Solvation in molecular ionic liquids

Solvation in 1-ethyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium hexafluorophosphate is studied via molecular dynamics simulations by employing a diatomic solute as a probe. It is found that solvent fluctuations are chacterized by at least two distinct dynamics occurring on vastly different time scales—rapid subpicosecond dynamics arising mainly from anion translations and slow relaxation ascribed to anion and cation diffusions. Fast subpicosecond dynamics are responsible for more than 50% of the entire relaxation of solvent fluctuations in the temperature range $\text{350\hspace{0.17em}}\mathrm{K}\text{⩽T⩽500\hspace{0.17em}}\mathrm{K}.$ It is also found that solvent spectral shifts and reorganization free energies in these liquids are comparable to those in ambient water.