KINDAI UNIVERSITY


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OKUBO Takashi

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FacultyDepartment of Science / Graduate School of Science and Engineering Research / Research Institute for Science and Technology
PositionProfessor
Degree
Commentator Guidehttps://www.kindai.ac.jp/meikan/345-ookubo-takashi.html
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Last Updated :2020/07/11

Education and Career

Education

  •   1990 04  - 1994 03 , Tokyo Metropolitan University, Graduate School of Science
  •   1994 04  - 1996 03 , Tokyo Metropolitan University, Graduate School of Science
  •   1996 04  - 1999 03 , Tokyo Metropolitan University, Graduate School of Science

Academic & Professional Experience

  •   2018 04 ,  - 現在, Professor, Faculty of Science and Engineering, Kindai University
  •   2011 04 ,  - 2018 03 , Associate Professor, Faculty of Science and Engineering, Kindai University
  •   2016 04 ,  - 2017 03 , Visiting Researcher, University of California, Santa Barbara
  •   2012 10 ,  - 2016 03 , PRESTO, JST
  •   2007 10 ,  - 2011 03 , PRESTO, JST
  •   2007 04 ,  - 2011 03 , Assistant Professor, Faculty of Science and Engineering, Kindai University
  •   2000 03 ,  - 2007 03 , Research Associate at Japan Advanced Institute of Science & Technology, JAIST
  •   2004 04 ,  - 2006 03 , Postdoctoral Fellowships for Research Abroad of Japan Society for the Promotion of Science, Northwestern University, JSPS
  •   1999 04 ,  - 2000 02 , Special Research Associate at the Institute of Physical and Chemical Research, RIKEN
  •   1996 04 ,  - 1999 03 , Research Fellow of the Japan Society for the Promotion of Science, JSPS

Research Activities

Research Areas

  • Nanotechnology/Materials, Inorganic and coordination chemistry
  • Nanotechnology/Materials, Functional solid-state chemistry

