On the Role of the Dipole and Quadrupole Moments of Aromatic Compounds in the Solvation by Ionic Liquids

The diverse dipole and quadrupole moments of benzene and its 12 fluorinated derivatives are correlated to their solubility in the ionic liquid 1-ethyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide. Albeit empirical, the correlation was built taken into account molecular insights gained from ab initio calculations of the isolated aromatic Solute molecules and molecular dynamics simulations of all 13 aromatic solute plus ionic liquid solvent binary mixtures. This type of molecular-assisted approach unveiled a simple correlation between the dipole and quadrupole moments of the solutes and the ionic liquid solvent. It also revealed the complex nature of the interactions between aromatic compounds and ionic liquids, with the charge density functions of the former acting as a sort of molecular template that promotes the segregation of the ions of the latter and defines the fluid phase behavior (liquid-liquid demixing) of the corresponding binary mixtures. Such an approach can be extended to other systems involving the interactions of different types of solutes with ionic liquid solvents.