One-step synthesis of low-melting pyrazole-based zwitterionic energetic materials with high energy density and prominent laser ignition behavior

Abstract

To explore low-melting zwitterionic energetic materials with high energy density, this study used 4,5-diamino-1-(2-hydroxyethyl)pyrazole sulfate as the starting material and controllably synthesized two pyrazole-based zwitterionic energetic materials (2 and 3) via a one-step straightforward approach. Single-crystal X-ray diffraction verified that compound 3 possesses a crystal density of 1.842 g cm⁻³ and exhibits a zero-oxygen balance. Thermal analysis showed that the melting points of 2 and 3 are 99 °C and 118 °C, with decomposition temperatures of 181 °C and 196 °C, respectively. Calculations using EXPLO5 V6.05 gave detonation velocities of 8081 m s⁻¹ (2) and 8901 m s⁻¹ (3), and detonation pressures of 26.54 GPa (2) and 35.03 GPa (3). BAM tests indicated impact sensitivities (IS) of 6 J (2) and 4 J (3), and friction sensitivities (FS) of 160 N (2) and 240 N (3). NASA CEA calculations suggest that compounds 2 and 3 possess promising gas-generation and energy-release potential for energetic formulation design. The as-synthesized zwitterions exhibit excellent laser responsiveness and can act as promoters for igniting AP or DATNBI. This work provides new insights into the design of low-melting zwitterionic energetic materials and laser-ignition promoters.