Synthesis and Properties of Alkoxy- and Alkenyl-Substituted Peralkylated Imidazolium Ionic Liquids

Authors

  • Cedric Maton,

    1. Department of Sustainable Chemistry and Technology, SynBioC Research Group, Ghent University, Coupure Links 653, 9000 Ghent (Belgium), Fax: (+32) (9) 264 59 57
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  • Dr. Neil R. Brooks,

    1. Department of Chemistry, KU Leuven—University of Leuven, Celestijnenlaan 200F, 3001 Heverlee (Belgium)
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  • Prof. Dr. Luc Van Meervelt,

    1. Department of Chemistry, KU Leuven—University of Leuven, Celestijnenlaan 200F, 3001 Heverlee (Belgium)
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  • Prof. Dr. Koen Binnemans,

    1. Department of Chemistry, KU Leuven—University of Leuven, Celestijnenlaan 200F, 3001 Heverlee (Belgium)
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  • Dr. Stijn Schaltin,

    1. Department of Metallurgy and Materials Engineering (MTM), KU Leuven—University of Leuven, Kasteelpark Arenberg 44, 3001 Heverlee (Belgium)
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  • Prof. Dr. Jan Fransaer,

    1. Department of Metallurgy and Materials Engineering (MTM), KU Leuven—University of Leuven, Kasteelpark Arenberg 44, 3001 Heverlee (Belgium)
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  • Prof. Dr. Christian V. Stevens

    Corresponding author
    1. Department of Sustainable Chemistry and Technology, SynBioC Research Group, Ghent University, Coupure Links 653, 9000 Ghent (Belgium), Fax: (+32) (9) 264 59 57
    • Department of Sustainable Chemistry and Technology, SynBioC Research Group, Ghent University, Coupure Links 653, 9000 Ghent (Belgium), Fax: (+32) (9) 264 59 57

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Abstract

Novel peralkylated imidazolium ionic liquids bearing alkoxy and/or alkenyl side chains have been synthesized and studied. Different synthetic routes towards the imidazoles and the ionic liquids comprising bromide, iodide, methanesulfonate, bis(trifluoromethylsulfonyl)imide ([NTf2]), and dicyanamide {[N(CN)2]} as the anion were evaluated, and this led to a library of analogues, for which the melting points, viscosities, and electrochemical windows were determined. Incorporation of alkenyl moieties hindered solidification, except for cations with high symmetry. The alkoxy-derivatized ionic liquids are often crystalline; however, room-temperature ionic liquids (RTILs) were obtained with the weakly coordinating anions [NTf2] and [N(CN)2]. For the viscosities of the peralkylated RTILs, an opposite trend was found, that is, the alkoxy derivatives are less viscous than their alkenyl-substituted analogues. Of the crystalline compounds, X-ray diffraction data were recorded and related to their molecular properties. Upon alkoxy substitution, the electrochemical cathodic limit potential was found to be more positive, whereas the complete electrochemical window of the alkenyl-substituted imidazolium salts was shifted to somewhat more positive potentials.

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