An experimental and computational study to explore the ion–solvent interactions between selected ionic liquids and dimethylformamide

Solute-solvent, solute-solute and solvent-solvent interactions are examined <i>via</i> thermodynamics using apparent molar properties which are temperature dependent and are useful to define the isolated contribution of each component to the non-ideality of the mixture. Apparent molar volumes (<i>V</i> _ϕ) and apparent molar adiabatic compressibilities (<i>K</i> _ϕ) were investigated for three binary mixtures with different anions: 1-butyl-3-methylimidazolium chloride [Bmim][Cl], 1-butyl-1-methylpyrrolidinium chloride [Bmpym][Cl] and 1-butyl-3-methylimidazolium thiocyanide [Bmim][SCN] with dimethylformamide (DMF) at different temperatures (293.15-343.15) K and at ambient pressure. Density (<i>ρ</i>) and speed of sound (<i>u</i>) of the pure components and their mixtures were recorded. The data was fitted to the Redlich-Mayer polynomial equation to calculate the derived thermodynamic parameters: limiting apparent molar volume (<i>V</i> ⁰ _ϕ), limiting apparent molar expansion (<i>E</i> ⁰ _ϕ), thermal expansion coefficients (<i>α</i> _p) and limiting apparent molar adiabatic compressibility (<i>K</i> ⁰ _ϕ) along with their associated parameters (<i>S</i> _v, <i>B</i> _v, <i>S</i> _k, <i>B</i> _k). The primary focus of this study was to examine the effect of temperature on the anion and cation interaction of the IL with DMF and how these changes affected the IL structure. The computational investigation further examined the IL-solvent interaction energy and described the type of interaction in all three systems.