Synthesis, characterization and properties of new heat resistant energetic materials based on two C–C bridged pyrazole and benzene skeletons

Abstract

Two kinds of heat-resistant explosives, 3,5-bis-(2,4-dinitrophenyl)-4-nitro-1H-pyrazole (1c) and 1,4-bis-(3,5-dinitropyrazolyl)-2,5-dinitrobenzene (2c), were synthesized and thoroughly characterized by elemental analysis, infrared spectroscopy, ¹H and ¹³C NMR and high resolution mass spectrometry. The structures of 1c and 2c were confirmed by single-crystal X-ray diffraction and analyzed using different computing software (Multiwfn, Gaussian 09W, Diamond 3.0 and CrystalExplorer). In addition, we also investigated the thermal stabilities of these compounds by differential scanning calorimetry (DSC). 1c (T_d = 352 °C) and 2c (T_d = 321 °C) showed excellent thermal stabilities. The detonation properties were calculated using the EXPLO5 v6.05.04 program. The results revealed that 2c (D = 8304 m s⁻¹, P = 30.1 GPa) showed a higher detonation velocity and pressure than the widely used heat-resistant explosive 2,2′,4,4′,6,6′-hexanitrostilbene (HNS: D = 7612 m s⁻¹, P = 24.3 GPa). Furthermore, impact sensitivity and friction sensitivity tests revealed that 1c and 2c (IS > 40 J, FS > 360 N) were insensitive. Combining the above results, these compounds have the potential to become heat-resistant energetic materials.