Experimental thermophysical properties and DFT calculations of imidazolium ionic liquids and 2-butanol mixtures

Abstract

Thermophysical properties, densities (ρ), speeds of sound (u) and dynamic viscosities (η) of binary mixtures constituting 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][CF3SO3])/1-ethyl-3-methylimidazolium ethyl sulfate ([EMIM][EtSO4]) (ILs) and 2-butanol have been measured experimentally. The obtained experimental data are further utilized to determine the excess molar volumes (VE), excess molar isentropic compressibilities (ΚsmE) and viscosity deviations (Δη) to gain insight into the molecular interactions of IL-2-butanol mixtures. In order to understanding the model fitting, the derived/excess properties are fitted to the Redlich-Kister polynomial equation. To unravel the effect of anions [CF3SO3]- and [EtSO4]- on molecular interactions, the Density Functional Theory (DFT) has been performed which provides the in-depth information about interactions in isolated ILs and their mixtures using DFT/D3-B3LYP method. Furthermore, the natural bond orbital (NBO) analysis has been performed to probe all possible interactions between donor-acceptor NBOs. This project aims to provide the experimental data of studied thermophysical properties and to obtain the interactional information at the molecular level between ILs having common cation and different anions and the solvent molecules in binary mixtures, which are interpreted in terms of ion-ion, ion-dipole and dipole-dipole interactions.