Pyrazolo[1,5-a]pyrimidine with similar “amino–nitro–amino” arrangement characteristics to TATB: a novel heat-resistant explosive with fused structure

Abstract

Exploring heat-resistant explosives that are easy to synthesize is a major challenge in the research of energetic materials. In this study, two novel fused-ring energetic compounds, namely 3,6-dinitropyrazolo[1,5-a]pyrimidine-5,7-diamine (4) and 5-amino-3,6-dinitropyrazolo[1,5-a]pyrimidin-7(4H)-one (5), were successfully prepared via a simple synthetic method. In addition, their structure, thermal stability, mechanical sensitivity and detonation performance were fully explored. Noteworthily, compounds 4 and 5 both exhibit excellent thermal stability (T_D(4) = 325 °C and T_D(5) = 291 °C), particularly compound 4, which features an “amino–nitro–amino” arrangement similar to that of TATB and exhibits a high density of 1.88 g cm⁻³ and a greater thermal decomposition temperature than hexanitrostilbene (HNS, 316 °C). In addition, due to the aza-fused structure, 4 and 5 possess higher positive heats of formation (332.9 kJ mol⁻¹ and 181.4 kJ mol⁻¹) than LLM-105 (11.0 kJ mol⁻¹). These advanced features endow 4 and 5 with superior detonation performance (V_d(4) = 8338 m s⁻¹ and P(4) = 30.7 GPa; V_d(5) = 8097 m s⁻¹ and P(5) = 29.8 GPa) than TATB (V_d = 8179 m s⁻¹ and P = 30.5 GPa) and HNS (V_d = 7170 m s⁻¹ and P = 21.8 GPa). This study enriches prospects for the molecular design and crystal engineering of novel energetic materials with admirable molecular stability.