Synthesis of novel insensitive heat-resistant explosives based on a fused-tricyclic skeleton†

Development of energetic materials with enhanced thermostability and diminished sensitivity is one of the main objectives of current research. In this work, an N,N-alkylidene bridge was used to synthesize a series of tricyclic heat-resistant fused ring compounds. The physical and chemical properties of newly synthesized compounds are verified and quantified through experimental and theoretical methods. The structures of all fused compounds were determined through single-crystal X-ray diffraction, elemental analysis, NMR spectroscopy, and IR spectroscopy. Among these compounds, 9-nitro-5,6-dihydrotetrazolo[1,5-a][1,2,4]triazolo[5,1-c]pyrazine (3) and 10-nitro-6,7-dihydro-5H-tetrazolo[1,5-a][1,2,4]triazolo[5,1-c][1,4]diazepine (4) exhibit excellent thermal stability with the decomposition temperatures higher than 300 °C (3: 301 °C and 4: 311 °C). Furthermore, compounds 3 and 4 are more insensitive in comparison with the applied heat-resistant material HNS (3: IS = 33 J, FS > 360 N; 4: IS > 40 J, FS > 360 N; HNS: IS = 5 J, FS = 240 N). Additionally, compound 3 displays significantly superior detonation properties compared to HNS (3: V_D = 8021 m s⁻¹, P = 25.8 GPa; HNS: V_D = 7612 m s⁻¹, P = 24.3 GPa). The potential of compound 3 as a heat-resistant material is demonstrated by these experimental and theoretical data.