Theoretical study on the interactions between methanol and imidazolium-based ionic liquids

To better understand the property of the binary systems composing of imidazolium salt, [emim]+Aˉ (A=Clˉ, Brˉ, BF4ˉ, and PF6ˉ) and methanol, we have investigated in detail the interactions of methanol molecule with anions Aˉ, cation [emim]+, and ion pair [emim]+Aˉ of several ionic liquids (ILs) based on 1-ethyl-3-methylimidazolium cation by performing density functional theory calculations. It is found that H-bonds are universally involved in these systems, which may play an important role for the miscibility of methanol with imidazolium-based ILs. The interaction mechanisms of methanol molecule with anion and cation are found to be different in nature: the former mainly involves LPX-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \sigma_{{O - H}}^{*} $$\end{document} interaction, while the latter relates with the decisive orbital overlap of the type of LPO-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \sigma_{{C - H}}^{*} $$\end{document}. Based on the present calculations, we have provided some reasonable interpretations for properties of the binary mixtures of ILs and alcohol and revealed valuable information for the interaction details between ILs and alcohols, which is expected to be useful for the design of more efficient ILs to form superior solvent system with alcohol.