ken Sakai, Syntheses, Characterization, and Photochemical Properties of Amidate-Bridged Pt(bpy) Dimers Tethered to Ru(bpy)32+ Derivatives, Dalton Trans., DOI:10.1039/C0DT01548B, 2011.02.
67. Masayuki Kobayashi, Shigeyuki Masaoka, and Ken Sakai, Syntheses, Characterization, and Photo-Hydrogen-Evolving Properties of Tris(2,2'-bipyridine)ruthenium(II) Derivatives Tethered to an H2-Evolving (2-phenylpyridinato)platinum(II) Unit, Molecules, 15, 4908-4923, 2010, 15, 4908-4923.
, 2010.07.
68. Shigeyuki Masaoka, Yuichiro Mukawa, and Ken Sakai, Frontier Orbital Engineering of Photo-Hydrogen-Evolving Molecular Devices: a Clear Relationship Between the H2-Evolving Activity and the Energy Level of the LUMO, Dalton Trans., 39, 5868-5876, 2010, 39, 5868-5876., 2010.04, 本論文で報告した研究では、光水素発生デバイスの電子移動過程を明らかにするため、ルテニウム錯体部位及び白金錯体部位を共有結合でリンクした新規光水素発生デバイスの開発を行った。さらに、それらの光水素発生デバイスの活性及び光電子移動過程の評価を行った。その結果、白金側に配位したπ共役系配位子の還元電位の精密制御により、分子内電子移動の駆動力を自在に制御できることが判明した。また、見出した法則は、広く適用することができる重要なものであることが分かった。.
69. Makoto Ogawa, Bijitha Balan, Gopalakrishnan Ajayakumar, Shigeyuki Masaoka, Heinz-Bernhard Kraatz, Masayasu Muramatsu, Syoji Ito, Yutaka Nagasawa, Hiroshi Miyasaka and Ken Sakai, Photoinduced Electron Transfer in Tris(2,2´-bipyridine)ruthenium(II)-Viologen Dyads with Peptide Backbones Leading to Long-Lived Charge Separation and Hydrogen Evolution
, Dalton Trans., in press, 2010.03.
70. Hoda El-Ghamry, Raafat Issa, Kamal El-Baradie, Shigeyuki Masaoka and Ken Sakai, Dibromido(2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene)cobalt(III) bromide, Acta Cryst., E65, m1378-m1379, 2009.12.
71. Masaki Yoshida, Shigeyuki Masaoka and Ken Sakai, Oxygen Evolution from Water Catalyzed by Mononuclear Ruthenium Complexes with a Triazamacrocyclic Ligand in a Facial Fashion, Chem. Lett., 2009, 38, 702-703, 2009.07.
72. Hisashi Itoh, Eiji Yamamoto, Shigeyuki Masaoka, Ken Sakai and Makoto Tokunaga, Kinetic Resolution of P-Chirogenic Compounds by Pd-catalyzed Alcoholysis of Vinyl Ethers, Adv. Synth. Cat., 2009, 351, 1796-1800, 2009.07.
73. Reiko Okazaki, Shigeyuki Masaoka and Ken Sakai, Photo-Hydrogen-Evolving Activity of Chloro(terpyridine)platinum(II): a Single-Component Molecular Photocatalyst, Dalton Trans., 2009, 6127-6133, 2009.06.
74. Kosei Yamauchi, Shigeyuki Masaoka and Ken Sakai, Evidence for the Pt(II)-Based Molecular Catalysis in Thermal Reduction of Water into Molecular Hydrogen, J. Am. Chem. Soc., 2009, 131, 8404-8406, 2009.06.
75. T. Yamaguchi, S. Masaoka and K. Sakai, Hydrogen Production from Water Catalyzed by an Air-stable Di-iron Complex with a Bio-relevant Fe2(μ-S)2 Core, Chem. Lett., 2009, 38, 434-435, 2009.05.
76. M. Hirahara, S. Masaoka and K. Sakai, Bis(2,2'-bipyridine){ethyl4'-[N-(4-carbamoylphenyl)carbamoyl]-2,2'-bipyridine-4-carboxylate}ruthenium(II) bis[hexafluoridophosphate(V)], Acta. Cryst., E65, m228-m229, 2009.02.
77. S. Masaoka and K. Sakai, Clear Evidence Showing the Robustness of a Highly Active Oxygen-Evolving Mononuclear Ruthenium Complex with an Aqua Ligand, Chem. Lett., 38, 182-3, 2009.02.
78. M. Kobayashi, S. Masaoka and K. Sakai, Synthesis, Crystal Structure, Solution and Spectroscopic Properties, and Hydrogen-Evolving Activity of [K(18-Crown-6)][Pt(II)(2-phenylpyridinato)Cl2], Photochem. Photobiol. Sci., 8, 196-203, 2009.01.
