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Synthesis and Properties of a Mixed-Valence Compound with Single-Step Tunneling and Multiple-Step Hopping Behavior

Authors

  • Rim Makhoul,

    1. Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
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  • Yuki Kumamoto,

    1. Department of Environmental Applied Chemistry, University of Toyama, Toyama 930-8555, Japan
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  • Akira Miyazaki,

    Corresponding author
    1. Department of Environmental Applied Chemistry, University of Toyama, Toyama 930-8555, Japan
    • Akira Miyazaki, Department of Environmental Applied Chemistry, University of Toyama, Toyama 930-8555, Japan

      Jean-René Hamon, Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France

      Claude Lapinte, Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France

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  • Frédéric Justaud,

    1. Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
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  • Frédéric Gendron,

    1. Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
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  • Jean-François Halet,

    1. Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
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  • Jean-René Hamon,

    Corresponding author
    1. Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
    • Akira Miyazaki, Department of Environmental Applied Chemistry, University of Toyama, Toyama 930-8555, Japan

      Jean-René Hamon, Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France

      Claude Lapinte, Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France

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  • Claude Lapinte

    Corresponding author
    1. Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
    • Akira Miyazaki, Department of Environmental Applied Chemistry, University of Toyama, Toyama 930-8555, Japan

      Jean-René Hamon, Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France

      Claude Lapinte, Institut des Sciences Chimiques de Rennes, UMR 6226, CNRS – Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France

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Abstract

The organic precursor bis(trimethylsilylethynyl)TTFMe2 (3, TTF = tetrathiafulvalene) was prepared as a 1:1 mixture of the cis and trans isomers. Pure samples of 3-cis and 3-trans were obtained by crystallization and identified by XRD analysis. The treatment of pure 3-trans and a 1:1 mixture of 3-cis/trans with (i) potassium carbonate, (ii) the iron complex Cp*(dppe)FeCl [5, Cp* = η5-C5Me5, dppe = 1,2-bis(diphenylphosphanyl)ethane] in the presence of KPF6, and (iii) tBuOK provided Cp*(dppe)Fe–C≡C–TTFMe2–C≡C–Fe(dppe)Cp* as the pure geometric isomer 6-trans (85 %) and as the 60:40 mixture 6-cis/trans (63 %), respectively. The oxidation of 6-trans with [(C5H5)2Fe]PF6 gave [6-trans][PF6]n (n = 1–3). Visible, IR, near-IR (NIR), and electron paramagnetic resonance (EPR) spectroscopy together with DFT data show that [6-trans][PF6] is a class II mixed-valence complex (Hab = 85 cm–1) in which the spin distribution depends on the conformation of the molecule. Intramolecular electron transfer occurs through single-step tunneling and a multistep hoping mechanism. The triplet state is thermally accessible for [6-trans][PF6]2.

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