Research Interests

  • Alq_3

Published Papers

  • Spectroscopic characterization of valence tautomeric behavior in a cobalt- dioxolene complex using an ancillary ligand containing quinoline groups, Takuto Mibu, Yusaku Suenaga, Takashi Okubo, Masahiko Maekawa, Takayoshi Kuroda-Sowa, Inorganic Chemistry Communications, Inorganic Chemistry Communications, 114, Feb. 2020 , Refereed
  • Self-assembly of Cu(I) metallomacrocycle and coordination polymers with 2, 2′:5′,4″-terpyridine directed by anions and solvents, Masahiko Maekawa, Terumasa Hayashi, Kunihisa Sugimoto, Takashi Okubo, Takayoshi Kuroda-Sowa, Inorganica Chimica Acta, Inorganica Chimica Acta, 497, Aug. 2019 , Refereed
  • Crystal structure of a dinuclear Co complex with doubly bridged fluorides: di-μ-fluoride-bis{(2-pyridylmethyl)bis(2-quinolylmethyl)}amine dicobalt(II) bis (tetrafluoroborate), [Co2(μ-F)2(pbqa)2](BF4)2, Y. Suenaga, T. Mibu, T. Okubo, M. Maekawa, T. Kuroda-Sowa, X-ray Struct. Anal. Online, X-ray Struct. Anal. Online, 35(10), 61 - 62, 2019 , Refereed
  • Syntheses, structure and properties of di-nuclear Co complexes with bis(catecholate) ligands-effect of a quinoline ring in the terminal group, Y. Suenaga, T. Mibu, T. Okubo, M. Maekawa, T. Kuroda-Sowa, Polyhedron, Polyhedron, 171, 480 - 485, 2019 , Refereed
  • Measuring the competition between bimolecular charge recombination and charge transport in organic solar cells under operating conditions, Michael C. Heiber, Takashi Okubo, Seo-Jin Ko, Benjamin R. Luginbuhl, Niva A. Ran, Ming Wang, Hengbin Wang, Mohammad, Afsar Uddin, Han Young Woo, Guillermo C. Bazan, Thuc-Quyen Nguyen, Energy & Environmental Science, Energy & Environmental Science, 11, 3019 - 3032, Jul. 2018 , Refereed
  • Crystal Structure and Band-Gap Engineering of a Semiconducting Coordination Polymer Consisting of Copper(I) Bromide and a Bridging Acceptor Ligand., Okubo T, Himoto K, Tanishima K, Fukuda S, Noda Y, Nakayama M, Sugimoto K, Maekawa M, Kuroda-Sowa T, Inorganic chemistry, Inorganic chemistry, 57(5), 2373 - 2376, Mar. 05 2018 , Refereed
  • A new semiconducting coordination polymer consisting of copper(I)-iodide and 3-pyridinecarboxaldehyde, Himoto Kento, Horii Toshiya, Syoji Takumi, Okubo Takashi, Maekawa Masahiko, Kuroda-Sowa Takayoshi, INORGANIC CHEMISTRY COMMUNICATIONS, INORGANIC CHEMISTRY COMMUNICATIONS, 88, 34 - 37, Feb. 2018 , Refereed
  • Crystal structure of a new mixed-metal coordin-ation polymer consisting of NiII piperidine-di-thio-carbamate and penta-nuclear CuI-I cluster units., Himoto K, Horii T, Oda S, Suzuki S, Sugimoto K, Okubo T, Maekawa M, Kuroda-Sowa T, Acta crystallographica. Section E, Crystallographic communications, Acta crystallographica. Section E, Crystallographic communications, 74(Pt 2), 233 - 236, Feb. 2018 , Refereed
  • A new semiconducting 1D Cu(I)–Cu(II) mixedvalence coordination polymer with Cu(II) dimethylpiperidine–dithiocarbamate and a tetranuclear Cu(I)–Br cluster unit, K. Himoto, S. Suzuki, T. Okubo, M. Maekawa, T. Kuroda-Sowa, New J. Chem., 2018, 42, 3995, New J. Chem., 2018, 42, 3995, (42), 3995 - 3998, Feb. 2018 , Refereed
  • Crystal structure of a dinuclear Co complex with doubly bridged fluoride and peroxo ligands: μ-fluoro μ-peroxo bis{tris(2-pyridylmethyl)amine}dicobalt(III) tris(tetrafluoroborate), [Co2(μ-F)(μ-O2)(tpa)2](BF4)3, Y. Suenaga, M. Inomata, K. Uwai, K. Okuda, T. Okubo, M. Maekawa, T. Kuroda-Sowa, X-ray Struct. Anal. Online, X-ray Struct. Anal. Online, 30, 57 - 58, 2014 , Refereed
  • Blue electroluminescent aluminum(III) tris[2-(2-hydroxyphenyl)-5-phenyl-1,3-oxazole], T. –S. Kim, H. Murata, T. Okubo, T. Mitani, Science and Technology of Advanced Materials, Science and Technology of Advanced Materials, 5, 325 - 329, 2014 , Refereed
  • Halido-Bridged 1D Mixed-Valence CuI-CuII Coordination Polymers Bearing a Piperidine-1-carbodithioato Ligand: Crystal Structure, Magnetic and Conductive Properties, and Application in Dye-Sensitized Solar Cells, Tanaka Naoya, Okubo Takashi, Anma Haruho, Kim Kyung Ho, Inuzuka Yoshie, Maekawa Masahiko, Kuroda-Sowa Takayoshi, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, (19), 3384 - 3391, Jul. 2013 , Refereed
  • Tris-(μ4-azepane-1-carbodi-thio-ato)bis-(μ3-azepane-1-carbodi-thio-ato)-μ9-bromido-tetra-μ2-bromido-octa-copper(I)-copper(II)., Okubo T, Anma H, Maekawa M, Kuroda-Sowa T, Acta crystallographica. Section E, Structure reports online, Acta crystallographica. Section E, Structure reports online, 69(Pt 5), m275 - 6, May 2013 , Refereed
  • Abrupt Spin Transitions and LIESST Effects Observed in Fe-II Spin-crossover Complexes with Extended pi-Conjugated Schiff-base Ligands Having N4O2 Donor Sets, Takayoshi Kuroda-Sowa, Zhong Yu, Yuka Senzaki, Kunihisa Sugimoto, Masahiko Maekawa, Megumu Munakata, Shinya Hayami, Yonezo Maeda, CHEMISTRY LETTERS, CHEMISTRY LETTERS, 37(12), 1216 - 1217, Dec. 2008
    Summary:Novel Fe-II complexes with N4O2 donor sets having, extended pi-conjugated aromatic rings, [Fe(qnal)(2)]center dot CH2Cl2 and [Fe(qnal)21, show abrupt spin transitions at 220 and 265 K, respectively. Both complexes show LIESST effects below 80 K.
  • Cobalt(II) and cobalt(III) complexes with 4'-(4-cyanophenyl)-2,2':6',2''-terpyridine., Yu Z, Nabei A, Izumi T, Okubo T, Kuroda-Sowa T, Acta crystallographica. Section C, Crystal structure communications, Acta crystallographica. Section C, Crystal structure communications, 64(Pt 5), m209 - 12, May 2008 , Refereed
  • Blue electroluminescent aluminum (III) tris[2-(2-hydroxyphenyl)-5-phenyl-1, 3-oxazole], T. S. Kim, H. Murata, T. Okubo, T. Mitani, Science and Technology of Advanced Materials, Science and Technology of Advanced Materials, 5, 325 - 329, May 2004 , Refereed
    Summary:Aluminum (III) tris[2-(2-hydroxyphenyl)-5-phenyl-1,3-oxazole] (Alppo 3), has been synthesized as a new efficient blue electroluminescent (EL) material. Alppo3 provided good color purity, high luminance, and high efficiency of blue light-emission in an organic light-emitting device. The EL maximum wavelength is 420 nm and Commission Internationale de l'Eclairage coordinates are x=0.16, y=0.15 of blue color chromaticity. The luminance efficiency and the maximum luminance of Alppo3 device were 3lm/W at 6.05 mA/cm2 (345cd/m2) and 13,900cd/m2, respectively. © 2004 Published by Elsevier Ltd.
  • hird-ordere nonlinear optical properties of a copper(I) trinuclear complex with D3h symmetrical radical ligand, T. Okubo, S. Kitagawa, S. Masaoka, S. Furukawa, M. Kondo, Nonlinear Optics, Nonlinear Optics, 24((num)), 129 - 132, Dec. 2000 , Refereed
  • Synthesis, structure, and reactivities of the Ru-Co heterobimetallic complex. Molecular structures of Cp*Ru(CO)(2)(mu(2)-CO)Co(CO)(3), Cp*Ru(mu(2)-CO)(2)(mu(2)-dppm)Co(CO)(2), Cp*Ru(CNBut)(CO)(mu(2)-CO)Co(CO)(3), and Cp*(CO)Ru{eta(2):eta(4)-mu(2)-C(Tol)CHC(Tol)CH}Co(CO)(2) (Cp* = eta(5)-C5Me5, dppm = Ph2PCH2PPh2, Tol = C6H4Me-4), H Matsuzaka, K Ichikawa, T Ishioka, H Sato, T Okubo, T Ishii, M Yamashita, M Kondo, S Kitagawa, JOURNAL OF ORGANOMETALLIC CHEMISTRY, JOURNAL OF ORGANOMETALLIC CHEMISTRY, 596(1-2), 121 - 129, Feb. 2000 , Refereed
    Summary:Treatment of Cp*Ru(CO)(2)Cl (Cp* = eta(5)-C5Me5) with NaCo(CO)(4) produces the metal-metal bonded heterobimetallic complex Cp*Ru(CO)(2)(mu(2)-CO)Co(CO)(3) (2b). Substitution of the CO ligands by the Ph2PCH2PPh2 (dppm) leads to the isolation of Cp*Ru(mu(2)-CO)(2)(mu(2)-dppm)Co(CO)(2) (3) whereas that by (BuNC)-N-t gives Cp*Ru(CO)(CNBut)(mu(2)-CO)Co(CO)(3) (4). Stoichiometric head-to-tail dimerization of p-tolylacetylene at the bimetallic site of 2b proceeds to form the dinuclear metallacyclopentadiene complex Cp*(CO)Ru{eta(2):eta(4)-mu(2)-C(Tol)CHC(Tol)CH}Co(CO)(2) (5) in which two alkyne molecules are coupled to form a ruthenacyclopentadiene core which coordinates to the Co(CO), fragment. On the other hand, catalytic head-to-head coupling of methyl propiolate in the presence of 2b yields (E)-(MeO2C)CH=CH(C=CCO2Me) (6). The molecular structures of 2b, 3, 4, and 5 have been determined by X-ray crystallography. (C) 2000 Elsevier Science S.A. All rights reserved.
  • Synthesis and molecular structure of the amido-bridged dinuclear rhodium complex [Cp*Rh{μ2-(NH)2C10H6-2,3}(μ2- Cl)RhCp*][PF6](Cp* = η5-C5Summary:Reaction of [Cp*RhCl2]2 (1) with (LiNH)2C10H6-2,3 gives the mononuclear species Cp*Rh(NH)2C10H6-2,3 (3), which is selectively converted to the amido-bridged dinuclear Rh(III) complex [Cp*Rh{μ2-(NH)2C10H6- 2,3}(μ2-Cl)RhCp*]PF6 (4; Cp* = η5-C5Me5) upon treatment with 1/AgPF6 in acetone. The molecular structure of 4 has been determined by X-ray crystallography.
  • Synthesis and Crystal Structure of a One-Dimensional Copper(I) Polymer Containing a Bis-Bidentate Tetrathioether Ligand, T. Okubo, M. Kondo, S. Kitagawa, H. Matsuzaka, Synthetic Metals, Synthetic Metals, 102, 1464 - 1465, Aug. 1999 , Refereed
  • Novel extended linear structure of decavanadate anions linked by bis(4-pyridinium) disulfide (H(2)dpds), {(H(2)dpds)(2)[V10O26(OH)(2)]center dot 10H(2)O}(n), M Kondo, K Fujimoto, T Okubo, A Asami, S Noro, S Kitagawa, T Ishii, H Matsuzaka, CHEMISTRY LETTERS, CHEMISTRY LETTERS, (4), 291 - 292, Apr. 1999 , Refereed
    Summary:New porous coordination polymer, {(H(2)dpds)(2)[V10O26(OH)(2)] . 10H(2)O}(n) (H(2)dpds = bis(4-pyridinium) disulfide), was synthesized and structurally characterized. X-ray analysis demonstrates that the decavanadate anions are doubly bridged by H(2)dpds ligands to provide a one-dimensional structure. This network affords channeling cavities with dimension of about 2 x 4 Angstrom along the c-axis.
  • A new anion-trapping radical host, [(Cu-dppe)(3){hat-(CN)(6)}](2+), T Okubo, S Kitagawa, M Kondo, H Matsuzaka, T Ishii, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 38(7), 931 - 933, 1999 , Refereed
  • An Oxalate-Linked Copper(II) Coordination Polymer, [Cu2(oxalate)2(pyrazine)3]n, Constructed with Two Different Copper Units: X-ray Crystallographic and Electronic Structures, Susumu Kitagawa, Takashi Okubo, Satoshi Kawata, Mitsuru Kondo, Motomi Katada, Hisayoshi Kobayashi, Inorg. Chem., Inorg. Chem., 34, 4790 - 4796, 1995 , Refereed
  • Variety of spin transition temperatures of iron(II) spin crossover complexes with halogen substituted Schiff-base ligands, Hqsal(X) (X = F, Cl, Br, and I), Takayoshi Kuroda-Sowa, Rina Isobe, Norifumi Yamao, Tomohiro Fukumasu, Takashi Okubo, Masahiko Maekawa, POLYHEDRON, POLYHEDRON, 136, 74 - 78, Nov. 2017 , Refereed
    Summary:The preparation and magnetic properties of four Fe(11) Schiff-base complexes, [Fe(qsal(x))(2)] (Hqsal(x) = N-(8'-quinoly1)-2-hydroxy-5-halogeno-l-salicylaldimine; X = F(1), C1(2), Br(3), 1(4)) are reported. X-ray single crystal structure analyses of 1 and 2 reveal that Fe(II) ions in both complexes are coordinated by two qsalx ligands in meridional fashion. Molecular packing of 1 shows that a non-planar qsal(F) ligand interacts with neighboring two qsal(F) ligand's through pi-pi interactions, while that of 2 shows that two planar qsal(cl) ligands interact each other through pi-pi interaction. Although the magnetic property of 1 shows a high spin state at all the temperature range measured, the chi T-T plots of 2, 3, and 4 show gradual spin crossover behaviors with T1/2 of 308 K, 341 K, and 340 K, respectively. (C) 2017 Elsevier Ltd. All rights reserved.
  • Structural diversity of copper(I) cyclodiene complexes bridged by 3,6-bis (2-pyridyl)-1,2,4,5-tetrazine, Masahiko Maekawa, Kunihisa Sugimoto, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, INORGANICA CHIMICA ACTA, INORGANICA CHIMICA ACTA, 467, 204 - 211, Oct. 2017 , Refereed