79. T. Yamaguchi, S. Masaoka and K. Sakai, Bis(triethylammonium) bis(μ-pyrazine-2,3-dithiolato)bis(pyrazine-2,3-dithiolato)diferrate(III) methanol disolvate, Acta. Cryst., 2009, E65, m77-m78, 2009.01.
80. T. Yamaguchi, S. Masaoka and K. Sakai, Diaqua(1,4,7,10,13-pentaoxacyclopentadecane)iron(II) bis(μ-cis-1,2-dicyano-1,2-ethylenedithiolato)bis[(cis-1,2-dicyano-1,2-ethylenedithiolato)ferrate(III)]1,4,7,10,13-pentaoxacyclopentadecanedisolvate, Acta. Cryst., 2008, E64, m1557, 2008.11.
81. M. Kobayashi, S. Masaoka and K. Sakai, N-(1,10-phenanthrolin-5-yl)-4-(pyridin-2-yl)benzamide monohydrate, Acta. Cryst., 2008, E64, o1979, 2008.09.
82. M. Kobayashi, S. Masaoka and K. Sakai, Chrolo(dimethylsulfoxide)(phenylpyridinato)platinum(II), Acta. Cryst., 2008, E64, m1325, 2008.09.
83. Leoni A. Barrios, Guillem Aromi, Jorge Salinas Uber, Olivier Roubeau, Ken Sakai, Shigeyuki Masaoka, Patrick Gamez and Jan Reedijk, A Mixed-Valence [MnIIMnIIIMnII] Complex of a Linear Phenol-bis-pyrazole Ligand with an S = 3 Spin Ground State, Eur. J. Inorg. Chem., 2008, 24, 3871-3876, 2008.08.
84. H. El-Ghamry, R. Issa, K. El-Baradie, K. Isagai, S. Masaoka and K. Sakai, 4-[(3-Formyl-4-hydroxyphenyl)diazenyl]-N-(pyrimidin-2-yl)benzenesulfonamide, Acta. Cryst., 2008, E64, o1673-o1674, 2008.07.
85. M. J. Katz, K. Sakai and D. B. Leznoff, The use of aurophilic and other metal-metal interactions as crystal engineering design elements to increase structural dimensionality, Chem. Soc. Rev., 2008, 37(9), 1884-95., 2008.07.
86. H. El-Ghamry, R. Issa, K. El-Baradie, K. Isagai, S. Masaoka and K. Sakai, 1-[4-(Diaminomethyleneaminosulfonyl)phenyliminiomethyl]-2-naphtholate N,N-dimethylformamide disolvate, Acta. Cryst., 2008, E64, o1350-o1351, 2008.06.
87. G. Bhargava, A. Anand, M. Mahajan, T. Saito, K. Sakai and C. Medhi, Regio- and π -facial selective Lewis acid interceded Diels-Alder reactions of α -dienyl-β -lactams: an indepth analysis, Tetrahedron, 2008, 64(28), 6801-6808, 2008.04.
88. Ken Sakai and Hironobu Ozawa, Homogeneous catalysis of platinum(II) complexes in photochemical hydrogen production from water, Coordination Chemistry Reviews, 251, 2753-2766, 2007.11.
89. Singo Ogata, Shigeyuki Masaoka, Ken Sakai and Tsuyoshi Satoh, The first example of regiospecific magnesium carbenoid 1,3-CH insertion: its mechanism and stereochemistry, Tetrahedron Letters, 48, 5017-5021, 2007.07.
90. Hironobu Ozawa and Ken Sakai, An Effect of Structural Modification in the Photo-hydrogen-evoluting RuIIPtII Dimers, Chemistry Letters, 36, 920-921, 2007.07.
91. Hironobu Ozawa, Yuki Yokoyama, Masa-aki Haga, and Ken Sakai, Syntheses, Characterization, and Photo-Hydrogen-Evolving Properties of Tris(2,2´-bipyridine)ruthenium(II) Derivatives Tethered to a cis-Pt(II)Cl2 Unit: Insights into the Structure-Activity Relationship, Dalton Trans., 12, 1197-1206, 2007.05.
92. Ken Sakai, Kazuo Yokokawa, and Yoshimi Yokoyama, Pt2II and Pt2III dimers containing a Pt2(2,2\'-bipyridine)2(μ-N,N-dimethylguanidinato)2 unit, Acta Crystallogr., C63, m36-m41, 2007.02.
93. Hiromichi Egami, Ryo Irie, Ken Sakai, and Tsutomu Katsuki, Enantioselective Epoxidation of Conjugated Z-Olefins with Newly Modified Mn(salen) Complex, Chemistry Letters, 36, 46-47, 2007.01.
94. Ken Sakai, Yuki Yokoyama, and Shigeyuki Masaoka, cis-Dichlorobis(4-methylpyridine-κN)platinum(II), Acta Crystallogr., E63, m97-m99, 2007.01.
95. Tsuyoshi Sato, Mariko Miura, Ken Sakai, Yoshimi Yokoyama, Reaction of magnesium cyclopropylidene with N-lithio arylamines: a method for generation of a-amino-substituted cyclopropylmagnesiums and a study for their reactivity with electrophiles, Tetrahedron, 4253-4261, 2006.05.
