Prediction of the melting points for two kinds of room temperature ionic liquids

Melting points are significant properties for the design and application of ionic liquids (ILs) as green solvents. In this work, the melting points of two kinds of room temperature ionic liquids, imidazolium tetrafluoroborates and imidazolium hexafluorophosphates, were investigated by using a quantitative structure–property relationship (QSPR) approach. The employed descriptors were firstly selected by studying the optimized geometries of four ILs: EmimBF4, BmimBF4, EmimPF6 and BmimPF6. Electrostatic, quantum mechanical and topological descriptors were considered efficient to describe melting points of ionic liquids. A three-parameter model with the squared correlation coefficient, R2, of 0.9047 is developed for 16 kinds of imidazolium tetrafluoroborates, and a six-parameter equation with R2 of 0.9207 is obtained for 25 kinds of imidazolium hexafluorophosphates. The proposed models can be useful for the prediction of the melting points of ILs with similar structural features.