Eigo Isomura

Tokyo Metropolitan University, Tokyo, Tokyo-to, Japan

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Publications (9)27.53 Total impact

  • Eigo Isomura · Tohru Nishinaga · Masahiko Iyoda
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    ABSTRACT: Amphiphilic tetrathiafulvalene (TTF) having both long alkylthio chains and pyridylethynyl groups was synthesised, and its nanostructure and redox properties were investigated. The bis(pyridylethynyl)TTF formed 1D flat and helical tapes. Since these tapes were of micrometre size, the conductivities of neutral and I2-doped tapes could be measured by directly attaching gold wires to the tape. After doping with I2, the colour of the tape changed from purple to black, and the tape behaved as a semiconductor up to 2.6 × 10− 4 S cm− 1.
    Supramolecular Chemistry 03/2011; 23(3-4-3–4):304-309. DOI:10.1080/10610278.2010.527978 · 2.39 Impact Factor
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    ABSTRACT: We synthesized 4,5-bis(octadecylthio)-4′,5′-bis(ethylcarbamoyl)tetrathiafulvalene and measured the electrical conductivity of its perchlorate (ClO4−)-doped nanofibers, which have double and triple helix structures. The nanostructure of the bis(octadecylthio)-TTF–diamide and its ClO4−-doped fibers in a 3:1 ratio was deduced in relation to the X-ray crystal structure of bis(methylthio)-TTF–diamide. The doubly coiled nanofibers form when initially formed spiral ribbons of lamellarly arranged TTF–diamide perchlorate split in the middle, and a further split of the double helix produces the triplex structure. Temperature-dependent conductance and current–voltage (I–V) characteristics of the coiled fibers were measured in the temperature (T) range of 70–300 K. The conductance decreased with a decrease in T, and the I–V characteristics were nonlinear over the entire T range. The results were analyzed by using a modified fluctuation-induced tunneling conduction model, where the barrier height and width were linearly dependent on the electric field.
    Journal of Materials Chemistry 11/2010; 20(48):10817-10823. DOI:10.1039/C0JM02628J · 7.44 Impact Factor
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    ABSTRACT: Heterotrinuclear Fe(II)-Cu(II)-Fe(II) complexes [Cu(FcTropOMe)(2)(H(2)O)(2)](OTf)(2) (FcTropOMe = 5-ferrocenyl-2-methoxytropone) (1), [Cu(FcTropNEt(2))(2)](OTf)(2) (FcTropNEt(2) = 2-(N,N-diethylamino)-5-ferrocenyltropone) (2) and [Cu(FcTropNEt)(2)] (FcTropNEt = 2-(N-ethylamino)-5-ferrocenyltroponate) (3) were synthesized. In addition, a hexafluorophosphate salt of heterotrinuclear Fe(III)-Cu(II)-Fe(III) complex [Cu(FcTropNEt)(2)](2+) (3(2+)) was successfully obtained as single crystals by electrochemical oxidation of 3. By comparing the X-ray structures and absorption spectra of dicationic complexes 1 and 2, the 2-(diethylamino)tropone ligand was found to induce a greater intramolecular charge transfer (CT) from ferrocenyl to tropone-Cu(II) moieties than the 2-methoxytropone ligand. On the other hand, 3(2+) showed a broad CT band in the near-infrared (NIR) region similar to 2, which can be assigned to a transition from troponato-Cu(II) to ferrocenium moieties. As for the magnetic properties of 3(2+)(PF(6)(-))(2), measurements of temperature dependence of magnetic susceptibility and ESR on the solid state and in solution revealed the presence of a strong ferromagnetic interaction (J(Fe-Cu) = +12.0 cm(-1)) between the low spin Fe(III) ion with S = 1/2 and Cu(II) ion with S = 1/2 despite a long distance pathway via the aminotroponato and cyclopentadienyl moieties. DFT calculations supported this intramolecular ferromagnetism, which is induced by a spin polarization mechanism through the pi-spacers.
    Dalton Transactions 03/2010; 39(9):2293-300. DOI:10.1039/b912255a · 4.20 Impact Factor
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    ABSTRACT: The FeCl3-mediated homo-coupling of 4,5-bis(alkylthio)-4′-tetrathiafulvalenylmagnesium bromide 5 produced the corresponding bitetrathiafulvalene derivatives 2a–d in moderate yields (25–51%). Bitetrathiafulvalenes 2c and 2d having long alkylthio chains formed nanostructures and showed bulk electric conductivities (σrt=2.6−8.0×10−5Scm−1) in the neutral state owing to the fastener effect. Interestingly, the nanofiber of tetrakis(dodecylthio)bitetrathiafulvalene 2d exhibited a p-type semiconductivity as detected by AFM.