    Summary:The reactions of CuX2 center dot nH(2)O (X = ClO4, BF4), Cu turnings and 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz) with excess 1,5-cyclooctadiene (cod) in Me2CO under C2H4 afforded dinuclear Cu(I)-bptz/eta(2), eta(2)-cod-X complexes {(1) and (4)} and dinuclear Cu(I)-2,5-H(2)bptz/eta(2), eta(2)-cod-X complexes {(2) and (5)}. In complexes 1 and 4, each Cu(I) atom is coordinated by two chelate N atoms of bptz and two C=C bonds of eta(2), eta(2)-cod in the distorted tetrahedral geometry to produce a transoid dinuclear structure. It should be noted that the redox state of the central tetrazine ring is electrochemically neutral. In complexes 2 and 5, each Cu(I) atom is coordinated by two chelate N atoms of 2,5-H(2)bptz and two C=C bonds of eta(2), eta(2)-cod in the distorted tetrahedral geometry to afford a transoid dinuclear structure in the 2,5-dihydro form. In contrast, the reactions of Cu(BF4)(2)center dot nH(2)O, Cu turnings and bptz with excess 2,5-norbornadiene (nbd) in MeEtCO under C2H4 afforded Cu(I)-2,5-H(2)bptz/eta(2)-nbd-BF4 complex (6). Each Cu(I) atom is coordinated by two chelate N atoms in bptz and one C=C bond in eta(2)-nbd to form a transoid dinuclear structure in the 2,5-dihydro form. These facts show that the flexible cod can preferentially produce a Cu(I)cyclodiene complex in the eta(2), eta(2)-mode (complexes 1, 2, 4 and 5) while the rigid nbd can produce a Cu (I)-cyclodiene complex in the eta(2)-mode (complex 6). Furthermore, the reaction of Cu(NO3) center dot 3H(2)O, Cu turnings and bptz with excess nbd in Me2CO under C2H4 afforded tetranuclear Cu(I)-4,5-H(2)bptz-NO3 complex (7) containing a unique anionic [Cu-2(nbd)(NO3)(4)](2) moiety. In the cationic [Cu-4(4,5H(2)bptz) 4] 4+ moiety, four Cu(I) atoms are bridged by four 4,5-H(2)bptz ligands to form a [4 x 4] grid-like tetranuclear structure with two 4,5-H(2)bptz ligands lying above the Cu4 mean plane and two lying below. In the anionic [Cu-2(nbd)(NO3)(4)](2) moiety, the two Cu atoms are bridged by one nbd ligand in the mu(2)-eta(2), eta(2)-mode. (C) 2017 Elsevier B. V. All rights reserved.
  • Rapid Removal and Mineralization of Bisphenol A by Heterosupramolecular Plasmonic Photocatalyst Consisting of Gold Nanoparticle-Loaded Titanium(IV) Oxide and Surfactant Admicelle, Shin-ichi Naya, Junpei Yamauchi, Takashi Okubo, Hiroaki Tada, LANGMUIR, LANGMUIR, 33(40), 10468 - 10472, Oct. 2017 , Refereed
    Summary:The establishment of technology for rapid and complete removal and mineralization of harmful phenolic compounds from water is of great importance for environmental conservation. Visible-light irradiation (lambda > 430 nm, light intensity integrated from 420 to 485 nm = 6.0 mW cm(-2)) of Au nanoparticle (NP)-loaded TiO2 (Au/TiO2) in dilute aqueous solutions of bisphenol A (BPA) and p-cresol (PC) causes degradation of the phenols. The addition of trimethylstearylammonium chloride (C(18)TAC) enhances the adsorption of BPA on Au/TiO2 to greatly increase the rate of reaction. Consequently, 10 mu M phenols are completely removed from the solutions within 2.5 h irradiation, and prolonging irradiation time to 24 h quantitatively oxidizes BPA to CO2. Dynamic light scattering zeta-potential measurements indicate that a C(18)TAC bilayer or admicelle is formed on the Au/TiO2 particle surface at C(18)TAC concentration >50 mu M. The action spectrum for reaction shows that this reaction is driven by the Au NP localized surface plasmon resonance excitation-induced interfacial electron transfer from Au to TiO2. We propose a possible reaction scheme on the basis of the experimental results including intermediate analysis.
  • Structurally Diverse Polynuclear Copper(I) Complexes Bridged by Pyrimidine-, Pyrazine-, and Triazine-based Ligands with Several 2-Pyridyl Groups, Masahiko Maekawa, Kunihisa Sugimoto, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, CHEMISTRYSELECT, CHEMISTRYSELECT, 1(13), 3812 - 3822, Aug. 2016 , Refereed
    Summary:The reactions of [Cu(MeCN)(4)]BF4 or [Cu(C2H4)(n)]ClO4 complexes with 4,6-bis(2-pyridyl)pyrimidine (bppym) in Me2CO under C2H4 afforded dinuclear Cu(I)-bppym/C2H4 adducts [Cu-2-(bppym)(C2H4)2](BF4)(2)center dot Me2CO (1) and [Cu-2(bppym)(2)(C2H4)(2)](ClO4)(2)center dot Me2CO (2), respectively. One Cu(I) atom is coordinated by bppym and C2H4 in a distorted trigonal-planar geometry. The other Cu(I) atom is coordinated by bppym, Me2CO, and C2H4 toward a distorted tetrahedral geometry. The reaction of [Cu(MeCN)(4)]BF4 with 2,3-bis(2-pyridyl)pyrazine (bppz) in MeOH under C2H4 afforded a Cu(I)-bppz coordination polymer {[Cu-2(bppz)(2)](BF4)(2)center dot MeOH} n (3). Two Cu(I) atoms are alternately bridged by two bppz to form a 1-D zigzag-chain structure. Each Cu(I) coordination sphere is largely distorted from a normal tetrahedral structure toward a square planar structure. The reaction of [Cu(MeCN)(4)]PF6 with 2,4,6-tris(2-pyridyl)-s-triazine (tptz) in MeEtCO under C2H4 afforded a tetranuclear Cu(I)-tptz/C2H4 adduct [Cu-4(tptz)(2)(C2H4)(2)(MeCN)(2)](PF6)(4)center dot MeEtCO (4b). Two Cu(I) atoms are bridged by the central triazine ring, the 2-pyridyl group, the central triazine ring, and the 2-pyridyl group in a different tptz to form a double helical structure. The other Cu(I) atom is coordinated by the central triazine ring, the 2-pyridyl group, MeCN, and C2H4 in a distorted tetrahedral geometry. The reaction of [Cu(MeCN)(4)]PF6 with tetra-2-pyridylpyrazine (tppz) in MeOH under C2H4 afforded a tetranuclear Cu(I)-tppz complex [Cu-4(tppz)(2)(MeCN)(4)](PF6)(4)center dot MeOH (5a). Each Cu(I) atom is coordinated by the central pyrazine ring, the 2-pyridyl group, the 2-pyridyl group in a different tppz, and MeCN in a distorted tetrahedral geometry. These four Cu(I) atoms are bridged by the two opposite tppz ligands to form a unique tetranuclear Cu(I) cage structure.
  • Heterometallic Ag-I-Ir-III Hydride Coordination Polymers Bridged by Ir-III Metalloligands, Masahiko Maekawa, Yukimi Kubo, Kunihisa Sugimoto, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, (1), 78 - 91, Jan. 2016 , Refereed
    Summary:A new type of Ir-III metalloligands containing an unsaturated nitrogen coordination site, [Ir(H)(2)(PPh3)(2)(pprd)]BF(4)2CHCl(3) (1), [Ir(H)(2)(PPh3)(2)(Me(2)bpm)]BF4CHCl3 (2), {[Ir(H)(2)(PPh3)(2)(Me(2)bpm)]PF6CHCl3}(4) (3), [Ir(H)(2)(PPh3)(2)(biqz)]BF(4)2CHCl(3) (4), and [Ir(H)(2)(PPh3)(2)(biqz)]PF6 (5), have been prepared by reaction of [Ir(H)(2)(PPh3)(2)(Me2CO)(2)]X (X = BF4 or PF6) with 4-(2-pyridyl)pyrimidine (pprd), 6,6-dimethyl-4,4-bipyrimidine (Me(2)bpm), or 4,4-biquinazoline (biqz). Subsequently, three novel heterometallic Ag-I-Ir-III hydride coordination polymers, {[Ir(H)(2)(-pprd)(PPh3)(2)Ag(-CF3COO)]BF4Me2CO}(n) (6), {[Ir(H)(2)(-biqz)(PPh3)(2)Ag-2(-CF3COO)(3)]Me2CO}(n) (7), and {[Ir(H)(2)(-Me(2)bpm)(PPh3)(2)Ag-2(-CF3COO)(2)]PF(6)2Me(2)CO}(n) (8) have been constructed by reaction of the Ir-III metalloligands 1, 3, and 5 with AgCF3COO. In coordination polymer 6, the [Ir(H)(2)(PPh3)(2)(pprd)](3+) units are linked through the Ag-I atoms to form a 1D zigzag chain structure. In coordination polymer 7, the dinuclear [Ag-2(-CF3COO)(3)](-) units are linked through the terminal N atoms of biqz in two different [Ir(H)(2)(PPh3)(2)(biqz)](3+) units to form a 1D zigzag chain structure. In coordination polymer 8, the [Ag-2(-CF3COO)(2)] frameworks are linked through the terminal N atoms of Me(2)bpm and the Ir-III atom in two different [Ir(H)(2)(PPh3)(2)(Me(2)bpm)](3+) units to form a waved rectangular cavity. These waved rectangular cavities are connected to each other to afford a unique 2D sheet structure.
  • Synthesis, Crystal Structure, and Electroconducting Properties of a 1D Mixed-Valence Cu(I)-Cu(II) Coordination Polymer with a Dicyclohexyl Dithiocarbamate Ligand, Kenji Nakatani, Kento Himoto, Yuki Kono, Yuuki Nakahashi, Haruho Anma, Takashi Okubo, Masahiko Maekawa, Takayoshi Kuroda-Sowa, CRYSTALS, CRYSTALS, 5(2), 215 - 225, Jun. 2015 , Refereed
  • Dinuclear and polymeric copper(I) ethylene adducts bridged by bis-pyridyl derivatives of 1,2,4-triazole and 1,2,4,5-tetrazine, Masahiko Maekawa, Kunihisa Sugimoto, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, INORGANICA CHIMICA ACTA, INORGANICA CHIMICA ACTA, 426, 64 - 70, Feb. 2015 , Refereed
    Summary:The reaction of [Cu(MeCN)(4)]PF6 with 3,5-bis(2-pyridyl)-1H-1,2,4-triazole (Hbptrz) in MeOH under C2H4 afforded the colorless needle crystals of [Cu-2(bptrz)(C2H4)(2)]PF6 center dot MeOH (1). The X-ray crystallographic study showed that there are two [Cu-2(bptrz)(C2H4)(2)](+) cation moieties, two PF6 anions and two solvated MeOH molecules in the unit cell. This result indicates that the central triazole ring was deprotonated to produce the anionic bptrz ligand. Each Cu(I) atom is coordinated by two chelate N atoms of bptrz and the C=C bond of C2H4 in the trigonal-planar geometry to produce a notable dinuclear Cu(I)-bptrz/C2H4 adduct bearing the anionic bptrz in the transoid conformation. In contrast, the reaction of Cu(NO3)(2)center dot H2O, Cu turnings and 3,6-bis(4-pyridyl)-1,2,4,5-tetrazine (4-bptz) in Me2CO under C2H4 gave black brick crystals of {[Cu-4(4,5-H-2-4-bptz)(2)(C2H4)(2)(NO3)(4)]center dot Me2CO center dot 0.5H(2)O}(n) (2). This result indicates that 3,6-bis(4-pyridyl)-4,5-dihydro-1,2,4,5-tetrazine (4,5-H-2-4-bptz) was produced by the two-electron reduction of 4-bptz. Four Cu(I) atoms are bridged by two 4,5-H-2-4-bptz and four NO3 anions to form two distinct rectangular [Cu-4(4,5-H-2-4-bptz)(2)(NO3) 4] frameworks. Furthermore, these rectangular [Cu-4(4,5-H-2-4-bptz)(2)(NO3)(4)] subunits are linked via the N atom in the central 4,5-dihydrotetrazine ring each other to generate a unique 2-D Cu(I)-4,5-H-2-4-bptz/C2H4-NO3 coordination polymer with a channel structure along the a-axis. Thermogravimetric analysis (TG-DTA) showed that complexes 1 and 2 were thermochemically stable to a relatively high temperature. (C) 2014 Elsevier B.V. All rights reserved.
  • Glass formation via structural fragmentation of a 2D coordination network, D. Umeyama, N. P. Funnell, M. J. Cliffe, J. A. Hill, A. L. Goodwin, Y. Hijikata, T. Itakura, T. Okubo, S. Horike, S. Kitagawa, CHEMICAL COMMUNICATIONS, CHEMICAL COMMUNICATIONS, 51(64), 12728 - 12731, 2015 , Refereed
    Summary:The structure of a glass obtained by the melt quenching of a two-dimensional (2D) coordination network was examined. X-ray analyses disclosed a 2D-to-0D structural transformation before and after glass formation. The mechanism is unique to coordination compounds, as it is characterized by labile and flexible coordination bonds.
  • Crystal Structure and Characterization of Trinuclear Cobalt(III) Complex with 2,3,6,7,10,11-Hexahydroxytriphenylene, Yusaku Suenaga, Honami Inada, Masataka Inomata, Ryotaro Yamaguchi, Takashi Okubo, Masahiko Maekawa, Takayoshi Kuroda-Sowa, CHEMISTRY LETTERS, CHEMISTRY LETTERS, 43(4), 562 - 564, Apr. 2014 , Refereed
    Summary:Trinuclear Co(III) complex [Co-3(III)(tpa)(3)(L)](BF4)(4) (tpa: tris-(2-pyridylmethyl)amine, H6L: 2,3,6,7,10,11-hexahydroxytriphenylene) is prepared from methanol solution. Single-crystal structure analysis revealed that the valency of the three cobalt ions is +3 and that the tris(dioxolene) bridging ligand is formally in the -5 [cat,cat,sq] oxidation state. This complex is stable in the entire temperature range investigated. Various-temperature magnetic susceptibility data for the compound displayed little variation in the range 2-300K, and the reason caused the distinct charge distribution on Co-L (L: bridging ligand) by the natural rigidity of the tripodal ligands. Also, its CH3CN solution exhibits a very strong NIR absorption arising from an internal ligand transition within the triphenylene ligand. Cyclic voltammetry (CV) measurements in CH3CN solution show three reversible cat sq redox waves for the triphenylene ligand.
  • The first copper(I) coordination polymers self-assembled by 4,4 '-biquinazoline, Masahiko Maekawa, Ai Minamino, Kunihisa Sugimoto, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, INORGANICA CHIMICA ACTA, INORGANICA CHIMICA ACTA, 414, 257 - 263, Apr. 2014 , Refereed
