Competition between cation–solvent and cation–anion interactions in imidazolium ionic liquids with polar aprotic solvents
Résumé
The subtle interplay between ion solvation and association was analyzed in mixtures of imidazolium-based ionic liquids (ILs) with polar aprotic solvents. A site-specific pattern of cation–solvent and cation–anion interactions was disclosed by a careful analysis of the 1H and 13C NMR chemical shift dependence of the mixture composition. It was established that the less polar but more donating γ-butyrolactone is more prone to establish H-bonds with the imidazolium-ring hydrogen atoms of the IL cations than propylene carbonate, particularly at the H2 site and at high dilutions xIL<0.1. The H2 site was found to be more sensitive to intermolecular interactions compared to H4, 5 in the case of ILs with asymmetric anions like trifluoromethanesulfonate (TfO−) or bis(trifluoromethylsulfonyl)amide (TFSA−).