Correlation of the empirical polarity parameters of solvate ionic liquids (SILs) with molecular structure

Empirical polarity parameters for 10 solvate ionic liquids (SILs) have been determined using Catalan's probes. The solvation environment surrounding the probe molecules in the SILs is dependent on the mutual interactions between the cation, anion and chelating ligand, leading to characteristic values of the polarity parameters. The acidity of the SILs is comparable to the acidity of polar protic solvents, which is attributed to the ability of the Li cation to interact with the probe in a manner similar to H-bond donor. The choice of anion influenced the measured acidity of SILs by determining the extent of cation-probe interactions possible. The basicity showed a strong correlation with the nature of the anion but was also influenced by the extent of cation-anion interaction and choice of ligand. Temperature dependence of polarity parameters in SILs is relatively small, but shows some interesting trends. (C) 2019 Elsevier B.V. All rights reserved.