Thermodynamic and structural properties of the ionic liquid binary system of 1-ethyl-3-methylimidazolium thiocyanate and methanol

Abstract

A binary mixture of ionic liquid 1-ethyl-3-methylimidazolium thiocyanate ([C2mim][SCN]) and methanol was prepared along with the whole composition range. Thermodynamic properties such as densities, dynamic viscosities, and electrical conductivities of binary system were measured from 293.15 to 323.15 K at 101.3 KPa. The electrical conductivities dependences of IL mole fraction were graphically described by the Casteel–Amis four-parameter equation. The excess molar volumes (VE ) and dynamic viscosity deviations (Δη) of the binary mixture were calculated and satisfactorily fitted by the Redlich–Kister polynomial equation to reveal the interactions that exist among the components. For a deep understanding of the intermolecular interactions of the binary mixture, the infrared spectrum analysis was used to provide the observable changes related to the structural features, and the stable structures, energies of the complexes involving cation or anion of [C2mim][SCN] and methanol molecule were calculated by density functional theory calculations at B3LYP/6-311++G** level of calculation to evaluate the interaction situations of the IL and methanol.