96. Hironobu Ozawa, Masa-aki Haga, Ken Sakai, A Photo-Hydrogen-Evolving Molecular Device Driving Visible-Light-Induced EDTA-Reduction of Water into Molecular Hydrogen, J.Am.Chem.Soc., 4926-4927, 2006.04.
97. Ken Sakai, Hironobu Ozawa, Hajime Yamada, Taro Tsubomura, Mariko Hara, Akon Higuchi, Masa-aki Haga, A Tris(2,2'-bipyridine)ruthenium(II)Derivative Tetherred to a cis-PtCl2(amine)2moiety:Syntheses, Spectroscopic properties, and Visible-Light-Induced Scission of DNA, Dalton Trans., 3300-3305, 2006.04.
98. Mina Mizota, Yoshimi Yokoyama, and Ken Sakai, Tetrakis(2-thiopydridone)platinum(II) chloride, Acta Crystallogr., E61, m1433-m1435, 2005.01.
99. Hitomi Shiraishi, Reiko Jikido, Kanako Matsufuji, Tatsuaki Nakanishi, Takuya Shiga, Masaaki Ohba, Ken Sakai, Hiroshi Kitagawa, and Hisashi Okawa, Dinuclear Mn(II), Ni(II), and Zn(II) Complexes Bridged by Bis(p-nitrophenyl) Phosphate Ion: Relevance to Bimetallic Phosphodiesterase, Bull. Chem. Soc. Jpn., 10.1246/bcsj.78.1072, 78, 6, 1072-1076, 78, 1072-1076, 2005.01.
100. Construction of Pseudo-Heterochiral and -Homochiral Di-μ-oxotitanium(Schiff base) Dimers and Enantioselective Epoxidation Using Aqueous Hydrogen Peroxide.
101. Tomona Yutaka, Shinya Obara, Masa-aki Haga, Yoshimi Yokoyama, and Ken Sakai, (2,2'-Bipyridine)chloro(4'-tolyl-2,2':6',2''-terpyridine)iridium(III) bis(hexafluorophosphate) acetonitrile disolvate, Acta. Crystallogr., 10.1107/S1600536805018702, 61, M1357-M1359, E61, m1357-m1359, 2005.01.
102. Gaurav Bhargava, Mohinder P. Mahajan, Takao Saito, Takashi Otani, Mai Kurashima, Ken Sakai, Highly Diasteroselective and Remarkably -Facially Selective Lewis Acid-Catalysed Diels-Alder Cycloaddition Reactions: Access to Novel 1,3,4-Trisubstituted 2-Azetidinones, Eur. J. Org. Chem., 2397-2405, 2005.01.
103. Tomona Yutaka, Shinya Obara, Satoshi Ogawa, Koichi Nozaki, Noriaki Ikeda, Takeshi Ohno, Youichi Ishii, Ken Sakai, and Masa-aki Haga, Syntheses and Properties of Emissive Iridium(III) Complexes with Tridentate Benzimidazole Derivatives, Inorg. Chem., 10.1021/ic048622z, 44, 13, 4737-4746, 44, 4737-4746, 2005.01.
104. Mitsuru Shoji, Hiroki Imai, Makoto Mukaida, Ken Sakai, Hideaki Kakeya, Hiroyuki Osada, and Yujiro Hayashi, Total Synthesis of Epoxyquinols A, B, and C and Epoxytwinol A and the Reactivity of a 2H-Pyran Derivative as the Diene Component in the Diels-Alder Reaction, J. Org. Chem., 70, 79-91, 2005.01.
105. Tomoaki Tanase, Eri Goto, Rowshan A. Begum, Makiko Hamaguchi, Shuzhong Zhan, Masayasu Iida, and Ken Sakai, Reactive Rigid-Rod Organometallic Polymers Involving Linear Triplatinum Units Connected by p-Conjugated Bisisocyanides, Organometallics, 23, 5975-5988., 2004.01.
106. Eri Goto, Miho Usuki, Hiroe Takenaka, Ken Sakai, and Tomoaki Tanase, Electron-Rich Diplatinum(0) Metallocryptate Promoting Novel Successive Encapsulation of Acidic Hydrides, Organometallics, 23, 6042-6051, 2004.01.
107. Eri Goto, Rowshan A. Begum, Shuzhong Zhan, Tomoaki Tanase, Katsumi Tanigaki, and Ken Sakai, Linear, Redox-Active Pt6 and Pt2Pd2Pt2 Clusters, Angew. Chem. Int. Ed., 43, 5029-5032., 2004.01.
108. Ken Sakai, Yoshimi Yokoyama, Hideki Hama, Kaoru Kato, Yoshie Ikuta, Taro Tsubomura, and Tomoaki Tanase, Bis[μ-3-(N'-methyl-4,4'-bipyridinium-1-yl)propionamidato] bis[cis-diammineplatinum(II)] hexaperchlorate dihydrate in a head-to-tail isomerism, Acta Crystallogr., E60, m664-m667, 2004.01.
