Theoretical study on the interactions between methanol and imidazolium-based ionic liquids.

To better understand the property of the binary systems composing of imidazolium salt, [emim](+)A- (A=Cl-, Br-, BF(4)-, and PF(6)-) and methanol, we have investigated in detail the interactions of methanol molecule with anions A-, cation [emim](+), and ion pair [emim](+)A- of several ionic liquids (ILs) based on 1-ethyl-3-methylimidazolium cation by performing density functional theory calculations. It is found that H-bonds are universally involved in these systems, which may play an important role for the miscibility of methanol with imidazolium-based ILs. The interaction mechanisms of methanol molecule with anion and cation are found to be different in nature: the former mainly involves LP(X)-[Formula: see text] interaction, while the latter relates with the decisive orbital overlap of the type of LP(O)-[Formula: see text]. Based on the present calculations, we have provided some reasonable interpretations for properties of the binary mixtures of ILs and alcohol and revealed valuable information for the interaction details between ILs and alcohols, which is expected to be useful for the design of more efficient ILs to form superior solvent system with alcohol.