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 ClO₄^- occupation. This insight accounts for the relative resistance of ClO₄^- 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.