Fused Pyrazolo[3,4-d] pyrimidine Nitrogen-rich Salts with Balanced Energetic Performance

Abstract

In this study, a series of novel energetic salts were synthesized and characterized using a pyrazolo[3,4-d]pyrimidine-derived fused tetracyclic backbone. All of them exhibit good densities, good detonation parameters, and low sensitivity toward mechanical stimuli. Detonation testing revealed that the detonation performance of compound 4c produces a dent of 36 × 31 mm on a lead plate, qualifying it as a potential secondary explosive.High-energy-density materials (HEDMs) are known to store large amounts of chemical energy per unit mass and deliver very high performance upon initiation, which has diverse applications, including weaponry, rocket propulsion, and engineering explosives. [1][2][3][4] As carriers of high-density chemical energy, these materials are vital to both national defense technologies and broader industrial and economic development. In the pursuit of high-performance energetic compounds, nitrogen-rich heterocyclic structures have attracted significant attention. 5,6 Current research emphasizes the development of new heterocyclic frameworks that exhibit a positive heat of formation (HOFs), high density, favourable oxygen balance, and reduced sensitivity to external stimuli such as impact, friction, and electrostatic discharge. 5,7 Among all heterocyclic ring backbones, 1,2,4-triazole, pyrazole, and pyrimidine have been widely studied due to their good stability, high energy content, and importantly, the ability to incorporate multiple functional groups on them. 8-10 Their energetic performance and oxygen balance can be further optimized by introducing various explosophoric groups such as nitramine (-NHNO2), trinitromethyl (-C(NO2)3), azide (-N3), and nitroimine (=N-NO2). 11,12 Polynitro-substituted compounds represent an essential class of high-performing energetic materials. [13][14][15] In particular, the trinitromethyl and nitramino groups significantly enhance the oxygen balance, nitrogen content, density, and explosive performance of energetic compounds. As highly