-crystal , and the corresponding angles for the trans conformer were reported to be 69.9˚ and 75.8˚ in the [Cs] + [FSI] -crystal . The ωB97X-D functional approach which includes dispersion interactions is generally regarded as the most excellent alternative to deal with ionic liquids containing imidazolium based systems where the effect of dispersion interactions leads to ring stacking interactions and delicate intermolecular interactions like H-bonding . The interplay of both electrostatic and dispersion forces present in ionic liquids have been thoroughly studied from a range of computational viewpoints . Delicate intermolecular forces such as H-bonds and π-type interactions that simultaneously occur in ionic liquids are critical, and are key driving forces for local structuring in the liquid phase. Despite the absence of conclusive and universally accepted definition of H-bond, H-bonding is still a key area of debate on the properties of ionic liquids. The strength of H-bond can be related to the donor-acceptor distance and angle as a first estimate . This, of course, also depends on the nature of atoms involved and the angle between them. H-bond interaction. However, on the basis of geometric criteria given in Table , there are no C-H---N 1 and C-H---F interactions observed for the [EMI][FSI] single ion pair conformers.