Heterocyclic Energetic Salts of 4,4′,5,5′-Tetranitro-2,2′-Biimidazole

A series of nitrogen-containing heterocyclic 4,4′,5,5′-tetranitro-2,2′-biimidazolate salts was synthesized with the cations as pyridinium (3), pyrazolium (4), 3-amino-pyrazolium (5), imidazolium (6), N-methylimidazolium (7), 1,2,4-triazolium (8), 3-amino-1,2,4-triazolium (9), 3,5-diamino-1,2,4-triazolium (10), 1,2,3-triazolium (11), 1,5-diamino-tetrazolium (12), and 2,2′-biimidazolium (13). These salts were characterized by nuclear magnetic resonance, infrared spectroscopy, and elemental analysis. Their properties were measured or calculated. Salts 4, 6, 7, 8, and 9 were confirmed by single-crystal X-ray diffraction. Salt 13 with a bicyclic cation has the highest heat of formation of 3.06 kJ/g. With the highest detonation performance (29.9 GPa, 8,638 m/s) and low sensitivity (30 J, > 360 N), salt 12 is a promising candidate as an insensitive explosive.