Equilibrium of contact and solvent-separated ion pairs in mixtures of protic ionic liquids and molecular solvents controlled by polarity.

Polarity controls the equilibrium constants and free energies of contact ion pairs (CIPs) and solvent-separated ion pairs (SIPs) in mixtures of protic ionic liquids and molecular solvents. The subtle balance between the ionic species was studied by far-infrared difference spectra and related DFT-calculated properties for solvents of low and high polarity and for different solvent concentrations.