Nitrogen-rich polycyclic pentazolate salts as promising energetic materials: theoretical investigating

Pentazolate (cyclo-N₅^-) salts are nitrogen-rich compounds with great development potential as energetic materials due to their full nitrogen anion. However, the densities of available N₅^- salts are generally low, which seriously lowers their performances. It is necessary to screen out cyclo-N₅^- salts with high density. To this end, eight new non-metallic cyclo-N₅^- salts based on fused heterocycle were designed. -NH₂, -NO₂, and -O^- groups were introduced into the compounds to adjust and improve the detonation performance and impact sensitivity of cyclo-N₅^- salts. By theoretical calculations and Hirshfeld surface analyses, the densities, heats of formation, detonation performance, sensitivities, and crystal structures of the title compounds were predicted, and the contribution of hydrogen bond as well as π-π stacking to the stability of cyclo-N₅^- salt was revealed. The results indicate that the densities of title compounds are higher than 1.85 g cm^‒3, and the sensitivities of these compounds are predicted to be lower than that of HMX. The detonation properties of a (D = 9.47 km s^-1, P = 41.21 GPa) and d (D = 9.44 km s^-1, P = 40.26 GPa) are better than those of HMX. These mean that using fused ring as a cation and introducing proper substituents are an effective method to improve cyclo-N₅^- salt's density and balance the detonation performance and sensitivity.