Combination of Trinitromethyl Groups and Fused-Ring Skeletons for Construction of High-Energy and Low-Sensitivity Energetic Compounds

The difficulty in developing new trinitromethyl energetic materials stems from the need to balance the opposing properties of high energy and low sensitivity. This study reports new synthetic compounds based on the combination of trinitromethyl groups and a fused-ring system. In this work, three novel fused-ring compounds, 7-amino-3-nitro-2-(trinitromethyl)pyrazolo[1,5-a]pyrimidine-6-carboxylic acid (3), 3-nitro-6-(1H-tetrazol-5-yl)-2-(trinitromethyl)pyrazolo[1,5-a]pyrimidin-7-amine (5), and 3,6-dinitro-2-(trinitromethyl)pyrazolo[1,5-a]pyrimidin-7-amine (7), were all synthesized through cyclization and nitration reaction. Compounds 3 (V_D = 8549 m·s^–1, ρ = 1.79 g·cm^–3) and 5 (V_D = 8520 m·s^–1, ρ = 1.80 g·cm^–3) both demonstrate high density and detonation velocities that closely resembles that of RDX (V_D = 8795 m·s^–1, ρ = 1.80 g·cm^–3). Remarkably, compound 7 featured with an ortho amino-nitro group exhibits a higher density of 1.82 g·cm^–3 and more excellent detonation performance (V_D = 8867 m·s^–1, P = 35.1 GPa) than RDX (V_D = 8795 m·s^–1, P = 34.9 GPa). Compounds 5 and 7 both exhibit better thermal stability (T_d (5) = 155 °C and T_d (7) = 178 °C) compared with those of the already synthesized trinitromethyl energetic compounds. In addition, compounds 5 (IS = 16 J, FS = 168 N) and 7 (IS = 14 J, FS = 144 N) both exhibit sensitivity lower than that of RDX (IS = 7.4 J, FS = 120 N). The above results suggest the great application potentials of compound 7 as a high-energy and low-sensitivity energetic material.