    Summary:The reactions of [Cu(MeCN)(4)](X) (X = BF4 or PF6) with 4,4'-biquinazoline (biqz) in MeOH under C2H4 afforded brown plate crystals of {[Cu-4(biqz)(2)(MeCN)(4)(MeOH)(4)](BF4)(4)}(n) (1) and orange prismatic crystals of {[Cu-4(biqz)(2)(MeCN)(8)](PF6)(4)}(n) (2), respectively. In both of complexes 1 and 2, two Cu(I) atoms are bridged by two biqz ligands to form a 14-membered Cu4C6N4 framework. Furthermore, the Cu4C6N4 frameworks are linked by the two chelate and bridging sites of biqz to generate a 1-D double-chain Cu(I) coordination polymer. It should be noted that two N atoms in the chelate site of the biqz ligand does not act as a normal bidentate chelate mode but form a bridge between two Cu atoms in an unidentate bridging mode. In contrast, the reaction of [Cu(C2H4)(n)]ClO4 with biqz in Me2CO under C2H4 afforded orange plate crystals of polymeric Cu(I)-biqz/C2H4 adduct {[Cu-2(biqz)(C2H4)(2)](ClO4)(2)center dot Me2CO}(n) (3). The Cu atom is coordinated by two N atoms of biqz in the chelate site and the C=C bond of C2H4 in a rather distorted trigonal-planar geometry. The other Cu atom is coordinated by two N atom of two biqz ligands in the exo bridging site and the C=C bond of C2H4 in a trigonal-planar geometry to form a 1-D zigzag-chain structure. It was proved that the Cu(I) coordination polymers bridged by the biqz ligand in the different coordination modes can be preferentially produced by the choices of the precursor Cu(I) complexes. The thermogravimetric analysis (TG-DTA) measurements showed that Cu(I)-biqz-{BF4, PF6} complexes 1 and 2 were thermochemically stable to a relatively high temperature (330-340 degrees C). (C) 2014 Elsevier B. V. All rights reserved.
  • New one-dimensional mixed-valence coordination polymers including an iodine-bridged pentanuclear copper(I) cluster unit, Takashi Okubo, Haruho Anma, Yuuki Nakahashi, Masahiko Maekawa, Takayoshi Kuroda-Sowa, POLYHEDRON, POLYHEDRON, 69, 103 - 109, Feb. 2014 , Refereed
    Summary:New mixed-valence coordination polymers {[(Cu5CuI5L2)-Cu-I-I-II(C2H5CN)(2)]center dot CHCl3)(n) (L = piperidinedithiocarbamate and hexamethyl-dithiocarbamate) with isomorphous infinite one-dimensional (1D) structures were prepared and structurally characterized via X-ray diffraction. These complexes comprised a mononuclear Cu(II) unit, (CuL2)-L-II, and a pentanuclear Cu(I) cluster unit, (Cu5I5)-I-I(C2H5CN)(2). Impedance measurements demonstrated that these Cu(I)-Cu(II) mixed-valence 1D coordination polymers displayed semiconducting behavior with low conductivities. (C) 2013 Elsevier Ltd. All rights reserved.
  • Preparations and structural diversity of copper(I) ethylene adducts with related 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine ligands, Masahiko Maekawa, Takeshi Miyazaki, Kunihisa Sugimoto, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, Susumu Kitagawa, INORGANICA CHIMICA ACTA, INORGANICA CHIMICA ACTA, 410, 46 - 53, Jan. 2014 , Refereed
    Summary:The reaction of [Cu(C2H4)n]NO3, Cu turnings, 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz), and ferrocene in Me2CO under C2H4 afforded black crystals of [Cu-4(4,5-H(2)bptz)(4)][Cu(C2H4)(NO3)(2)](2)(NO3)(2)center dot 2Me(2)CO (7). In the [Cu-4(4,5-H(2)bptz)(4)](4+) cation moiety, four Cu(I) atoms are bridged by four 4,5-H(2)bptz ligands to form a [4 x 4] grid-like tetranuclear structure. In the [Cu(C2H4)(NO3)(2)] anion moiety, the Cu atom is coordinated by two NO3 anions in the unidentate coordination mode and by the C=C bond of C2H4 to form a mononuclear Cu(I)-C2H4 adduct in the trigonal-planar geometry. It should be noted that two anionic Cu(I)-C2H4 adducts [Cu(C2H4)(NO3)(2)] are present as a co-crystal. The similar reaction of Cu(BF4)(2)center dot H2O, Cu turnings, bptz, and ferrocene in MeEtCO under C2H4 afforded colorless crystals of [Cu-2(bpdpyz)(C2H4) (2)](BF4)(2) (9). In the [Cu-2(bpdpyz)(C2H4)(2)](2+) cation moiety, each Cu(I) atom is coordinated by two chelate N atoms of bpdpyz and the C=C bond of C2H4 to afford an unusual cisoid dinuclear structure. This result shows that 3,6-bis(2-pyridyl)-4,5-dihydropyridazine (bpdpyz) can be produced by the cycloaddition of bptz with C2H4 via a Diels-Alder addition and retro-Diels-Alder elimination of dinitrogen to form complex 9. In contrast, the reaction of Cu(BF4)(2)center dot H2O, Cu turnings, and bptz in Me2CO in the absence of ferrocene afforded black crystals of [Cu-4(4,5-H(2)bptz)(4)](BF4)(4)center dot Me2CO (12). Although the apparent structure of the [Cu-4(4,5-H(2)bptz)(4)](4+) cation moiety is similar to that of the [Cu-4(4,5-H(2)bptz)(4)](4+) cation moiety in complex 7, the shape of the Cu-4 framework is closer to a square structure, resulting in the adjacency of the two opposite tetrazine rings. The preparations and structural diversity of Cu(I)-C2H4 adducts with the related bptz ligands are described in addition to related previous results. (C) 2013 Elsevier B.V. All rights reserved.
  • Crystal structure and carrier transport properties of a new semiconducting 2D coordination polymer with a 3,5-dimethylpiperidine dithiocarbamate ligand, Takashi Okubo, Haruho Anma, Naoya Tanaka, Kento Himoto, Shu Seki, Akinori Saeki, Masahiko Maekawa, Takayoshi Kuroda-Sowa, CHEMICAL COMMUNICATIONS, CHEMICAL COMMUNICATIONS, 49(39), 4316 - 4318, 2013 , Refereed
    Summary:A novel mixed-valence Cu(I)-Cu(II) coordination polymer with an infinite two-dimensional structure, [(Cu3CuBr3)-Cu-I-Br-II(3,5-Dmpip-dtc)(2)](n) (3,5-Dmpip-dtc(-) = 3,5-dimethylpiperidine dithiocarbamate), was prepared, and its structure was characterized by X-ray diffraction. It shows semiconducting behavior with a relatively small activation energy and high carrier mobility, which were investigated using impedance spectroscopy and flash photolysis time-resolved microwave conductivity measurements, respectively.
  • Structural diversity among copper(I) ethylene adducts of 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine, Masahiko Maekawa, Takeshi Miyazaki, Kunihisa Sugimoto, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, Susumu Kitagawa, DALTON TRANSACTIONS, DALTON TRANSACTIONS, 42(12), 4258 - 4266, 2013 , Refereed
    Summary:The reaction of Cu(ClO4)center dot 6H(2)O, Cu turnings, and 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz) in Me2CO under C2H4 afforded brownish-red needle crystals of {[Cu-2(bptz(center dot-))(C2H4)(2)](ClO4)}(2) (1) as a minor product and brown plate crystals of [Cu-2(2,5-H(2)bptz)(C2H4)(2)](ClO4)(2)center dot 2Me(2)CO (2). The X-ray crystallographic study showed that complex 1 is composed of two independent [Cu-2(bptz(center dot-))(C2H4)(2)](+) cation moieties and two ClO4- anions. In both of the cation moieties, each Cu(I) atom is coordinated by two chelate N atoms of bptz(center dot-) and the C=C bond of C2H4 in the trigonal-planar geometry to form a unique transoid dinuclear Cu(I)-bptz(center dot-)/C2H4 adduct bearing a metal-stabilized tetrazine anion radical, bptz(center dot-), which was produced by the one-electron reduction of bptz. In contrast, complex 2 consists of one [Cu-2(2,5-H(2)bptz)(C2H4)(2)](2+) cation moiety, two ClO4- anions, and two solvated Me2CO molecules. Each Cu(I) atom is coordinated by two chelate N atoms of 2,5-H(2)bptz and the C=C bond of C2H4 in the trigonal-planar geometry to afford a transoid dinuclear Cu(I)-C2H4 adduct with 2,5-H(2)bptz, which was produced by the two-electron reduction of bptz. Additionally, the similar reaction of Cu(ClO4)center dot 6H(2)O, Cu turnings, and bptz in Me2CO or MeEtCO under C2H4 in the presence of ferrocene afforded orange brick crystals of [Cu-2(bpdpyz)(C2H4)(2)]- (ClO4)(2)center dot Me2CO (3) and [Cu-2(bpdpyz)(C2H4)(2)](ClO4)(2) (4), respectively, together with complex 1 in higher yield. This result shows that 3,6-bis(2-pyridyl)-4,5-dihydropyridazine (bpdpyz) was produced by the cyclo-addition of bptz with C2H4 via a Diels-Alder addition and retro-Diels-Alder elimination of dinitrogen. In complexes 3 and 4, each Cu(I) atom is coordinated by two chelate N atoms of bpdpyz and the C=C bond of C2H4 to afford an unusual cisoid dinuclear Cu(I)-C2H4 adduct. Further attempts to react excess [Cu(C2H4)(n)]ClO4 with bptz in Me2CO under C2H4 afforded black brick crystals of [Cu-4(4,5-H(2)bptz)(4)](ClO4)(4)center dot 2Me(2)CO (5) together with complex 1. Complex 5 is the first [4 x 4] grid-like tetranuclear Cu(I) complex constructed by the combination of Cu(I) ion and 4,5-H(2)bptz. The four Cu(I) atoms are spanned by four 4,5-H(2)bptz ligands, with two lying above the Cu-4 mean plane and two lying below. In contrast, the similar reaction of excess [Cu(C2H4)(n)]ClO4 with bptz in Me2CO under C2H4 in the presence of ferrocene afforded reddish-brown brick crystals of {[Cu-2(2,5-H(2)bptz)(C2H4)(2)](ClO4)(2)}(2)center dot Me2CO (6) together with complexes 1 and 5. Complex 6 is composed of two independent [Cu-2(2,5-H(2)bptz)(C2H4)(2)](2+) cation moieties, four ClO4- anions, and a solvated Me2CO molecule. It is interesting that the structures of the two [Cu-2(2,5-H(2)bptz)(C2H4)(2)](2+) cation moieties are different: one has a nearly planar structure and the other possesses a boat conformation owing to the bent central dihydrotetrazine ring.
  • Dye-sensitized Solar Cells with New One-Dimensional Halide-Bridged Cu(I)-Ni(II) Heterometal Coordination Polymers Containing Hexamethylene Dithiocarbamate Ligand, Takashi Okubo, Naoya Tanaka, Haruho Anma, Kyung Ho Kim, Masahiko Maekawa, Takayoshi Kuroda-Sowa, POLYMERS, POLYMERS, 4(3), 1613 - 1626, Sep. 2012 , Refereed
    Summary:One-dimensional (1D) halide-bridged Cu(I)-Ni(II) heterometal coordination polymers containing a hexamethylene dithiocarbamate (Hm-dtc) ligand have been synthesized and crystallographically characterized. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of the coordination polymers were estimated using UV-Vis-NIR and photoelectron spectroscopies, and it was revealed that these coordination polymers have appropriate HOMO levels for use as dye sensitizers. Direct-current electrical conductivity measurements and impedance measurements indicated that these 1D Cu(I)-Ni(II) heterometal coordination polymers were insulators (sigma(300K) < 10(-12) S cm(-1)). In addition, the coordination polymers were used as sensitizing materials in dye-sensitized solar cells (DSSCs). DSSCs with 1D Cu(I)-Ni(II) heterometal coordination polymers showed lower performances than those with 1D halide-bridged Cu(I)-Cu(II) mixed-valence coordination polymers.
  • Influence of NiO anode buffer layer prepared by solution on performance of bulk-heterojunction solar cells, Kyung Ho Kim, Chiaki Takahashi, Takashi Okubo, Yoshio Abe, Midori Kawamura, APPLIED SURFACE SCIENCE, APPLIED SURFACE SCIENCE, 258(20), 7809 - 7812, Aug. 2012 , Refereed
    Summary:We investigate the properties of NiO thin films prepared by sol-gel solution and the photovoltaic performance of bulk-heterojunction (BHJ) solar cells based on NiO thin films as anode buffer layers with various film thickness and amorphous-crystalline phase. Optoelectronic properties and surface morphology of NiO films strongly depend on the thickness and phase of the NiO. The performance of solar cells based on nanocrystaline (nc-) NiO exhibits better photovoltaic characteristics in comparison to those employing an amorphous (a-) NiO. The obtained power conversion efficiency (PCE, eta) of a solar cell with a 20-nm-thick nc-NiO is 2.24%, with a short-circuit density (J(SC)) of 7.77 mA/cm(2), open-circuit voltage (V-OC) of 0.57 V, and fill factor (FF) of 0.50. (C) 2012 Elsevier B.V. All rights reserved.
  • Syntheses, crystal structures, spectroscopic characterization and unusual thermal robustness of mono- and di-nuclear Iridium(III) hydride complexes of 2,2 '-bipyrimidine, Masahiko Maekawa, Yukimi Kubo, Kunihisa Sugimoto, Toshie Minematsu, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, POLYHEDRON, POLYHEDRON, 40(1), 145 - 152, Jun. 2012 , Refereed
    Summary:The reaction of [Ir(H)(2)(PPh3)(2)(Me2CO)(2)]BF4 with 2,2'-bipyimidine (bpym) in CHCl3 afforded the yellow needle crystals of mononuclear Ir(III)-bpym/hydride complex [Ir(H)(2)(PPh3)(2)(bpym)]BF4 center dot 4CHCl(3) (1). In contrast, when CH2Cl2 or CHCl3 solution of [Ir(H)(2)(PPh3)(2)(Me2CO)(2)]BF4 were layered by the THF solution of bpym, red brick crystals of dinuclear Ir(III)-bpym/hydride complex [Ir-2(H)(4)(PPh3)(4)(bpym)](BF4)(2)center dot 2CH(2)Cl(2)center dot 2THF (2) and orange brick crystals of [Ir-2(H)(4)(PPh3)(4)(bpyrn))(BF4)(2)center dot 2CHCl(3) (3) were solvent-selectively formed. The UV-Vis spectra of complexes 1-3 in the solid state demonstrated that the absorptions of complexes 2 (495 nm) and 3 (510 nm) exhibited a significant red-shift relative to that (420 nm) of complex 1. Complexes 1-3 redissolved in CD2Cl2 gave several well-resolved H-1 NMR signals at 23 degrees C. It is noteworthy that all H-1 NMR signals of the coordinated pyrimidine rings in complexes 1-3 were shifted to the upfield region relative to those of the metal-free bpym ligand, in which the coordination shifts (Delta delta = delta(complex) - delta(metal-free)) are {-0.12 (H-6.6'), -0.73 (H-4.4') and -0.55 (H-5.5') ppm} for complex 1, {-0.81 (H-4.4') and -0.67 (H-5.5') ppm} for complex 2, and {-0.72 (H-4.4') and -0.58 (H-5.5') ppm} for complex 3. It was proved that unusual upheld shifts can be caused by the diamagnetic anisotropic ring current effect between the adjacent bpym and phenyl groups of PPh3. Thermogravimetric analysis (TG-DTA) showed that Ir(III)-bpym/hydride complexes 1-3 were thermochemically stable to a relatively high temperature near 330 degrees C. (C) 2012 Elsevier Ltd. All rights reserved.
