Constructing high-energy insensitive fused-ring energetic materials via a strategy of maximizing the heat of formation†

The introduction of energetic groups can significantly increase the density of energetic materials, usually accompanied with the deterioration of safety performance, which has limited the development of advanced insensitive energetic materials. In this study, a strategy of maximizing the heat of formation was executed to synthesize five novel tetrazolo[1,5-b]pyridazine-based fused-ring energetic materials incorporating nitroguanidine, five-membered heterocycles, double fused rings or hydrazineylidene moieties through brief synthesis steps. Notably, the heat of formation of compound 9 was up to 4.55 kJ g⁻¹, which mainly resulted in exceptional detonation performance (D_v = 9121 m s⁻¹, P = 30.1 GPa) and excellent insensitivity (IS > 60 J, FS > 360 N), making it a promising replacement for HMX. Hirshfeld surface analysis and electrostatic potential calculations elucidated the crucial role of hydrogen bonding and molecular planarity caused by hydrazineylidene groups in achieving a balance between energy and sensitivity. These findings provide insights of great value for the design of advanced high-energy insensitive energetic materials.