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Issue 14, 2014
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Extended scale for the hydrogen-bond basicity of ionic liquids

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In the past decade, ionic liquids (ILs) have been the focus of intensive research regarding their use as potential and alternative solvents in many chemical applications. Targeting their effectiveness, recent investigations have attempted to establish polarity scales capable of ranking ILs according to their chemical behaviours. However, some major drawbacks have been found since polarity scales only report relative ranks because they depend on the set of probe dyes used, and they are sensitive to measurement conditions, such as purity levels of the ILs and procedures employed. Due to all these difficulties it is of crucial importance to find alternative and/or predictive methods and to evaluate them as a priori approaches capable of providing the chemical properties of ILs. Furthermore, the large number of ILs available makes their experimental characterization, usually achieved by a trial and error methodology, burdensome. In this context, we firstly evaluated COSMO-RS, COnductor-like Screening MOdel for Real Solvents, as an alternative tool to estimate the hydrogen-bond basicity of ILs. After demonstrating a straight-line correlation between the experimental hydrogen-bond basicity values and the COSMO-RS hydrogen-bonding energies in equimolar cation–anion pairs, an extended scale for the hydrogen-bond accepting ability of IL anions is proposed here. This new ranking of the ILs' chemical properties opens the possibility to pre-screen appropriate ILs (even those not yet synthesized) for a given task or application.

Graphical abstract: Extended scale for the hydrogen-bond basicity of ionic liquids

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Publication details

The article was received on 15 Dec 2013, accepted on 10 Feb 2014 and first published on 10 Feb 2014

Article type: Paper
DOI: 10.1039/C3CP55285C
Citation: Phys. Chem. Chem. Phys., 2014,16, 6593-6601
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    Extended scale for the hydrogen-bond basicity of ionic liquids

    A. F. M. Cláudio, L. Swift, J. P. Hallett, T. Welton, J. A. P. Coutinho and M. G. Freire, Phys. Chem. Chem. Phys., 2014, 16, 6593
    DOI: 10.1039/C3CP55285C

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