5,6,5-Melting Tricyclic Conjugated System: An Effective Strategy for Balancing Stability and Energy

The field of energetic materials should prioritize the development of energy-rich backbones that possess both high energy and low sensitivity, in addition to exhibiting exceptional density and performance characteristics. For this purpose, three new heat-resistant and low-sensitivity energetic compounds with [5,6,5] fused ring skeletons were developed in this study: 9H-tetrazolo[1,5-b][1,2,3]triazolo[4,5-d]pyrimidin-6-ol (3), 9H-tetrazolo[1,5-b][1,2,3]triazolo[4,5-d]pyrimidin-6-amine (4), and 8-azino-8H-imidazo[4,5-d]tetrazolo[1,5-b]pyridazine-6-amine (5). It was determined through single-crystal X-ray diffraction and theoretical analysis that these three compounds exhibited low sensitivity (IS > 20 J and FS > 240 N). Their molecules are planar with abundant intermolecular hydrogen bonds and strong π–π interactions between the molecular layers, all of which account for their low sensitivity. At the same time, 3 (D = 7734 m·s^–1, P = 22.4 GPa), 4 (D = 8075 m·s^–1, P = 23.5 GPa), and 5 (D = 7889 m·s^–1, P = 22.2 GPa) have higher detonation performance than the conventional explosives HNS (D = 7612 m·s^–1, P = 24.3 GPa) and TNT (D = 6881 m·s^–1, P = 19.5 GPa). 4 has a maximum thermal decomposition temperature (T = 318 °C) comparable to that of the heat-resistant explosive HNS (T = 318 °C). The research findings suggest that compound 4 exhibits potential as a heat-resistant and low-sensitivity explosive, while compounds 3 and 5 demonstrate the potential to be low-sensitivity explosives.