Influence of temperature and concentration on the molecular interactions of pyrrolidinium-based ionic liquid with water and alcohols: An experimental and DFT studies

The purpose of the present work is to explore the influence of concentration and temperature on solute–solvent interactions of binary mixtures of ionic liquid (IL) 1-methyl-1-propyl pyrrolidinium tetrafluoroborate ([MPpyr][BF4]) and water, alcohols (methanol and ethanol) at 298.15, 303.15, 308.15 and 313.15 K under atmospheric pressure. The thermophysical properties such as the apparent molar volume (Vϕ), apparent molar adiabatic compressibility (κϕ), and limiting apparent molar volumes (Vϕ0), limiting apparent molar adiabatic compressibility (κϕ0), the limiting apparent molar expansibility (Eϕ0), thermal expansion coefficients (αP) were evaluated from experimental density (ρ) and speed of sound (u) data using suitable Redlich–Mayer type equation. Vϕ0 and (κϕ0) values explain that the IL-solvent interaction in water, are stronger than the those between either methanol or ethanol with IL. Density functional theory (DFT) results are performed using the B3LYP/6–31++G (d,p) method, shows that the prominent interactions within the IL which are aliphatic C–H···anion interactions while the prominent interactions between the IL and the selected solvents are O − H···anion solute–solvent interactions. More importantly, DFT results confirm the trends observed from experimental findings, that the interaction involving IL in water is stronger than those involving either methanol or ethanol solvent with IL.