Highly Thermostable Insensitive Energetic Polynitrophenyl-Substituted Furazan (Furoxan)-Annelated Azepines

Achieving high thermal stability and low mechanical sensitivity are two major goals in the development of energetic compounds. Six highly stable insensitive polynitrophenyl-substituted furazan (furoxan)-annelated azepines have been prepared and characterized in this work. All the involved compounds were characterized by 1H and 13C NMR spectroscopy, IR spectroscopy, and elemental analysis, and four of them were further supported by single-crystal X-ray diffraction investigations. Moreover, their thermal stabilities and mechanical sensitivities were evaluated. All energetic compounds exhibited excellent thermal stabilities with decomposition temperatures ranging from 290 to 333 °C. Compounds 1c and 2c exhibit extremely low mechanical sensitivity (IS >40 J and FS > 360 N). Based on experimental densities and calculated heat of formation, the detonation velocities and pressures for the energetic compounds were calculated using EXPLO5 (V6.04) with the corresponding results in the range of 26.4 to 29.9 GPa and 7979 m s-1 to 8356 m s-1. The detailed study based on Hirshfeld surfaces and electrostatic potential (ESP) analysis was used to illustrate the relationship between molecular structures and sensitivity of these compounds. The comprehensive performances of these materials are superior to those of the widely used heat-resistant explosive HNS (2,2′,4,4′,6,6′-hexanitrostilbene).