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Proton-Induced Tuning of Metal–Metal Communication in Rack-Type Dinuclear Ru Complexes Containing Benzimidazolyl Moieties

Authors

  • Katsuaki Kobayashi,

    1. Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan), Fax: (+81) 3-3817-1908
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  • Masamichi Ishikubo,

    1. Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan), Fax: (+81) 3-3817-1908
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  • Katsuhiko Kanaizuka,

    1. Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan), Fax: (+81) 3-3817-1908
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  • Keiko Kosuge,

    1. Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan), Fax: (+81) 3-3817-1908
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  • Shigeyuki Masaoka,

    1. Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581 (Japan)
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  • Prof. Ken Sakai,

    1. Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581 (Japan)
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  • Prof. Koichi Nozaki,

    1. Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama-shi, Toyama 930-8555 (Japan)
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  • Prof. Masa-aki Haga

    Corresponding author
    1. Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan), Fax: (+81) 3-3817-1908
    • Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan), Fax: (+81) 3-3817-1908
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Abstract

Ru complexes bearing a bis-tridentate benzimidazolyl ligand have been synthesized. The dinuclear ones act as a bibasic acid with pKa1=4.36 and pKa2=5.90. The protonated form of the dinuclear complex exhibited two one-electron oxidations at +0.91 and +1.02 V versus the ferrocenium/ferrocene (Fc/Fc+) couple (the potential difference (ΔE)=0.11 V), but the di-deprotonated form showed two waves at +0.50 and +0.58 V versus Fc/Fc+E=0.08 V). Since the potential difference between two waves reflects the strength of the metal–metal interaction, the deprotonation of the benzimidazole moieties in the complexes weakened the Ru–Ru communication. The degree of electronic coupling between two metal centers, estimated from the intervalence charge transfer (IVCT) band, was greater for the protonated form. DFT calculations for the protonated and deprotonated forms of the dinuclear complex suggest that the RuIIL(H2) π* interaction plays a key role in the Ru–Ru interaction.

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