  • Framework dimensionality of copper(I) coordination polymers of 4,4 '- bipyrimidine controlled by anions and solvents, Masahiko Maekawa, Toshi Tominaga, Kunihisa Sugimoto, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, Susumu Kitagawa, CRYSTENGCOMM, CRYSTENGCOMM, 14(4), 1345 - 1353, 2012 , Refereed
    Summary:The reaction of [Cu(C2H4)(n)]NO3 with 4,4'-bipyrimidine (bpm) in Me2CO under C2H4 afforded a polymeric Cu(I)-bpm/C2H4 adduct [Cu-2(bpm)(C2H4)(NO3)(2)](n) (1) with an infinite 1-D zigzag chain structure. Similar reactions of [Cu(C2H4)(n)]ClO4 or [Cu(MeCN)(4)]BF4 with bpm in Me2CO under C2H4 afforded Cu(I)-bpm/C2H4 adducts {[Cu-3(bpm) (2)(C2H4) (2)](ClO4)(3)}(n) (2) and {[Cu-3(bpm)(2)(C2H4)(2)](BF4)(3)}(n) (3), respectively, which have an infinite 1-D zigzag ladder structure. It is interesting that two disordered ClO4- or BF4- anions are accommodated in the inside cavity of the ladder chains. In contrast, the reaction of [Cu(MeCN)(4)]BF4 with bpm in MeOH under C2H4 afforded a Cu(I)-bpm/C2H4 adduct {[Cu-4(bpm) (3)(C2H4) (3)(MeOH)](BF4)(4)center dot 2H(2)O center dot 3MeOH}(n) (4). Three Cu atoms are bridged by three bpm ligands to form a metallacalix[3] arene structure with three legs of C2H4. Furthermore, these metallacalix[3] arenes are linked through another Cu atom in the terminal N atom of bpm to produce a chiral 2-D sheet structure with space group P6(3). One BF4- anion is accommodated in the small triangular Cu-3 cavities, whereas three disordered BF4- anions are encapsulated in the large triangular Cu-3 cavities. In contrast to complex 4, [Cu(MeCN)(4)]BF4 was reacted with bpm in MeOH under Ar, and C2H4 gas was then bubbled into the resultant brown suspensions. The reaction solution was allowed to come to room temperature, and Cu(I)-bpm complex {[Cu-3(bpm)(3)](SiF6)(1.5)}(n) (5) was collected. The tetrahedral Cu atom is coordinated by two N atoms in the chelate site of bpm and two N atoms in the terminal sites of two other bpm ligands to form two racemic metallacalix[3] arene structures. It is noteworthy that these metallacalix[3] arenes are joined through the bpm ligands to afford a 3-D cage structure consisting of two right-handed and left-handed helix networks. One disordered SiF62- anion is accommodated in the inside cavity between two opposite metallacalix[3] arene structures. On the basis of these results, it has been concluded that BF4-, PF6-, ClO4- and SiF62- anions can serve as anion templates to self-assemble polymeric Cu(I) C2H4 adducts and a cage compound in complexes 2-5. The NO3- anion is ineffective as an anion template, as indicated by the higher coordination ability of the NO3- anion in complex 1. Additionally, solvent-dependent effects have been observed in the formation process: Me2CO can preferentially induce polymeric 1-D chain and 1-D ladder structures in complexes 1-3, whereas MeOH can produce 2-D sheet and 3-D cage structures by the linage of metallacalix[3]arene structures in complexes 4 and 5.
  • Structural controls of 2D sheet copper(I) ethylene and carbonyl coordination polymers directed by anions and solvents, Masahiko Maekawa, Toshi Tominaga, Kunihisa Sugimoto, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, Susumu Kitagawa, CRYSTENGCOMM, CRYSTENGCOMM, 14(18), 5955 - 5962, 2012 , Refereed
    Summary:The reactions of Cu(I) ion with {BF4-, ClO4-, or PF6-} anions and 6,6'-dimethyl-4,4'-bipyrimidine (Me(2)bpm) under C2H4 or CO in MeOH preferentially afforded three 2D sheet Cu(I)-Me(2)bpm/{C2H4, CO} adducts [Cu-4(Me(2)bpm)(3)(C2H4)(3)(MeCN)](BF4)(4)center dot 0.33MeOH}(n) (2), {[Cu-4(Me(2)bpm)(3)(C2H4)(3)(MeOH)(0.33)](ClO4)(4)}(n) (3), and {[Cu-4(Me(2)bpm)(3)(CO)(3)(MeCN)](PF6)(4)center dot 0.33MeCN}(n) (4), whereas the similar reaction of Cu(I) ion with a BF4- anion and Me(2)bpm under CO in MeOH gave the metallamacrocyclic tetranuclear Cu(I)-Me(2)bpm/CO adduct [Cu-4(Me(2)bpm)(4)(CO)(4)](BF4)(4)center dot 4MeOH (5). In Cu(I)-Me(2)bpm/{C2H4, CO} adducts 2-4, it should be noted that the metallacalix[3]arene structures of the [Cu-3(Me(2)bpm)(3)](3+) framework are linked through another Cu atom with MeCN (2 and 4) or MeOH (3) to produce a chiral 2D sheet structure with small Cu-3 and large Cu-9 cavities. In the small triangular Cu-3 cavities, one MeOH (2) or MeCN (4) molecule is encapsulated in complexes 2 and 4, whereas these Cu-3 cavities are empty in complex 3. In the large Cu-9 cavities, one anion (X = BF4- (2), ClO4- (3) or PF6- (4)) is surrounding by six Me groups of three Me(2)bpm on the upside and three anions (X) are functionally accommodated on the downside for complexes 2-4, respectively. In the Cu(I)-Me(2)bpm/CO adduct 5, two of the four BF4- anions are accommodated in the upper and lower cavities of the [Cu-4(Me(2)bpm)(4)] framework. We demonstrated that the metallamacrocyclic and polymeric 2D sheet Cu(I)-Me(2)bpm/{C2H4, CO} adducts can be reasonably self-assembled under the direction of anions and solvents.
  • Effects of weak interactions on spin crossover properties of iron(II) complexes with extended pi-conjugated Schiff-base ligands, Takayoshi Kuroda-Sowa, Kana Kimura, Jun Kawasaki, Takashi Okubo, Masahiko Maekawa, POLYHEDRON, POLYHEDRON, 30(18), 3189 - 3192, Nov. 2011 , Refereed
    Summary:The preparation and magnetic properties of two Fe(II) Schiff-base complexes, [Fe(qnal-12)(2)]center dot 2C(6)H(6) (1) and [Fe(Hqsalc)(2)] (2), (Hqnal-12 = N-(8'-quinolyl)-1-hydroxy-2-naphthaldimine, H(2)qsalc = 4-hydroxy-3-[(8-quinolinylimino)methyl][benzoic acid) are reported. X-ray single crystal structure analysis of 1 reveals that an Fe(II) ion is coordinated by two qnal-12 ligands in a meridional fashion. Molecular packing of 1 shows that a qnal-12 interacts with neighboring two qnal-12's through it-it interactions, which results in the formation of one-dimensional chain. Although the magnetic property of 1 shows a high-spin state at all the temperature range measured, the chi T-T plot of 2 shows abrupt spin crossover behavior with a wide hysteresis of 21 K, probably due to the hydrogen-bond network originated by carboxyl groups. (C) 2011 Elsevier Ltd. All rights reserved.
  • Synthesis and Conducting Properties of a New Mixed-valence Cu(I)-Cu(II) 1-D Coordination Polymer Bridged by Morpholine Dithiocarbamate, Kyung Ho Kim, Takashi Ueta, Takashi Okubo, Shinya Hayami, Haruho Anma, Kazuya Kato, Tetsuya Shimizu, Jyunji Fujimori, Masahiko Maekawa, Takayoshi Kuroda-Sowa, CHEMISTRY LETTERS, CHEMISTRY LETTERS, 40(10), 1184 - 1186, Oct. 2011 , Refereed
    Summary:A novel mixed-valence Cu(I)-Cu(II) coordination polymer with an infinite one-dimensional (1-D) structure, [(Cu4CuI4)-Cu-I-I-II(Mor-dtc)(2)(CH3CN)(2)](n) (Mor-dtc(-): morpholine dithiocarbamate), was prepared and structurally characterized by X-ray diffraction. This complex consists of a mononuclear copper(II) unit of [Cu-II(Mor-dtc)(2)] and a tetranuclear Cu(I) unit of [Cu4I4(CH3CN)(2)]. It also shows semiconductive behaviors with a relatively small activation energy, which was revealed by impedance analysis.
  • Intervalence Charge-Transfer System by 1D Assembly of New Mixed-Valence Octanuclear Cu-I/Cu-II/Cu-III Cluster Units, Takashi Okubo, Hiroyasu Kuwamoto, Kyung Ho Kim, Shinya Hayami, Akihito Yamano, Motoo Shiro, Masahiko Maekawa, Takayoshi Kuroda-Sowa, INORGANIC CHEMISTRY, INORGANIC CHEMISTRY, 50(7), 2708 - 2710, Apr. 2011 , Refereed
    Summary:The reaction of Cu(Hm-dtc)(2), Br-2, and CuBr2 yielded a new mixed-valence octanuclear Cu-I/Cu-II/Cu-III cluster, encapsulating a Br anion in the center of the cluster cage. The octanuclear cluster units form a 1D assemblage, which induces intervalence charge-transfer transitions from Cu-II ions to Cu-III ions between the clusters.
  • Crystal structure and carrier transport properties of a new 3D mixed-valence Cu(I)-Cu(II) coordination polymer including pyrrolidine dithiocarbamate ligand, Takashi Okubo, Naoya Tanaka, Kyung Ho Kim, Haruho Anma, Shu Seki, Akinori Saeki, Masahiko Maekawa, Takayoshi Kuroda-Sowa, DALTON TRANSACTIONS, DALTON TRANSACTIONS, 40(10), 2218 - 2224, 2011 , Refereed
    Summary:A novel mixed-valence Cu(I)-Cu(II) coordination polymer having an infinite three-dimensional (3D) structure, {[(Cu4Cu2Br4)-Cu-I-Br-II(Pyr-dtc)(4)]center dot CHCl3}(n) (1) (Pyr-dtc(-) = pyrrolidine dithiocarbamate), has been prepared and structurally characterized via X-ray diffraction. This complex consists of 1D Cu(I)-Br chains and bridging mononuclear copper(II) units of Cu-II(Pyr-dtc)(2), which form an infinite 3D network. A magnetic study indicates that this complex includes copper(II) ions exhibiting a weak antiferromagnetic interaction (theta = -0.086 K) between the unpaired electrons of the copper(II) ions present in the diamagnetic Cu(I)-Br chains. The carrier transport properties of 1 are investigated using an impedance spectroscopy technique and flash-photolysis time-resolved microwave conductivity measurement (FP-TRMC). The impedance spectroscopy reveals that this complex exhibits intriguing semiconducting properties at a small activation energy (E-a = 0.29 eV (bulk)). The sum of the mobilities of the negative and positive carriers estimated via FP-TRMC is Sigma mu similar to 0.4 cm(2) V-1 s(-1).
  • Novel 1D Cu(I) coordination polymers formed by the combination of Cu(I) halides and 4-(2-pyridyl)pyrimidine, Masahiko Maekawa, Kunihisa Sugimoto, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, POLYHEDRON, POLYHEDRON, 29(14), 2807 - 2813, Sep. 2010 , Refereed
    Summary:Three novel 1D Cu(I) coordination polymers [Cu4X4(pprd)(2)](n) (X = Cl(1), Br(2) and I(3): pprd = 4-(2-pyridyl)pyrimidine) were systematically synthesized by Cu(I) halides and the pprd ligand, and they have been characterized by X-ray, IR, and TG-DTA analyses. The molecular structure of complex 1 essentially resembles to that of complex 2. In complexes 1 and 2, four Cu(I) atoms are bridged by four Cl or Br anions to form an eight-membered Cu4X4 framework in the twist-chair form. Furthermore, the Cu4X4 frameworks are coordinated by the chelate and bridging sites of two pprd ligands to form a unique 1D two-stepped Cu(I) coordination polymer, in which two stairs are formed by the Cu4X4 core and two heteroaromatic planes of pprd. In the crystal packing structures, it is interesting that two heteroaromatic planes of pprd are stacking along the b-axis for complex 1 and the a-axis for complex 2. In contrast, four Cu(I) atoms in complex 3 are bridged by four I atoms to form a Cu4I4 stepped cubane tetramer. Additionally, the Cu4I4 stepped cubane cores are linked by the chelate and bridging sites of two pprd ligands to form an infinite 1D zigzag-chain Cu(l) coordination polymer. The thermal decomposition behaviors for Cu(I)-X/pprd complexes 1, 2 and 3 were determined by thermogravimetric analysis (TG-DTA). Although the thermal decomposition behaviors of complex 1 were unidentified, those of complexes 2 and 3 were assigned. The mass loss at the first stage of thermal decomposition for polymeric [Cu4X4(pprd)(2)](n) was identical to the formation of oligomeric [Cu4X4(pprd)] by the elimination of one pprd molecule. The mass loss at the next stage was decided to the formation of Cu4X4 by the elimination of another pprd molecule. (C) 2010 Elsevier Ltd. All rights reserved.
  • Dye-sensitized Solar Cells with Halide-bridged Mixed-valence Cu(I)-Cu(II) Coordination Polymers with Hexamethylenedithiocarbamate Ligand, Kyung Ho Kim, Takashi Okubo, Naoya Tanaka, Naoto Mimura, Masahiko Maekawa, Takayoshi Kuroda-Sowa, CHEMISTRY LETTERS, CHEMISTRY LETTERS, 39(7), 792 - 793, Jul. 2010 , Refereed
