Nitroguanidine-fused bicyclic guanidinium salts: a family of high-density energetic materials.

A series of nitroguanidine-fused bicyclic guanidinium energetic salts paired with inorganic energetic anions, mono- and di-tetrazolate anions were synthesized through simple metathesis reactions of 2-iminium-5-nitriminooctahydroimidazo[4,5-d]imidazole chloride and sulfate with the corresponding silver and barium salts, respectively, in aqueous solution. Key physical properties, such as melting point, thermal stability, and density were measured. The relationship between the structures of the salts and these properties was determined. The salts exhibit thermal stability and density (>1.60 g cm(-3)) that are comparable to currently used explosives The structures of the nitrate salt 1 and the dinitrocyanomethanide salt 4 were confirmed by single-crystal X-ray analysis. Densities, heats of formation, detonation pressures and velocities, and specific impulses were calculated. All of the salts possess positive calculated heats of formation and most of them exhibit promising energetic performance that is comparable with those of 1,3,5-trinitrobenzene (TNT), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), and cyclotrimethylenetrinitramine (RDX). The effect of the fused bicycle 2-iminium-5-nitriminooctahydroimidazo[4,5-d]imidazole on these physicochemical properties was examined and discussed.