Ionic Liquids of Cationic Sandwich Complexes

Authors

  • Takashi Inagaki,

    1. Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai, Nada, Hyogo 657-8501 (Japan), Fax: (+81) 78-803-5679
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  • Prof. Dr. Tomoyuki Mochida,

    Corresponding author
    1. Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai, Nada, Hyogo 657-8501 (Japan), Fax: (+81) 78-803-5679
    • Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai, Nada, Hyogo 657-8501 (Japan), Fax: (+81) 78-803-5679
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  • Prof. Dr. Masashi Takahashi,

    1. Department of Chemistry, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510 (Japan)
    2. Research Center for Materials with Integrated Properties, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510 (Japan)
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  • Dr. Chikahide Kanadani,

    1. Research Center for Materials with Integrated Properties, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510 (Japan)
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  • Prof. Dr. Toshiaki Saito,

    1. Research Center for Materials with Integrated Properties, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510 (Japan)
    2. Department of Physics, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510 (Japan)
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  • Prof. Dr. Daisuke Kuwahara

    1. The University of Electro-Communications, Chofugaoka, Chofu, Tokyo 182-8585 (Japan)
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Abstract

Simple cationic sandwich complexes that contained alkyl- or halogen substituents provided ionic liquids (ILs) with the bis(perfluoroalkanesulfonyl)imide anion. Ferrocenium- and cobaltocenium ILs [M(C5H4R1)(C5H4R2)][Tf2N] (M=Fe, Co) and arene–ferrocenium ILs [Fe(C5H4R1)(C6H5R2)][Tf2N] were prepared and their physical properties were investigated. A detailed comparison of their thermal properties revealed the effects of molecular symmetry and substituents on their melting points. Their viscosity increased on increasing the length of the substituent on the cation and the perfluoroalkyl chain length on the anion. Upon cooling, ILs with low viscosities exhibited crystallization, whereas those with higher viscosities tended to exhibit glass transitions. Most of these salts showed phase transitions in the solid state. A magnetic-switching phenomenon was observed for the paramagnetic ferrocenium IL, which was associated with a liquid/solid transformation, based on the magnetic anisotropy of the ferrocenium cation. 57Fe Mössbauer spectroscopy was applied to [Fe(C5H4nBu)2][Tf2N] to investigate the vibrational behavior of the iron atom in the crystal and glassy states of the ferrocenium IL.

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