Heat-Resistant Energetic Materials Deriving from Benzopyridotetraazapentalene: Halogen Bonding Effects on the Outcome of Crystal Structure, Thermal Stability and Sensitivity

Heat-resistant energetic material (HREM) has shown its broad applications in petroleum and natural gas exploration, aerospace vehicle as well as solid rocket formulations. Benzopyridotetraazapentalene (BPTAP) (d: 1.84 g cm⁻³, D: 7670 m s⁻¹, IS: 9 J, T_d: 366 °C) is a heat-resistant energetic material, which is more dense and energetic than those of commercial HREM hexanitrosilbene (HNS) (d: 1.74 g cm⁻³, D: 7612 m s⁻¹, IS: 5 J, T_d: 318 °C). However, low solubility in most of commonly-used solvents has restricted its applications in detonators as nano-energetic materials. Meanwhile, recognition on this fused organic backbone is still limited. Herein, we report a chlorine-inclusion strategy and facile approaches to yield three new derivatives of BPTAP. It is notable that compound 6-a exhibits its high density (1.92 g cm⁻³), superior thermal stability (T_d: 334 °C), high detonation performance (D: 8084 m s⁻¹), comparable sensitivity (IS: 3 J) to that of HNS, surpassing those of commercially-used highly-sensitive primary energetic material lead azide (LA). It is interesting that the chlorine-inclusion in different position of fused benzopyridotetraazapentalene framework has greatly affected their physical properties such as crystal structure, thermal stability and sensitivity. This investigation offers a unique perspective for deeply exploring the relationship between structure and performance of energetic materials.