Direct synthesis, selective anion exchange, and DFT characterization of novel energetic heteroanionic dicationic ionic liquids.

New energetic heteroanionic dicationic ionic liquids (HeDILs) were synthesized from the reaction of epichlorohydrine and 1-methylimidazole in one-pot operation. Upon setting the reaction conditions, these simple and readily available starting materials delivered a fairly high yield of the ionic liquid consisting of 1,1'-(2-hydroxy-1,3-propandiyl)bis[3-methyl-1H-imidazolium] dication paired with two different anions. The as-prepared HeDIL allows the selective metathesis of its chloride anion, leading to production of analogous energetic HeDILs. The synthesized HeDILs were characterized experimentally by NMR and FT-IR spectroscopies, TGA and DSC thermal analysis and titrimetric anion measurements. The effect of anionic heterogeneity on configuration and energy of the HeDILs was explored by DFT computations. These calculations delineate a half-cup shape for the dominant conformation of the dication with its interior site being preferred by ClO occupation. This insight accounts for the relative resistance of ClO toward anion metathesis reaction of the parent HeDIL. Thermal analysis of the parent HeDIL by using a model-free iso-conversional method revealed that its exothermic decomposition has a complex kinetics.