Synthesis, structure and properties of neutral energetic materials based on N-functionalization of 3,6-dinitropyrazolo[4,3-c]pyrazole

Abstract

3,6-Dinitropyrazolo[4,3-c]pyrazole (DNPP, 4) was prepared using an efficient modification process. Various neutral energetic derivatives of DNPP were synthesized from N-functionalization of imide (NH) group. All compounds were fully characterized by ¹H and ¹³C nuclear magnetic resonance spectroscopy, infrared spectroscopy, elemental analysis, and differential scanning calorimetry (DSC). The crystal structures of compounds 4·2H₂O, 12 and 15 were confirmed by single-crystal X-ray diffraction, showing extensive hydrogen-bonding. The densities of neutral derivatives ranged from 1.74 to 1.95 g cm⁻³, and all compounds have positive heats of formation in the range of 18.8 to 863 kJ mol⁻¹. Based on the measured densities and calculated heats of formation, theoretical performance calculations, including detonation pressures (27.1–41.5 GPa) and velocities (7819–9364 m s⁻¹), were carried out using the Gaussian 09 program and Kamlet–Jacobs equations, and they compare favorably with those of TNT and RDX. These properties make them potential and competitive for use as new high energy-density materials.