High Density of a New Fused Heterocycle: 7,8‐Dinitro‐4‐oxo‐4,6‐dihydropyrazolo[5, 1‐d][1, 2,3,5]tetrazine 2‐oxide and Its Energetic Salts

In this work, the new fused heterocyclic compound 7,8‐dinitro‐4‐oxo‐4,6‐dihydropyrazolo[5, 1‐d][1, 2,3,5]tetrazine (HPCM) and its energetic salts were designed and synthesized. All energetic salts were fully characterized by 1H and 13C nuclear magnetic resonance spectroscopy, infrared spectroscopy, and elemental analysis. The structures of the sodium and 3,4,5‐triamino‐1,2,4,–triazolium salts were further confirmed by single‐crystal X‐ray diffraction. In addition, their key physicochemical properties such as density, thermal stability, and sensitivity towards impact and friction were also evaluated. The salts were thermally stable with decomposition temperatures ranging from 171 to 315 °C. Theoretical calculations associated with heats of formation and detonation performance were performed by Gaussian 03 and EXPLO5 v6.01 programs, respectively. All of the salts were found to have positive heats of formation. Taking both experimental and computational parameters into consideration, the fact that hydroxylammonium salt showed a high density (ρ=1.95 g cm–3), acceptable decomposition temperature (Td=171 °C), excellent detonation performance (P=39.4 Gpa, vD=9228 m s–1) and favorable impact and friction sensitivities (IS=19 J, FS=360 N), indacate that it has the potential to be used as a less sensitive high energy density material. A facile and unique 7,8‐dinitro‐4‐oxo‐4,6‐dihydropyrazolo[5, 1‐d][1, 2,3,5]tetrazine 2‐oxide and its various of energetic salts have been prepared as high energy density materials. Representative hydroxylammonium salt featured a promising integrated energetic performance (vD=9228 m s−1, P=39.4 GPa, IS=19 J, and FS=360 N), which may prove to be a very competitive candidate for replacing of RDX.