109. Kazuo Yokokawa and Ken Sakai, Di-μ-pivalamidato-κ4N,O-bis[(sulfato)(2,2'-bipyridine-κ2N,N')platinum(III)] tetrahydrate in a head-to-tail isomerism, Acta Crystallogr., C60, m244-m247, 2004.01.
110. Mina Mizota and Ken Sakai, Di-μ-aminopyridinato-bis[(2,2'-bipyridine)platinum(II)] dinitrate tetrahydrate in a head-to-tail isomerism, Acta Crystallogr., E60, m473-m476, 2004.01.
111. Ken Sakai, Yosuke Konno, Noboru Takayama, and Satoru Takahashi, The First Bent Form for the Hydroxo-Bridged cis-Diammineplatinum(II) Dimer: [Pt2(NH3)4(m-OH)2](ClO4)2, Acta Crystallogr., B60, 255-262, 2004.01.
112. Ken Sakai, Itsuki Sakai, Neil D. Draper, Daniel B. Leznoff, Di-μ-α-pyrrolidinonatobis[cis-diammineplatinum(II)] sulfate hydrate in a Head-to-Head isomerism, Acta Crystallogr., E60, m273-m276, 2004.01.
113. Ken Sakai, Itsuki Sakai, Takashi Kajiwara, and Tasuku Ito, Di-μ-α-pyrrolidinonatobis[cis-diamminechloroplatinum(III)] sulfate dihydrate: a head-to-head isomer, Acta Crystallogr., E60, m255-m258., 2004.01.
114. Ken Sakai and Yoshinobu Miyabe, (1,10-Phenanthroline)bis(2,2'-bipyridine)ruthenium(II) tetracyanoplatinate(II), Acta Crystallogr., C60, m69-m72, 2004.01.
115. Ken Sakai, Yuichi Uchida, Takashi Kajiwara, and Tasuku Ito, Bis[tris(2,2'-bipyridine)ruthenium(II)] hexacyanoferrate(III) chloride octahydrate, Acta Crystallogr., C60, m65-m68, 2004.01.
116. Ken Sakai, Mina Mizota, and Norinobu Akiyama, Bis(2-aminopyridine)(2,2'-bipyridine)platinum(II) tetracyanoplatinate(II) dihydrate, Acta Crystallogr., E60, m88-m90, 2004.01.
117. Ken Sakai and Eri Ishigami, Bis[di-μ-isobutyratobis[cis-diammineplatinum(II)]] tetrakis(perchlorate), Acta Crystallogr., E60, m65-m68, 2004.01.
118. Ken Sakai, Eri Ishigami, Kazuo Yokokawa, Takashi Kajiwara and Tasuku Ito, Di-μ-pivalato-bis[cis-diammineplatinum(II)] bis(perchlorate) pivalic acid solvate, Acta Crystallogr., E59, m1178-m1180, 2003.01.
119. Tsuyoshi Satoh, Tadashi Kawashima, Satoru Takahashi, and Ken Sakai, A new synthesis, including asymmetric synthesis, of spiro[4.n]alkenones from three components: cyclic ketones, chloromethyl p-tolyl sulfoxide, and acetonitrile; and a formal total synthesis of racemic acorone, Tetrahedron, 59, 9599-9607, 2003.01.
120. Tsuyoshi Satoh, Takayuki Shimura, and Ken Sakai, The first examples of an amide-carbonyl stabilized oxiranyl anion: generation from epoxysilane, its properties, and trapping with electrophiles, Heterocycles, 59, 137-147, 2003.01.
121. Ken Sakai, Yoshie Ikuta, Taro Tsubomura, Kaoru Kato, Yoshimi Yokoyama, Takashi Kajiwara and Tasuku Ito, A head-to-tail isomer of bis[μ-2-(N'-methyl-4,4'-bipyridinium-1-yl)-acetamidato]bis[cis- diammineplatinum(II)] hexaperchlorate dihydrate, Acta Crystallogr., E59, m780-m783, 2003.01.
122. Ken Sakai, Norinobu Akiyama, and Mina Mizota, Bis(2-aminopyridine)(2,2'-bipyridine)platinum(II) bis(oxalato)platinate(II) dihydrate, Acta Crystallogr., E59, m636-m638, 2003.01.
123. Ken Sakai, Mai Kurashima, Norinobu Akiyama, Naoki Satoh, Takashi Kajiwara and Tasuku Ito, A head-to-head isomer of di-μ-pivalamidatobis[(1,10-phenanthroline)platinum(II)] dinitrate dihydrate, Acta Crystallogr., C59,m345-m349, 2003.01.