    Tetrahedron Letters 01/2010; 51(4):679-682. DOI:10.1016/j.tetlet.2009.11.106 · 2.38 Impact Factor
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    ABSTRACT: Tris(tetrathiafulvaleno)dodecadehydro[18]annulene-hexaesters have a multi-functionality that is very sensitive to small differences in the ester side-chain. Self-aggregation of the [18]annulenes in amphiphilic media such as THF-H(2)O (v/v, 1:1) either produce a fibrous structure or result in temperature hysteresis of the color and (1)H NMR signals. This temperature hysteresis in solution is due to both strong self-aggregation behavior and unique cluster formation in a binary solution of THF and water.
    ChemPhysChem 10/2009; 10(15):2607-11. DOI:10.1002/cphc.200900545 · 3.42 Impact Factor
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    ABSTRACT: Synthesis of redox-active bis-pyridine ligand, 4′,5′-bis(methylthio)-4,5-bis(2-pyridylethynyl)tetrathiafulvalene (1) has been carried out in moderate yield starting from the corresponding diiodide. Bis(pyridylethynyl)–TTF 1 forms 1:1 complexes with Cu(I) and Cu(II) salts. Occurrence of the charge transfer from the TTF moiety to the copper atom was found to depend on the environment of copper atom.
    Tetrahedron Letters 08/2007; 48(33):5895-5898. DOI:10.1016/j.tetlet.2007.06.048 · 2.38 Impact Factor
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    ABSTRACT: Syntheses of all-Z-tribenzo[12]annulenes (1a–c) and Z,Z-tribenzodidehydro[12]annulenes (2a–c) by the reduction of the corresponding tribenzohexadehydro[12]annulenes 3a–c were carried out using a low valent titanium complex generated from Ti(O-i-Pr)4 and i-PrMgCl. The unique structure of the first reduction products 2a–c as well as 1a–c was fully characterized. Complexation of these annulenes with silver(I) ions produces the corresponding silver complexes. Among them, the silver complexes of 2a–c exhibit interesting monomer–dimer equilibrium.
    Tetrahedron Letters 05/2007; 48(19):3433-3436. DOI:10.1016/j.tetlet.2007.03.044 · 2.38 Impact Factor
  • Yoshihiro Miyake · Eigo Isomura · Masahiko Iyoda
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    ABSTRACT: The iridium-catalyzed hydrosilylation of alkynes in the presence of 4,4,5,5'-tetramethylbiphosphinine (tmbp) has been explored. The hydrosilylation of alkynes in the presence of tmbp proceeds effectively to give beta-(E)-vinylsilanes highly selectively in moderate to high yields, whereas a similar hydrosilylation in the absence of tmbp produces beta-(Z)-vinylsilanes selectively. The stereoselectivity of these reactions suggests the importance of the electron-withdrawing properties of tmbp coordinated to iridium.
    ChemInform 01/2007; 38(2). DOI:10.1002/chin.200702162
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    ABSTRACT: 195Pt chemical shifts and 1JPt–Pt coupling constants were measured for a series of head-to-head (HH) and head-to-tail (HT) amidato-bridged cis-diammineplatinum(III) dinuclear complexes involved in the axial water substitution reactions with halide ions (X– = Cl–, Br–): HH-[Pt2(NH3)4(μ-amidato)2L1L2]n+ ≡ [L1–Pt(N2O2)–Pt(N4)–L2]n+ (amidato = α-pyridonato, α-pyrrolidonato, and pivalamidato) and HT-[Pt2(NH3)4(μ-α-pyridonato)2L1L2]n+ ≡ [L1–Pt(N3O)–Pt(N3O)–L2]n+; the diaqua (L1, L2 = H2O, n = 4), the aquahalo (L1 = X–, L2 = H2O, n = 3), and the dihalo complexes (L1, L2 = X–, n = 2). The 195Pt NMR spectroscopic data were considered in relation to the lability in the axial ligand substitution reaction and the electron distribution along the Pt–Pt bond. The NMR spectroscopic data suggested different electron distributions along the Pt–Pt bonds in all the HH dimers and in the HT aquahalo dimers, such as [L1–PtIV(N2O2)–PtII(N4)–L2]n+ and [X–PtIV(N3O)–PtII(N3O)–OH2]3+, respectively. Relative shifts of the 195Pt NMR signals for each substitution step indicate that the replacement of the axial water ligand by X– affects more effectively the electron density of the opposite Pt atom than that of the substituted one. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
    Berichte der deutschen chemischen Gesellschaft 06/2006; 2006(12):2484 - 2490. DOI:10.1002/ejic.200500954 · 2.94 Impact Factor