Energetic bicyclic azolium salts

Bicyclic azoles, 2-methyl-5(imidazol-1-yl)-2H-tetrazole (1), 2-methyl-5-(1,2,4-triazol-1-yl)-2H-tetrazole (4), 1-methyl-5-(imidazol-1-yl)1H-tetrazole (7), 1-methyl-5-(1,2,4-triazol-1-yl)-1H-tetrazole (10), 1-methyl-4-nitro-2-(imidazol-1-yl)-1H-imidazole (13), and 1-methyl-4-nitro-2-(1,2,4-triazol-1-yl)-1H-imidazole (16) were prepared. Their thermally stable azolium salts, 3, 6, 9, 12, 15, and 18-21, with densities ranging between 1.519-1.674 gcm(-3), were synthesized by quaternization with nitric or perchloric acid or with iodomethane followed by metathesis reactions with silver nitrate and silver perchlorate. The structures of 12b and 21b were confirmed by single-crystal X-ray analysis. The standard enthalpies of formation for some of the new salts were calculated by using the computationally feasible DFT-(B3LYP) and MP2 methods in conjunction with an empirical approach based on densities of salts. The calculated values range from Delta H-f degrees = 209.9 (21 a) to 412.3 (12b)kJ mol(-1) in which the experimental densities are > 1.515 gcm(-3).