124. Ken Sakai, Meiko Shiomi, Taro Tsubomura, Kaoru Kato, Yoshimi Yokoyama, Takashi Kajiwara, and Tasuku Ito, A head-to-head isomer of di-μ-bis(N-methylisonicotinamidato)bis[cis-diammineplatinum(II)] tetraperchlorate, Acta Crystallogr., E59, m559-m561, 2003.01.
125. Ken Sakai, Tomohiko Sakamoto, Takashi Kajiwara, and Tasuku Ito, A head-to-head isomer of di-μ-α-pyrrolidinonatobis[cis-bromodiammineplatinum(III)] dinitrate, Acta Crystallogr., E59, m553-m555, 2003.01.
126. Ken Sakai and Satoru Takahashi, A head-to-head isomer of Bis{di-μ-(5-carboxy-a-pyridonato)bis[cis-diammineplatinum(II)]} tetranitrate dihydrate, Acta Crystallogr., E59, m532-m535, 2003.01.
127. Ken Sakai, Yoshimi Yokoyama, Ken Okamoto, and Satoru Takahashi, Dichloro(4-amino-2,2'-bipyridine)platinum(II) dihydrate, Acta Crystallogr., E59, m518-m520, 2003.01.
128. Ken Sakai, Mai Kurashima, Manabu Osada, and Satoru Takahashi, (N-methyl-4,4'-bipyridinium)(2,2':6',2"-terpyridine)platinum(II) triperchlorate hydrate, Acta Crystallogr., E59, m515-m517, 2003.01.
129. Ken Sakai, Manabu Osada, Yoshimi Yokoyama, Yasushi Tomita, and Taro Tsubomura, (2,2'-Bipyridine)bis(N-methyl-4,4'-bipyridinium)platinum(II) tetraperchlorate, Acta Crystallogr., E59, m512-m514, 2003.01.
130. Ken Sakai, Norinobu Akiyama, and Mina Mizota, Bis(2-aminopyridine)(2,2'-bipyridine)platinum(II) dinitrate dihydrate, Acta Crystallogr., E59, m459-m461, 2003.01.
131. Yujiro Hayashi, Tsuboi, Wataru Tsuboi, Ashimine, Itaru Ashimine, Tatsuya Urushima, Mitsuru, Shoji, and Ken Sakai, The Direct and Enantioselective, One-pot, Three-component, Cross-Mannich Reaction of Aldehydes, Angew. Chem. Int. Ed., 42, 3677-3680, 2003.01.
132. Ken Sakai, Ken Okamoto, Satoru Takahashi, and Kazuo Yokokawa, N-Methyl-N'-(3-phthalimidopropyl)-4,4'-bipyridinium diiodide, Acta Crystallogr., E59, o917-o918, 2003.01.
133. Ken Sakai, Eri Ishigami, Kazuo Yokokawa, Takashi Kajiwara, and Tasuku Ito, Di-μ-pivalatobis[cis-diammineplatinum(II)] sulfate hydrate, Acta Crystallogr., E59, m443-m445, 2003.01.
134. Ken Sakai, Mai Kurashima, [μ-2,3,5,6-Tetrakis(2-pyridyl)pyrazine]bis[chloroplatinum(II)] Bis[trichloro(dimethylsulfoxide-S)platinate(II)], Acta Crystallogr., E59, m411-m413, 2003.01.
135. Ken Sakai, Norinobu Akiyama, Mina Mizota, Kazuo Yokokawa, and Yoshimi Yokoyama, Bis(guanidinium) bis(oxalato)platinate(II), Acta Crystallogr., E59, m408-m410, 2003.01.
136. Ken Sakai, Eri Ishigami, Yosuke Konno, Takashi Kajiwara, and Tasuku Ito, New Partially-Oxideized 1-D Platinum Chain Complexes Consisting of Carboxylate-Bridged cis-Diammineplatinum Dimer Cations, J. Am. Chem. Soc., 58, 9213-9222, 2002.09.
137. Tadahiro Kato, Masahiro Hoshikawa, Yoshihiro Yaguchi, Kiyokazu Izumi ,Yukio Uotsu and Ken Sakai, Synthesis of dl-12-Epiverticillol, Tetrahedron, 58, 9213-9222, 2002.01.
138. Yujiro Hayashi, Mitsuru Shoji, Junichiro Yamaguchi, Kenji Sato, Shinpei Yamaguchi, Takasuke Mukaiyama, Ken Sakai, Yukihiro Asami, Hideaki Kakeya, Hiroyuki Osada, Asymmetric Total Synthesis of (-)-Azaspirene, a Novel Angiogenesis Inhibitor, J. Am. Chem. Soc., 124, 12078-12079, 2002.01.
139. Tsuyoshi Satoh, Noriko Hanaki, Yuko Kuramochi, Yujiro Inoue, Kayo Hosoya, and Ken Sakai, A new method for synthesis of allenes, including an optically active form, from aldehydes and alkenyl aryl sulfoxides by sulfoxide-metal exchange as the key reaction and an application to a total synthesis of male bean weevil sex attractant, Tetrahedron, 58, 2533-2549, 2002.01.
