Formation of "quasi" contact or solvent-separated ion pairs in the local environment of probe molecules dissolved in ionic liquids.

The change from "quasi" contact to "quasi" solvent-separated ion-pair configuration in the local environment of a probe molecule in ionic liquids depends on the varying interaction strength of the chosen anions. The ion speciation in these Coulomb fluids could be shown by combining infrared spectroscopy, density functional theory calculations, and natural bond orbital analysis using a low-self-clustering probe molecule.