    Summary:The application of halide-bridged mixed-valence Cu(I)Cu(II) coordination polymers with hexamethylenedithiocarbamate (Hm-dtc) ligand as sensitizing materials for dye-sensitized solar cells (DSSCs) with poly(3,4-ethylenedioxythiophene) tetramethacrylate (PEDOT-TMA) counter electrode is novel. DSSCs having coordination polymers in comparison with a mononuclear Cu(Hm-dtc)(2) complex exhibited better power conversion efficiency because of the high photocurrent density.
  • Magnetic and Conducting Properties of New Halide-Bridged Mixed-Valence Cu-I-Cu-II 1D Coordination Polymers Including a Hexamethylene Dithiocarbamate Ligand, Takashi Okubo, Naoya Tanaka, Kyung Ho Kim, Hironobu Yone, Masahiko Maekawa, Takayoshi Kuroda-Sowa, INORGANIC CHEMISTRY, INORGANIC CHEMISTRY, 49(8), 3700 - 3702, Apr. 2010 , Refereed
    Summary:New mixed-valence Cu-I-Cu-II coordination polymers with one-dimensional, infinite-chain structures, [(Cu2CuX2)-Cu-I-X-II(Hm-dtc)(2)(CH3-CN)(2)](n) [Hm-dtc(-) = hexamethylene dithiocarbamate, X = Br- (1), I- (2)], have been prepared and structurally characterized by X-ray diffraction. These complexes consist of a mononuclear copper(II) unit Cu-II(Hm-dtc)(2) and dinuclear copper(I) units Cu-2(I)(CH3CN)(2)X-2. Magnetic studies have revealed that these complexes have a relatively strong antiferromagnetic interaction [J = -26.9 cm(-1) (1) and J = -22.2 cm(-1) (2)] between the unpaired electrons of the Cu-II ions through the dinuclear copper(I) halide unit of (Cu2X2)-X-I in the chain. The electrical properties of 1 and 2 are investigated using an impedance spectroscopy technique, and it is revealed that these complexes exhibit intriguing semiconducting properties with small activation energies [E-a = 0.562 eV (1) and E-a = 0.479 eV (2)].
  • Supramolecularly Engineered Aggregation of a Dipolar Dye: Vesicular and Ribbonlike Architectures, Shiki Yagai, Yujiro Nakano, Shu Seki, Atsushi Asano, Takashi Okubo, Takashi Isoshima, Takashi Karatsu, Akihide Kitamura, Yoshihiro Kikkawa, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 49(51), 9990 - 9994, 2010 , Refereed
  • Novel Cu-I Ethylene Complexes with 6,6 '-Diphenyl-4,4 '-bipyrimidine Three-Dimensionally Self-Assembled by an Intermolecular pi-pi Stacking Interaction and a C-H center dot center dot center dot N Contact, Masahiko Maekawa, Toshi Tominaga, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, (28), 4225 - 4231, Oct. 2009 , Refereed
    Summary:Four novel Cu-I-Ph(2)bpm/C2H4 adducts [Cu(Ph(2)bpm)(C2H4)]X [X = BF4 (1a, 1b), ClO4 (2) and PF6 (3); Ph(2)bpm = 6,6'-diphenyl-4,4'-bipyrimidine] were prepared and they have been characterized by X-ray, H-1 NMR, IR and TG-DTA analyses. The molecular structures of Cu-I-Ph(2)bpm/C2H4 complexes la, 1b, 2 and 3 are essentially similar: the Cu atom is coordinated by two N atoms in the chelate site of Ph(2)bpm and the C=C bond of C2H4 in the trigonal-planar geometry. Interestingly, their crystal packing structures are much different from the connection manners of an intermolecular pi-pi stacking interaction and a C-H center dot center dot center dot N contact, resulting in the self-assembly of Cu-I-C2H4 adducts with a unique three-dimensional network structure. The X-ray, H-1 NMR, IR data support the assumption that the contribution of the larger Cu-I -> C2H4 pi back-donation bonding is induced by the electron-releasing phenyl group. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
  • Columnar Structure Formed by Dimeric Fe-II Schiff Base Complex: Twisted-Overlap Salophen Platforms and Ferromagnetic Interaction, Zhong Yu, Toshiyuki Shimizu, Toshi Tominaga, Takashi Okubo, Masahiko Maekawa, Takayoshi Kuroda-Sowa, BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 82(10), 1274 - 1276, Oct. 2009 , Refereed
    Summary:Columnar assembly of dimeric Fell Schiff base complex based on twisted-overlap orientation of salophen platfonns exhibits ferromagnetic interactions at low temperature, which is ascribable to mu-phenoxy-bridged Fe ... Fe interactions and pi-pi interactions.
  • Ferromagnetic interaction in iron(II)-bis-Schiff base complexes, Atsuhiro Nabei, Takayoshi Kuroda-Sowa, Toshiyuki Shimizu, Takashi Okubo, Masahiko Maekawa, Megumu Munakata, POLYHEDRON, POLYHEDRON, 28(9-10), 1734 - 1739, Jun. 2009 , Refereed
    Summary:The preparation and magnetic properties of three Fe(II)-bis-Schiff base complexes, [Fe(2)(L1)2(4,4'-bpy)]center dot MeOH (1), [Fe(L2)(EtOH)] (2) and [Fe(L3)(MeOH)] (3) (L1 =N,N'-bis(2-hydroxy-1-naphthaldehyde)-1,2-phenylenediimine; L2 = N,N'-bis(salicylidene)-1,2-phenylenediamine; L3 = N,N'-bis(5-Cl-salicylidene)-1,2-phenylenediamine; 4,4'-bpy = 4,4'-bipyridine) are reported. X-ray single crystal structure analyses for 1-3 reveal that 1 shows a dinuclear Fe(II)-bis-Schiff base complex bridged by 4,4'-bpy, while 2 and 3 show mononuclear structures. Molecular packing of 2 shows a uniform one-dimensional chain structure through hydrogen bonds and Fe center dot center dot center dot pi interaction and that of 3 indicates significant pi-pi interaction to form a dimmer structure. The chi T-T plots of 1-3 show all ferromagnetic interaction at low temperature. The origin of the ferromagnetic interaction observed in 2 is tentatively ascribed to the dimer formation through Fe center dot center dot center dot pi interaction at low temperature. (C) 2008 Elsevier Ltd. All rights reserved.
  • Effects of Metal Doping on the Spin-Crossover Properties of an Iron(II) Complex with Extended pi-Conjugated Schiff-Base Ligand Having an N4O2 Donor Set, Zhong Yu, Takayoshi Kuroda-Sowa, Hiroaki Kume, Takashi Okubo, Masahiko Maekawa, Megumu Munakata, BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 82(3), 333 - 337, Mar. 2009 , Refereed
    Summary:The spin-crossover (SCO) complex [Fe(qnal)(2)]center dot CH2Cl2 (1), (Hqnal: N-(8'-quinolyl)-2-hydroxy-1-naphthaldimine) with an N4O2 donor set, has been synthesized and characterized. Investigation of magnetic properties shows that the complex exhibits an abrupt and complete spin transition with a 5 K wide thermal hysteresis loop. The X-ray diffraction analysis of complex 1 reveals that the molecules are connected into a quasi one-dimensional chain through extended pi-pi interactions between aromatic rings of ligands. The effects of metal doping on SCO properties have been investigated in the mixed-metal system [Fe1-xMx(qnal)(2)]center dot CH2Cl2 (M = zinc(II) and nickel(II)). The results reveal that metal doping increases the gradual character of spin transition, and no marked differences found between zinc and nickel doping, which suggest the dominant effect of the doping-degree (concentration) rather than metal species on cooperativity. However, the metal doping shows different effects on critical temperature (T-1/2), where a more pronounced descending of T-1/2 is observed in response to increased Zn-doping than in Ni-doping, indicating the noticeable consequence of internal pressure due to the different radii of doping metal ions.
  • {6,6 '-Dimethoxy-2,2 '-[naphthalene-2,3-diylbis(nitrilomethylidyne)]diphenolato}thiocyanatocobalt(III) diethyl ether dichloromethane solvate, Zhong Yu, Takayoshi Kuroda-Sowa, Atsuhiro Nabei, Masahiko Maekawa, Takashi Okubo, ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE, ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE, 65(Pt 3), M257 - U298, Mar. 2009 , Refereed
    Summary:In the title complex, [Co(C(26)H(20)N(2)O(4))(NCS)]center dot C(4)H(10)O center dot CH(2)Cl(2), the pentacoordinated Co(III) atom exhibits a distorted square-pyramidal geometry with an N,N',O,O' tetradentate Schiff base ligand in the basal plane and one thiocyanate ligand at the apical site. The diethyl ether molecule is located in a cavity provided by four O atoms of the ligand with weak C-H center dot center dot center dot O interactions, generating two short O center dot center dot center dot O contact distances [2.766 (3) and 2.745 (3) angstrom] between the diethyl ether molecule and the ligand. The crystal structure is stabilized by the weak C-H center dot center dot center dot O and C-H center dot center dot center dot N interactions and pi-pi interactions between the naphthyl ring system and the benzene ring [centroid-centroid distance = 3.657 (5) angstrom] and between the two naphthyl ring systems [centroid-centroid distance = 4.305 (2) angstrom].
  • {6,6 '-Dimethoxy-2,2 '-[o-phenylenebis(nitrilomethylidyne)]diphenolato}cobalt(II) dichloromethane disolvate, Atsuhiro Nabei, Takayoshi Kuroda-Sowa, Takashi Okubo, Masahiko Maekawa, Megumu Munakata, ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE, ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE, 65(Pt 2), M188 - U669, Feb. 2009 , Refereed
    Summary:The title compound, [Co(C(22)H(18)N(2)O(4))]center dot 2CH(2)Cl(2), was isolated from the reaction of N,N '(o-phenylene)bis(vanillalimine) (H(2)L) with Co(SCN)(2). The crystal structure contains a Co(II) ion surrounded by the L(2-) ligand in a slightly distorted square-planar fashion. Intermolecular C-H center dot center dot center dot O hydrogen-bonding contacts between the dichloromethane solvent molecules and the methoxy or carboxylate O atoms are observed in the crystal structure. The planar complex molecules stack through inversion related pi-pi interactions between the six-membered rings of the vanillalimine half ligands. The distance between centroids is 3.498 (2) angstrom and the perpendicular distance is 3.345 angstrom. A partial stacking is observed with a centroid-centroid distance of 3.830 (2) angstrom, a perpendicular distance of 3.350 angstrom and a slippage of 1.856 angstrom.
  • A unique chair-shaped hexanuclear Cu(I) metallamacrocyclic C2H4 adduct encapsulating a BF4- anion, Masahiko Maekawa, Atsuhiro Nabei, Toshi Tominaga, Kunihisa Sugimoto, Toshie Minematsu, Takashi Okubo, Takayoshi Kuroda-Sowa, Megumu Munakata, Susumu Kitagawa, DALTON TRANSACTIONS, DALTON TRANSACTIONS, (3), 415 - 417, 2009 , Refereed
    Summary:Three novel Cu(I)-C2H4 adducts bearing 4-(2-pyridyl)-pyrimidine were self-assembled, and the roles of anion and solvent were proved in the formation process.
  • The effect of molecular packing on the occurrence of spin crossover phenomena in one-dimensional Fe(II)-bis-Schiff base complexes, Atsuhiro Nabei, Takayoshi Kuroda-Sowa, Takashi Okubo, Masahiko Maekawa, Megumu Munakata, INORGANICA CHIMICA ACTA, INORGANICA CHIMICA ACTA, 361(12-13), 3489 - 3493, Sep. 2008 , Refereed
    Summary:Two new one-dimensional Fe(II)-bis-Schiff base complexes, [Fe(L1)(pyz)] center dot CH(2)Cl(2) (1) and [Fe(L2)(pyz)] center dot 2CH(2)Cl(2) (2) (H(2)L1 = bis(O-vanillin)-O-phenylenediimine, H(2)L2 = bis(O-vanillin)-2,3-naphthalenediimine, pyz = pyrazine) are reported with their crystal structures and magnetic property. Compound 1 shows a two-step SCO behavior while 2 shows HS at all the temperature range measured. Although the extension of aromatic moiety from benzene (L1) to naphthalene (L2) was introduced for the purpose of strengthening the cooperativity, it leads to the absence of SCO, due to the unanticipated pi-pi interaction, which leads to the longer Fe-N bond lengths and a weak ligand field around Fe(II) ion. (c) 2008 Elsevier B. V. All rights reserved.
  • Hysteresis loops in dielectric properties of the thermochromic copper(II) compounds, Shinya Hayami, Natsuko Motokawa, Aya Shuto, Naoji Masuhara, Yasuhiro Umebayashi, Yonezo Maeda, Osamu Sato, Katsuya Inoue, Ryo Kawajiri, Yui Kumura, Takashi Okubo, Tadaoki Mitani, CHEMISTRY LETTERS, CHEMISTRY LETTERS, 35(10), 1114 - 1115, Oct. 2006 , Refereed
    Summary:The dielectric changes of thermochromic compounds, [Cu(dieten)(2)]X-2 (X = BF4 and ClO4, dieten = NN-diethylethylenediamine), have been induced by the transformation between square-planar and distorted-square-planar.
  • Structural and magnetic studies on a new mixed-valence Cu(I)-Cu(II) octanuclear cluster with a dithiocarbarnate derivative, Ryo Kawajiri, Takashi Okubo, Tadaoki Mitani, POLYHEDRON, POLYHEDRON, 25(13), 2650 - 2654, Sep. 2006 , Refereed