140. T. Tsubomura, Takayuki Tanihata, Tetsuya Yamakawa, Rakuko Ohmi, Tsuyoshi Tamane, Akon Higuchi, Akira Katoh, and K. Sakai, Synthesis and Structure of New Binuclear Organopalladium Macrocyclic Complexes, Organometallics, 20,3833-3835, 2001.01.
141. T. Tsubomura, M. Ezawa, T. Sato and K. Sakai, A Hexaimino Cryptand containing Naphthyl Groups ; Structural Characterization of Mononuclear Complexes and Catalysis in Hydrolysis of p-Nitro Phosphate, Inorg. Chim. Acta, 310,265-267, 2000.01.
142. Akon Higuchi, Shinya Adachi, Takeshi Imizu, Yoon Boo Ok, Taro Tsubomura, Mariko Hara, and Ken Sakai, Ocillation of Membrane Potential in Immobilized DNA Membranes, J. Phys. Chem. B, 104, 9864-9872, 2000.01.
143. Ken Sakai, Yasushi Tomita, Takuma Ue, Koji Goshima, Masakatsu Ohminato, Taro Tsubomura, Kazuko Matsumoto, Kenji Ohmura, and Kazuyuki Kawakami, Syntheses, Crystal Structures, and Molecular Mechanics Studies of a New Antitumor-Active cis-PtCl2(pzH)2 (pzH=Pyrazole) and the Related Complexes. A Novel Magnus-Type Double-Salt [Pt(pzH)4][PtCl4][cis-PtCl2(pzH)2]2 Involving Two Perpendicularly Aligned 1D Chains, Inorg. Chim. Acta, 297/1-2, 64-71, 2000.01.
144. Kazuko Matsumoto and Ken Sakai, Structures and Reactivities of Platinum-Blues and the Related Amidate-Bridged PlatinumIII Compounds, Adv. Inorg. Chem., 49, 375-427, 1999.01.
145. Ken Sakai, and Taro Tsubomura, Recent Development in the Platinum-Blue Chemistry, 4, 295-300, 1999.01.
146. Masami Ito, Ken Sakai, Taro Tsubomura, and Yu-saku Takita, Transesterification by (Hydroxo)nickel(II) Complex in the Presence of External Alcohol, Bull. Chem. Soc. Jpn., 72, 239-247, 1999.01.
147. Taro Tsubomura, Mitsuru Ito, and Ken Sakai, 18-Membered Tetraimino Macrocyclic Complexes Containing Furan Groups; Stacking of Two Macrocycles and Characterization of Organic Derivatives, Inorg. Chim. Acta, 284, 149, 1999.01.
148. Masami Ito, Yu-saku Takita, Ken Sakai,and , Taro Tsubomura, The Syntheses of (Chloro) Iron(II) Complexes by Using Tridentate Polypyridine Ligands, Chem. Lett., 1185, 1998.01.
149. Ken Sakai, Masao Takeshita, Yuko Tanaka, Takuma Ue, Masayuki Yanagisawa, Masaya Kosaka, Taro Tsubomura, and Masamichi Ato, A New One-Dimensional Platium System Consisting of Carboxylate-Bridged cis-Diammineplatinum Dimers, J. Am. Chem. Soc., 120, 11353-11363, 1998.01.
150. Ken Sakai, Yuko Tanaka, Yuriko Tsuchiya, Kentaro Hirata, Taro Tsubomura, Seiichiro Iijima, and Ashis Bhattacharjee, New Structural Aspects of a-Pyrrolidinonate-Bridged and a-Pyridonate-Bridged, Homo- and Mixed-Valence, Di- and Tetranuclear cis-Diammineplatinum Complexes: Eight New Crystal Structures, Stoichiometric 1:1 Mixture of Pt(2.25+)4 and Pt(2.5+)4, New Quasi-One-Dimensional Halide-Bridged [Pt(2.5+)4-Cl・・・]\ System, and Consideration for Solution Propertie, J. Am. Chem. Soc., 120, 8366-8379, 1998.01.
151. Taro Tsubomura, and Ken Sakai, Photochemical Reactions of Palladium(0) and Platinum(0) Phosphine Complexes, Coord. Chem. Rev., 171, 107-113, 1998.01.
152. Miho Hashioka, Ken Sakai, and Taro Tsubomura, Bis[m-methylenebis(dicyclohexylphosphine)-P:P']bis[chloropalladium(I)](Pd-Pd) Diacetonitrile Solvate, Acta Crystallogr., C54, 1244-1247, 1998.01.
153. Taro Tsubomura, Akira Ishikura, Kenta Hoshino, Hiroki Narita, and Ken Sakai, Photochemical C-C Bond Formation from Chlorobenzene Mediated by [Pd(PPh3)4], Chem. Lett., 1171-1172, 1997.01.
154. Synthesis, Characterization, and Interaction with DNA of A New Cis-Diamminedichloroplatinum(II)-Derivative Having a Polypyridyl Ruthenium(II) Emitter.
