The Gradient Energetic Modification Method to Optimize the Balance between Energy and Thermal Stability of Tetrazole-Fused Pyrazolopyrimidines

In this work, a gradient energetic modification method was developed to systematically modulate the energy–stability balance through sequential structural modifications. Starting from nitrogen-rich fused heterocycle precursor 3-(1 H -tetrazol-5-yl)pyrazolo[1,5- a ]pyrimidine-2,7-diamine ( 3 ), sequential salt formation, oxidation, and nitration reactions afforded the corresponding perchlorate salt 2,7-diamino-3-(1 H -tetrazol-5-yl)pyrazolo[1,5- a ]pyrimidin-1-ium perchlorate ( 4 ), nitro compound 2-nitro-3-(1 H -tetrazol-5-yl)pyrazolo[1,5- a ]pyrimidin-7-amine ( 5 ), and nitramine compound N -(7-amino-6-nitro-3-(1 H -tetrazol-5-yl)pyrazolo[1,5- a ]pyrimidin-2-yl)nitramide ( 6 ), with a stepwise increase in detonation velocity from 7968 m·s –1 to 8069 m·s –1 and finally to 8533 m·s –1 . Concurrently, a gradual decline in thermal decomposition temperature was observed from 190.3 to 185.2 °C and ultimately to 181.7 °C; this progressive trade-off culminated in compound 6, which achieves a substantially enhanced detonation performance that was accompanied by only a slight decrease in thermal decomposition temperature, which remained within an acceptable range. Thus, the gradient energetic modification method developed herein achieves an optimal balance between enhanced detonation performance and retained structural stability.