    Summary:A new mixed-valence Cu(I)-Cu(II) octanuclear cluster, [(CuCuII)-Cu-I (n-Pr(2)dtc)Cl-2](2)[Cu-2(II)(n-Pr(2)dtc)(2)Cl-2](2) (1) (n-Pr(2)dtc(-) = di-n-propyldithiocarbamate) with a dithiocarbamate derivative has been synthesized and structurally characterized. Complex I consists of a mixed-valence Cu(I)-Cu(II) tetranuclear unit and two chloride-bridged Cu(II) dinuclear units. The octanuclear cluster forms an infinite one-dimensional assembly by weak Cu center dot center dot center dot Cl and Cu center dot center dot center dot S coordination bonds between the chloride bridged dinuclear units. The magnetic study indicates the existence of a strong antiferromagnetic interaction (J = -35.6 cm(-1)) between the copper ions of the chloride-bridged Cu(II) dinuclear unit, Cu-2(II) (n-Pr(2)dtc)(2)Cl-2. (C) 2006 Elsevier Ltd. All rights reserved.
  • A new honeycomb assemblage of a trisdithiolene vanadium(IV) complex, (PPh4)(2)[V(dbddto)(3)](C6H4Cl2)(hexane)(0.5), T Okubo, R Maeda, M Kondo, T Mitani, S Kitagawa, CHEMISTRY LETTERS, CHEMISTRY LETTERS, 35(1), 34 - 35, Jan. 2006
    Summary:A new trisdithiolene vanadium(IV) complex has been synthesized and characterized. The enantionieric anion units, [V(dbddto)(3)](2-), are packed so closely that the sulfur-rich planar ligands stack to form a honeycomb sheet structure, resulting, in the creation of large cavities (12 x 5.5 angstrom) for guests. The magnetic susceptibilities show ail existence of antiferromagnetic interaction in spite of the large interatomic separation of the vanadium ions (V...V distance = 11.069 angstrom (av.)), associated with the interaction between the stacking ligand pathway in the honeycomb sheet.
  • A mixed-valence coordination polymer featuring two-dimensional ferroelectric order: {[(Cu4CuII)-Cu-I(Et(2)dtc)(2)Cl-3][Cu-II(Et(2)dtc)(2)](2)(FeC4)}(n) (Et(2)dtc(-) = diethyidithiocarbamate), T Okubo, R Kawajiri, T Mitani, T Shimoda, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 127(50), 17598 - 17599, Dec. 2005 , Refereed
  • Framework control by a metalloligand having multicoordination ability: New synthetic approach for crystal structures and magnetic properties, S Noro, H Miyasaka, S Kitagawa, T Wada, T Okubo, M Yamashita, T Mitani, INORGANIC CHEMISTRY, INORGANIC CHEMISTRY, 44(1), 133 - 146, Jan. 2005 , Refereed
    Summary:By utilizing the novel metalloligand L(Cu) [Cu(2,4-pydca)(2)](2-) (2,4-pydca (2-) = pyridine-2,4-dicarboxylate), which possesses two kinds of coordination groups, selective bond formation with the series of the first-period transition metal ions (Mn(II), Fe(II), Co(II), Cu(II), and Zn(II)) has been accomplished. Depending on the coordination mode of 4-carboxylate with Co(II), Cu(II), and Zn(II) ions, L(Cu) forms a one-dimensional (1-D) assembly with a repeating motif of [-M-O(2)C-(py)N-Cu-N(py)-CO(2)-]: {[ZnL(Cu)(H(2)O)(3)(DMF)](.)DMF}(n) (2), [ZnL(Cu)(H(2)O)(2)(MeOH)(2)](n) (3), and {[ML(Cu)(H(2)O)(4)](.)2H(2)O}(n) (M = Co (4), Cu (5), Zn (6)). The use of a terminal ligand of 2,2'-bipyridine (2,2'-bpy), in addition to the Cu(II) ion, gives a zigzag 1-D assembly with the similar repeating unit as 4-6: {[Cu(2,2'-bpy)L(Cu)](.)3H(2)O}(n) (9). On the other hand, for Mn(II) and Fe(II) ions, L(Cu) shows a 2-carboxylate bridging mode to form an another 1-D assembly with a repeating motif of [-M-O-C-O-Cu-O-C-O-]: [ML(Cu)(H(2)O)(4)](n) (M = Mn (7), Fe (8)). This selectivity is related to the strength of Lewis basicity and the electrostatic effect of L(Cu) and the Irving-Williams order on the present metal ions. According to their bridging modes, a variety of magnetic properties are obtained: 4, 5, and 9, which have the 4-carboxypyridinate bridge between magnetic centers, have weak antiferromagnetic interaction, whereas 7 and 8 with the carboxylate bridge between magnetic centers reveal 1-D ferromagnetic behavior (Cu(II)-M(II); M(II) = Mn(II), J/k(B) = 0.69 K for 7; M(II) = Fe(II), J/k(B) = 0.71 K for 8).
  • Effect of the metal-assisted assembling mode on the redox states of hexaazatriphenylene hexacarbonitrile, S Furukawa, T Okubo, S Masaoka, D Tanaka, HC Chang, S Kitagawa, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 44(18), 2700 - 2704, 2005 , Refereed
  • Improved lifetime of an OLED using aluminum(III) tris (8-hydroxyquinolate), TS Kim, DH Kim, HJ Im, K Shimada, R Kawajiri, T Okubo, H Murata, T Mitani, SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS, SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS, 5(3), 331 - 337, May 2004 , Refereed
    Summary:Improved lifetime with enhanced efficiency of an Alq(3) based OLED was realized by the co-evaporation of hexamethylbenzene (HMB). Two different solvated crystalline systems of Alq3, Alq(3)(C7H8)(1/2), Alq(3)(C2H5OH), were synthesized to investigate the effect of optically inactive materials on the emission properties of Alq(3). Clathrate solvents perturb the excited electronic states of Alq(3) so that the incorporated materials in OLEDs should be chemically and optically inactive to control polymorphs. HMB acts as a carrier blocker for both electrons and holes. However, Alq(3) may be stabilized from Joule heat if the Joule heat is efficiently consumed as the vibrational/rotational energy of HMB. Consequently, the self-quenching and the crystallization of Alq(3) are effectively suppressed by the HMB, resulting in prolonged operating time and enhanced efficiency for Alq(3)-OLEDs. (C) 2004 Published by Elsevier Ltd.
  • The NOR observation of Spin-Peierls transition in an antiferromagnetic MX-chain complex [NiBr(chxn) (2)]Br-2, S Takaishi, Y Tobu, H Kitagawa, A Goto, T Shimizu, T Okubo, T Mitani, R Ikeda, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 126(6), 1614 - 1615, Feb. 2004 , Refereed
  • Synthesis, polymorphs, and luminescent properties of oligomeric Zn(3)ppo(6), TS Kim, T Okubo, T Mitani, CHEMISTRY OF MATERIALS, CHEMISTRY OF MATERIALS, 15(26), 4949 - 4955, Dec. 2003 , Refereed
    Summary:Oligomeric Zn(3)ppo(6), where ppo is 2-(2-hydroxyphenyl)-5-phenyl-1,3-oxazole, has been synthesized as a new blue-emitting material for organic light-emitting diodes (OLEDs). The electroluminescence maximum wavelength is 450 nm and the Commission Internationale de l'Eclairage (CIE) coordinates are x = 0.15, y = 0.11 for blue chromaticity. The luminance efficiency and the maximum luminance were about 1.3 lm/W at 6 V, 5.8 mA/cm(2) (139 cd/m(2)), and 8140 cd/m(2) at 11.4 V. Zn(3)ppo(6) shows two trimeric polymorphs and a monomeric structure at different sublimation temperatures.
  • Hydrogen-bonded charge-transfer complexes of TTF containing a uracil moiety: Crystal structures and electronic properties of the hydrogen cyananilate and TCNQ complexes, Y Morita, S Maki, M Ohmoto, H Kitagawa, T Okubo, T Mitani, K Nakasuji, ORGANIC LETTERS, ORGANIC LETTERS, 4(13), 2185 - 2188, Jun. 2002 , Refereed
    Summary:[GRAPHICS] A novel TTF-based donor with a uracil moiety, TTF-(1-n-butyluracil-5-yl) (TnbU), was synthesized. Crystal structures of both TnbU and the charge-transfer complex of TnbU-hydrogen cyananilate possess complementary double hydrogen bonds through uracil moieties and pi-stacking dimer structures between TTF skeletons. Furthermore, the TnbU-TCNQ charge-transfer complex shows a high electrical conductivity underlying the partial charge-transfer accompanied by a hydrogen-bonding interaction, which was substantiated in terms of the measurements of the IR, electronic spectra, and conductivity.
  • An infinite zigzag chain of the halide-bridged tetrakis(acetamidato)dirhodium cation radical, ZY Yang, M Ebihara, T Kawamura, T Okubo, T Mitani, INORGANICA CHIMICA ACTA, INORGANICA CHIMICA ACTA, 321(1-2), 97 - 106, Sep. 2001 , Refereed
    Summary:The reaction of 2,2-cis-[Rh,(acam)(4)(H2O)(2)]ClO4 (1) (Hacam = acetamide) with sodium halides in aqueous solution gave crystals of [Rh-2(acam)(4)X](n). mnH(2)O (X=Cl, Br, I). The composition of the products depended on the reaction temperature. The anhydrous compounds, [Rh-2(acam)(4)X](n) (X = Cl, 2; Br, 3; I, 4), were obtained at 40 degreesC, and the hydrated compounds, [Rh-2(acam)(4)Cl]. 7nH(2)O (2(.)7nH(2)O), [Rh-2(acam)(4)Br](n). 3nH(2)O (3(.)3nH(2)O) and [Rh-2(acam)(4)I](n). 2nH(2)O (4(.)2nH(2)O), were obtained at room temperature (15-25 degreesC. All of the compounds consist of infinite zigzag chains of (Rh-Rh-X-) units, which are supported by hydrogen bonds involving the NH(acam) and O(acam) atoms. The SOMO of the Rh-2(5+) units in the crystals can be assigned as the delta (RhRh)* MO from the Rh-L bond lengths, when compared with the corresponding Rh-2(4+) complex. The magnetic susceptibilities of 2, 3 and 4 are described by a I-D Heisenberg antiferromagnet with g = 2.003, 2.012, and 2.065, and J = - 8.6, - 7.9, and - 1.2 K, respectively. The ESR spectra of powdered crystals of 2, 3, and 4 were characteristic of rapid in-chain spin flip-flop exchange, most probably induced by the Heisenberg exchange interaction. (C) 2001 Elsevier Science B.V. All rights reserved.
  • Preparation, structure, and reactivities of amido-bridged dinuclear rhodium(III) and rhodium(II) complexes, H Matsuzaka, T Kamura, K Ariga, Y Watanabe, T Okubo, T Ishii, M Yamashita, M Kondo, S Kitagawa, ORGANOMETALLICS, ORGANOMETALLICS, 19(3), 216 - 218, Feb. 2000 , Refereed
    Summary:Reaction of [Cp*RhX(mu(2)-X)](2) (2a, X= Cl; 2b, X = Br) with (LiNH)(2)C10H6-1,8 gave the novel amido-bridged dinuclear Rh(III) complex [Cp*Rh{(mu(2)-NH)(2)C10H6- 1,8}(mu(2)-X)RhCp*]X (3a, X = Cl; 3b, X = Br), which further converted to the Rh(II) complex Cp*Rh{(mu(2)-NH)(2)C10H6-1,8}RhCp* (4) by Na/Hg reduction. Treatment of 4 with benzyl bromides produced 3b and the corresponding bz:benzyl derivatives, whereas protonation of 4 with CF3CO2H afforded [Cp*Rh{mu(2)-NH)(2)C10H6-1,8}{mu(2)-H)RhCp*]O2CCF3 (5). Complex 2a also reacted with 2 equiv of LiNHC6H4R-p to yield [Cp*Rh(mu(2)-NHC6H4R-p)(3)RhCp*]Cl (6 . Cl: 6a, R = Me; 6b, R = H; 6c, R = Cl).
  • Rational synthesis of stable channel-like cavities with methane gas adsorption properties: [{Cu-2(pzdc)(2)(L)}(n)] (pzdc = pyrazine-2,3-dicarboxylate; L = a pillar ligand), M Kondo, T Okubo, A Asami, S Noro, T Yoshitomi, S Kitagawa, T Ishii, H Matsuzaka, K Seki, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 38(1-2), 140 - 143, 1999 , Refereed
  • Synthesis, structure, and magnetic properties of one-dimensional copper(II) coordination polymer, {[Cu(pyrazine-2,3-dicarboxylate)(H2O)(2)]center dot 2H(2)O}(n), T Okubo, M Kondo, S Kitagawa, SYNTHETIC METALS, SYNTHETIC METALS, 85(1-3), 1661 - 1662, Feb. 1997 , Refereed
    Summary:A title compound has been synthesized and characterized. The complex crystallizes in the monoclinic space group C2/c with a = 12.768(1)Angstrom, b = 7.5159(8)Angstrom, c = 13.271(1)Angstrom, beta = 123.591(4)degrees, V = 1060.8(2)Angstrom(3) and Z = 4. The complex consists of one-dimensional chains of copper(II) ions bridged by pyrazine-2,3-dicarboxylate. Each copper ion has a distorted octahedral coordination with N2O4 chromophor. The magnetic susceptibility data over a range of 2 - 300 K were fitted by using an Heisenberg antiferromagnet, H = 2J Sigma S-i . Si+1, with the parameters of J = -1.40 cm(-1), g = 2.14 and rho = 0.032.
  • Synthesis, structure and magnetic properties of a two-dimensional nickel(II) coordination polymer, {[Ni(pzdc)(pyz)]center dot 2H(2)O}(n) (H(2)pzdc equals pyrazine-2,3-dicarboxylic acid; pyz equals pyrazine), T Okubo, M Kondo, S Kawata, S Kitagawa, A Miyazaki, T Enoki, MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 285, 437 - 442, 1996 , Refereed
    Summary:A title compound has been synthesized and characterized. The complex crystallizes in the orthorhombic space group Cmcm with a = 7.004(2) Angstrom, b = 12.748(2) Angstrom, c = 13.665(2) Angstrom, V = 1220.1(3) Angstrom(3) and Z = 4. The complex consists of two-dimensional square arrays of nickel(II) ions bridged by pzdc(2-) and pyz ligands. Each nickel ion has a slightly distorted octahedral coordination with N4O2 chromopher. The magnetic susceptibility data over a range of 2 - 300 K were fitted by using an Heisenberg antiferromagnet with a mean field approximation. The obtained J and zJ' values are -1.70 cm(-1) and -0.70 cm(-1), respectively.
  • Conference Activities & Talks