155. Ken Sakai,Yoshie Ikuta, Meiko Shiomi, Tsuyoshi Tamane, Yasushi Tomita, Taro Tsubomura, and Nobukatsu Nemoto, Syntheses, Structures, and Conformational Studies of N-Carbamoylmethylpyridinium Perchlorate and N-Carbamoylmethyl-N'-methyl-4,4'-bipyridinium Bis(perchlorate) Hydrate, Acta Crystallogr.,, C53, 331-334, 1997.01.
156. Shigenobu Yano, Tomoko Inagaki, Yasuko Yamada, Masako Kato, Mikio Yamasaki, Ken Sakai, Taro Tsubomura, Mitsunobu Sato, Wasuke Mori, Kazuya Yamaguchi, and Isamu Kinoshita, A Novel Tetranuclear Iron(III) Complex having L-Alanine Bridges and an Unprecedented (Fe4(OH2)) Core, Chem. Lett., 61, 1996.01.
157. Motowo Yamaguchi, Masayuki Yabuki, Takamichi Yamagishi, Ken Sakai, and Taro Tsubomura, Molecular Structure of 1,3-Disubstituted p-Allyl Palladium(II) Complexes with a Chiral Diphosphine: The Intermediate of Palladium-catalyzed Asymmetric Allylic Alkylation, Chem. Lett., 241-242, 1996.01.
158. Mitsuru Ito, Tadanobu Sato, Ken Sakai, and Taro Tsubomura, Triple-Decker Sandwich Structure of a New Rubidium(I) Tetraimino Macrocyclic Complex, Chem. Lett., 1996, 619-620, 1996.01.
159. Ken Sakai, Yasutaka Yamada, and Taro Tsubomura, Syntheses and Crystal Structures of Ruthenium Complexes of 1,4,8,11-Tetraazacyclotetradecane, Tris(2-aminoethyl)amine (tren) and Bis(2-aminoethyl)(iminomethyl)amine. A Microporous Layered Structure Consisting of {[K(tren)]2[RuCl6]}nn- and {(H5O2)4[RuCl6]}nn+, Inorg. Chem., 35, 3163-3172, 1996.01.
160. Tadanobu Sato, Harumi Takeda, Ken Sakai, and Taro Tsubomura, Novel Two Types of Metal Complexes Derived from Tripod Amines and Acetylacetone, Inorg. Chim. Acta, 246, 413-421, 1996.01.
161. Tadanobu Sato, Ken Sakai, and Taro Tsubomura, A Cryptand Containing Three Diiminopyridyl Units; Aromatic-Aromatic Interaction and the Stability of the Complexes, Supramol. Chem., 7, 157-165, 1996.01.
162. Ken Sakai, Yasutaka Yamada, Taro Tsubomura, Masayuki Yabuki, and Motowo Yamaguchi, Synthesis, Crystal Structure, and Solution Properties of a Hexacopper(II) Complex with Bridging Hydroxides, Pyrazolates and Nitrates, Inorg. Chem., 35, 542-544, 1996.01.
163. Ken Sakai, Tadanobu Sato, Taro Tsubomura, and Kazuko Matsumoto, Di-m-pyrazolato-N:N'-bis[(2,2'-bipyridine-N:N')platinum(II)] Bis(tetrafluoroborate) Monohydrate, Acta Crystallogr., C52, 783-786, 1996.01.
164. Ken Sakai, Akira Ishikura, Taro Tsubomura, and Kazuko Matsumoto, Two Different Crystal Forms of cis-Diamminebis(pyrazole)platinum(II) Dinitrate, Acta Crystallogr., C52, 779-783, 1996.01.
165. [MnIII4(m3-O)2(m-O2CMe)7(2,2'-bipyridine)2](ClO4).
166. Tadanobu Sato, Atsushi Suzuki, Ken Sakai, and Taro Tsubomura, Syntheses and Structures of a Novel Trinaphthylene Hexaimino Cryptand: Three Different Conformations of a Macrobicyclic Ligand, Bull. Chem. Soc. Jpn., 69, 379-388, 1996.01.
167. Ken Sakai, Yuko Tanaka, and Taro Tsubomura, [N,N'-Bis(2-aminoethyl-N)-N,N'-bis(2-ammonioethyl)ethylenediamine-N,N']platinum(II) Bis(tetrachloroplatinate) Trihydrate, Acta Crystallogr., C52, 541-543, 1996.01.
168. Hiroshi Tominaga, Ken Sakai, and Taro Tsubomura, Structure and Photophysical Properties of [Pt0(BINAP)2] (BINAP = 2,2'- bis(diphenylphosphino)-1,1'-binaphthyl), J. Chem. Soc., Chem. Commun., 2273-2274, 1995.01.
