Role of cation symmetry in intermolecular structure and dynamics of room temperature ionic liquids: simulation studies.

Molecular dynamics simulations of a series of bis(trifluoromethylsulfonyl)amide anion-based room temperature ionic liquids have been carried out to identify the effects of the molecular symmetry of the cation on the structure and dynamics of the liquid. Simulations of ionic liquids with imidazolium cation containing varying lengths of alkyl groups were performed. The calculated density and total X-ray scattering function of the liquids agree well with experimental data. Liquids containing symmetric cations ([C(n)C(n)im][NTf(2)]) are found to be more structured than those with asymmetric ones ([C(n)C(1)im][NTf(2)]), manifested in greater intermolecular ordering and slower dynamics.