A theoretical investigation of the interactions between hydroxyl-functionalized ionic liquid and water/methanol/dimethyl sulfoxide

Density functional calculations have been used to investigate the interactions of 1-(2-hydroxyethyl)-3-methylimidazolium (C₂OHmim]⁺)-based ionic liquids (hydroxyl ILs) with water (H₂O), methanol (CH₃OH), and dimethyl sulfoxide (DMSO). It was found that the cosolvent molecules interact with the anion and cation of each ionic liquid through different atoms, i.e., H and O atoms, respectively. The interactions between the cosolvent molecules and 1-ethyl-3-methylimizolium (C₂mim]⁺)-based ionic liquids (nonhydroxyl ILs) were also studied for comparison. In the cosolvent–nonhydroxyl ILs] systems, a furcated H-bond was formed between the O atom of the cosolvent molecule and the C2-H and C6-H, while there were always H-bonds involving the OH group of the cation in the cosolvent–hydroxyl ILs] systems. Introducing an OH group on the ethyl side of the imidazolium ring may change the order of solubility of the molecular liquids.