169. Masako Kato, Yasuko Yamada, Tomoko Inagaki, Wasuke Mori, Ken Sakai, Taro Tsubomura, Mitsunobu Sato, and Shigenobu Yano, Structures and Magnetic Properties of Iron(III) Dinuclear Complexes with Alkoxo and Carboxylato Bridges, Inorg. Chem., 34, 2645-2651, 1995.01.
170. Jiro Abe, Yasuo Shirai, Ken Sakai, and Taro Tsubomura, Ab Initio MO and X-ray Studies of Excited States in Molecular Crystals of 4-(b,b-Dicyanovinyl)-3-methyl-N-methyl-N-benzylaniline, J. Phys. Chem., 99, 8108-8120, 1995.01.
171. Ken Sakai, Taro Tsubomura, and Kazuko Matsumoto, Reactions of an a-Pyrrolidonate-Bridged cis-Diammineplatinum(II) Dimer with Molecular Oxygen and Its Application to the Catalytic O2 Oxidation of Hydroquinone, Inorg. Chim. Acta, 234, 157-161, 1995.01.
172. Taro Tsubomura, Atsushi Itsuki, Masahiko Homma, and Ken Sakai, Photoreaction of Palladium Phosphine Complex with Chloroalkane. Production of Ethylene with 1,2-Dichloroethane and Novel Photochromic Behavior, Chem. Lett., 661-664, 1994.01.
173. Tadanobu Sato, Ken Sakai, and Taro Tsubomura, Conformational Change of a Macrobicyclic Complex. Structure of Free Ligand and Interactions with DMSO, Chem. Lett., 859-862, 1993.01.
174. Ken Sakai, Taro Tsubomura, and Kazuko Matsumoto, Redox Disproportionation Cleavage of an a-Pyrrolidonate-Bridged Mixed-Valent Tetranuclear Platinum Complex, Inorg. Chim. Acta, 213, 11-16, 1993.01.
175. Ken Sakai, Yukio Kizaki, Taro Tsubomura, and Kazuko Matumoto, Homogeneous Catalysis of Mixed-Valent Octanuclear Platinum Complexes in Photochemical Hydrogen Production from Water, J. Mol. Catal., 79, 141-152, 1993.01.
176. Ken Sakai, Yuriko Tsuchiya, and Taro Tsubomura, Axial Ligand Substitution Equilibria with Chloride Anion on a-Pyrrolidonate-Bridged cis-Diammineplatinum(III) Dimer, Technol. Rep. Seikei Univ., 54, 77-78, 1992.01.
177. Taro Tsubomura, Tadanobu Sato, Kouichi Yasaku, Ken Sakai, Kimiko Kobayashi, and Makoto Morita, Synthesis and Characterization of Barium(II) Macrobicyclic Complexes and Related Compounds, Chem. Lett., 731-734, 1992.01.
178. Kazuko Matsumoto, Ken Sakai, Kyosuke Nishio, Yasuhiro Tokisue, Reikichi Ito, Toshikazu Nishide, and Yushi Shichi, Syntheses, Crystal Structures, and Electronic, ESR and X-Ray Photoelectron Spectra of Acetamidate- and 2-Fluoroacetamidate-Bridged Mixed-Valent Octanuclear Platinum Blues, J. Am. Chem. Soc., 114, 8110-8118, 1992.01.
179. Masaki Kawano, Chikara Hoshino, Ken Sakai, and Kazuko Matsumoto, Crystal Structure of cis-Bis(acetonitrile)tetrakis(trimethylphosphite)iron(II) Tetrachlorotetrakis(m3-sulfido)tetraferrate(2II,2III), Anal. Sci., 7, 829-830, 1991.01.
180. Ken Sakai, Kazuko Matsumoto, and Kyosuke Nishio, Crystal Structure of 2-Fluoroacetamidate-Bridged Mixed-Valent Octanuclear Platinum Blue with Average Platinum Oxidation State of 2.08, [Pt8(NH3)16(CH2FCONH)8](NO3)8.66・4H2O, Chem. Lett., 1081-1084, 1991.01.
181. Ken Sakai, and Kazuko Matsumoto, Oxidation of Benzene to Phenol with Hydrogen Peroxide Catalyzed by a-Pyrrolidonate-Bridged Mixed-Valent Tetranuclear Platinum Complexes, J. Mol. Catal., 67, 7-18, 1991.01.
182. Ken Sakai, and Kazuko Matsumoto, Homogeneous Catalysis of Platinum Blue Related Complexes in Photoreduction of Water into Hydrogen, J. Mol. Catal., 62, 1-14, 1990.01.
183. Ken Sakai, and Kazuko Matumoto, Photochemical Reduction of Water to Hydrogen Catalyzed by Mixed-Valent Tetranuclear Platinum Complex, J. Coord. Chem., 18, 169-172, 1988.01.
184. Ken Sakai, and Kazuko Matsumoto, Mixed-Valent Octanuclear Platinum Acetamide Complex, [Pt8(NH3)16(C2H4NO)8]10+, J. Am. Chem. Soc., 111, 3074-3075, 1989.01.