    • Crystal structures and carrier transport properties of coordination polymers including copper(I) halides, Takashi Okubo, China-Japan Symposium of Functional Coordination Chemistry,   2019 04 12 , 招待有り
    • Conducting Porperties and Application to Organic Solar Cells of Coordination Polymers Including Copper(I) Halides, Takashi Okubo, Advances in Organic and Hybrid Electronic Materials 2018 (AOHM19),   2019 03 17
    • Crystal Structures and Carrier Transport Properties of Coordination Polymers Including Copper(I) Halides, Takashi Okubo, 2018 Nankai International Symposium on Advanced Materials,   2018 11 13 , 招待有り
    • Conducting Properties and Application to Organic Solar Cells of Coordination Polymers Consisting of Copper(I) Halides and Hexaazatriphenylene Derivatives, T. Okubo, W. Genno, M. Okita, S. Shimakawa, K. Nakamura, K. Himoto, M. Maekawa, T. Kuroda-Sowa, International Conference on Coordination Chemistry, 2018, Sendai, Japan,   2018 08 01 , 招待有り
    • Development of bulk hetero-junction organic thin-film photovoltaic cells, Takashi OKUBO, Koki TANISHIMA, Kento HIMOTO, Toshiya HORII, Wataru Genno, Masahiko MAEKAWA, Takayoshi KURODA-SOWA, International Symposium on Chemistry for Solar Energy Applications 2017,   2017 08 31
    • First Cu(I) coordination polymers of 4,4’-biquinazoline and the C2H4 adduct, The 40th International Conference on Coordination Chemistry (ICCC40),   2012 09 , The 40th International Conference on Coordination Chemistry (ICCC40)
    • Structural controls of Cu(I) C2H4 coordination polymers of 4,4’-bipyrimidine, The 40th International Conference on Coordination Chemistry (ICCC40),   2012 09 , The 40th International Conference on Coordination Chemistry (ICCC40)
    • Novel mono- and dinuclear Iridium(III) hydride complexes of 2,2’-bipyrimidine, The 40th International Conference on Coordination Chemistry (ICCC40),   2012 09 , The 40th International Conference on Coordination Chemistry (ICCC40)
    • Novel Cu(I) metallamacrocycles toward structurally and functionally new inorganic anion receptors, The 2010 International Chemical Congress of Pacific Basin Societies (Pacifichem 2010),   2010 12 , The 2010 International Chemical Congress of Pacific Basin Societies (Pacifichem 2010)
    • Synthesis and structures of novel Cu(I) ethylene complexes with a tetrazine anion radical ring,   2010 03
    • Novel Cu(I) Ethylene Complexes Three?Dimensionally Self?Assembled by an Intermolecular π?π Stacking Interaction and a C?H???N Contact, The second Asian Conference on Coordination Chemistry (2nd ACCC),   2009 11 , The second Asian Conference on Coordination Chemistry (2nd ACCC)
    • Synthesis of Cu(I) and Ag(I) Metallamacrocycles as Structurally and Functionally New Inorganic Anion Receptors, The second Asian Conference on Coordination Chemistry (2nd ACCC),   2009 11 , The second Asian Conference on Coordination Chemistry (2nd ACCC)
    • Self-assemblies of novel Cu(I) metallamacrocyclic carbonyl adducts by anion templation,   2009 03
    • Self-assemblies of novel Cu(I) metallamacrocyclic ethylene adducts by 4,4'-bipyrimidine derivatives,   2009 03
    • Self-assemblies of novel Cu(I) and Ag(I) coordination polymers by anion templation,   2008 03
    • Synthesis and characterization of metal-organic frameworks with Mn12 SMM’s as guests,   2007 09

    Research Grants & Projects

    • JST, PRESTO, Development of Composite Interfaces Including Ferroelectric Coordination Polymers and Application to Photoelectric Conversion Devices
    • JST, PRESTO, Development of Multifunctional Mixed-Valence Metal-Assembled Complexes