A simulation study of CS₂ solutions in two related ionic liquids with dications and monocations

Atomistic simulations of solutions of CS₂ in an ionic liquid, $$ , with a divalent cation and in the corresponding ionic liquid with a monovalent cation, [C₄C₁im][NTf₂], were carried out. The low-frequency librational density of states of the CS₂ was of particular interest in view of recent optical heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES). Compared to the monocation ionic liquid, the maximum shifts to higher frequencies in the dication ionic liquid under ambient conditions, but was found to be significantly pressure-dependent. CS₂ molecules lie above and below the plane of the imidazolium rings and found to be close to the butyl tails of the monocation. The diffusion rates and embedding energies of solvent ions and CS₂ in the two ionic liquids were measured.