Novel 4,5-Dinitro-N,N′-dialkylimidazolium Cations as Candidates for High-energy Materials

In the synthesis of energetic ionic liquids (EILs), the quaternization of dinitroimidazoles remains a challenging task due to their reduced nucleophilicity. In this study, two new EILs precursors, 3-ethyl-1-methyl-4,5-dinitro-1H-imidazol-3-ium tetrafluoroborate (1) and 1,3-diethyl-4,5-dinitro-1H-imidazol-3-ium tetrafluoroborate (2) were obtained via the alkylation of 1-methyl-4,5-dinitro-1H-imidazole and 4,5-dinitro-1H-imidazole using Meerwein's reagents, respectively. The 4,5-dinitroimidazolium cations are expected to be applied for new insensitive high-energy materials (HEMs) via an anion metathesis reaction with energetic anions. Two new EILs, 3-ethyl-1-methyl-4,5-dinitro-1H-imidazol-3-ium 2,4,5-trinitroimidazol-1-ide (3) and 1,3-diethyl-4,5-dinitro-1H-imidazol-3-ium 2,4,5-trinitroimidazol-1-ide (4), were obtained as potential HEMs via the anion metathesis reaction with 2,4,5-trinitroimidazol-1-ide. Although some improvements in the thermal properties are desired, compound 3 showed the promising properties as a new insensitive HEM because of its excellent insensitivity and more powerful explosive performance than those of 2,4,6-trinitrotoluene (TNT).