Evidence of C--F-P and aromatic π--F-P weak interactions in imidazolium ionic liquids and its consequences

A simple change from alkyl group to alkene in side chain of imidazolium cation with same anion resulted in a drastic impact on physical properties (e.g., melting point) from bmimPF6 IL to cmimPF6 IL. The underlying reasons have been elucidated by structural and interactions studies with the help of DSC, SCXRD, vibrational and multi-nuclear NMR spectroscopic techniques. Experiments reveal existence of new weak interactions and helped to form different type of supramolecular arrangement, resulting in quite high melting point for cmimPF6 IL compared to bmimPF6 IL.219