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).