Azo Pyrazole Carboxylic Derivatives for Potential Energetic Materials

Abstract

Ideal energetic materials require high densities, favorable thermal stability, high-energetic characteristics, low sensitivity to impact and friction, and safe environmental compatibility. Moreover, in view of the need for large-scale production, the synthesis routes for energetic materials must be as short as possible. In this study, novel low-sensitivity energetic compounds 5,5′-(diazene-1,2-diyl)bis(3-(1H-tetrazol-5-yl)-1H-pyrazole-4-carbonitrile) (4), 1,2-bis(3-carboxy-4-nitro-1H-pyrazol-5-yl)diazene-1-oxide (5), and 5,5′-(diazene-1,2-diyl)bis(3-(1H-tetrazol-5-yl)-1H-pyrazole-4-carboxylic acid) (6) were simply and efficiently synthesized by cycloaddition and nitration reactions. For the sake of exploring their potential as energetic materials, elemental analysis, multinuclear NMR spectroscopy, infrared spectroscopy, and single-crystal X-ray diffraction were applied to investigate the properties of such compounds. The calculated detonation properties of 4−6 (7480−8190 m·s⁻¹) are superior to that of the traditional explosive TNT (6881 m·s⁻¹). In addition, 4−6 have higher decomposition temperatures (T_d = 212−260 °C) than RDX (T_d = 204 °C). Meanwhile, 5 and 6 also have lower mechanical sensitivities (IS = 40 J, FS > 360 N) than RDX (IS = 7.5 J, FS = 120 N). The results showed that the azo pyrazole carboxylic acid derivatives could be used as low-sensitivity energetic materials.