Structure-property relationships in ionic liquids: a study of the anion dependence in vaporization enthalpies of imidazolium-based ionic liquids.

Vaporization enthalpies for a series of ionic liquids (ILs) with the common cation 1-ethyl-3-methylimidazolium [C(2)mim] and different counter anions are determined using a quartz crystal microbalance method. Dependences of vaporization enthalpies on physicochemical parameters specific for cation and anion interactions are revealed. A linear relation between enthalpies of vaporization and the intermolecular vibrational frequencies is observed and suggested for calculation of unknown ILs. A simple group-contribution method is developed for prediction of vaporization enthalpies of alkyl imidazolium-based ILs.