Towards improved explosives with a high performance: N-(3,5-dinitro-1H-pyrazol-4-yl)-1H-tetrazol-5-amine and its salts

Abstract

To reach the long-term, strongly desired goal of high energy density materials (HEDM), a novel N-bridged structure of N-(3,5-dinitro-1H-pyrazol-4-yl)-1H-tetrazol-5-amine, and its selected nitrogen-rich energetic salts are designed and synthesized. All compounds are fully characterized by ¹H and ¹³C NMR (in some cases, ¹⁵N NMR) spectroscopy, IR spectroscopy, HRMS and elemental analysis. Of these, salts 6·H₂O and 10 are further confirmed by single-crystal X-ray diffraction. The densities of these compounds ranged from 1.67 to 1.86 g cm⁻³. All energetic salts exhibit excellent thermal stabilities with decomposition temperatures ranging from 216 to 299 °C and all are insensitive to impact. Decomposition of these thermally stable compounds (salts 2, 3, and 4) occurs at 299, 296, and 290 °C, respectively. Theoretical performance calculations (Gaussian 03 and EXPLO5 v6.01) provide detonation pressures and velocities for the energetic salts in the ranges 25.9–37.4 GPa and 8264–9364 m s⁻¹, respectively; six of the energetic compounds have detonation velocities >9000 m s⁻¹. Notably, the unique overall performance of salt 4 thus exceeds those of commonly used explosives such as HMX. Thus, due to its insensitivity (IS > 40 J, FS = 360 N), fairly high detonation velocity (v_D = 9364 m s⁻¹), exceptional thermal stability (T_d = 290 °C), and high nitrogen content (N = 56.4%), salt 4 is a prospective candidate for a new class of insensitive, highly energetic explosives.