Structure-Performance Relationship in Thermally Stable Energetic Materials: Tunable Physical Properties of Benzopyridotetraazapentalene by Incorporating Amino Groups, Hydrogen Bonding, and π-π Interactions

Structure-performance investigation has become one of those significant trends for energetic materials and energetic crystallography inevitably. Herein, we report two new energetic materials deriving from a famous thermally stable explosive benzopyridotetraazapentalene, which was first developed by Huynh and Hiskey, et al., at Los Alamos National Laboratory. Owing to the incorporation of amino groups, these two energetic materials exhibit different amusing physical performance. Understanding their structures, properties, performances, and the relationship among them is the basis for the rational design of thermally stable energetic materials. Moreover, for these energetic conjugated systems, the density overlap regions indicator analysis was also employed for necessarily visualizing and quantifying the covalent and noncovalent interactions. It is evident that this strategy of incorporating amino groups into energetic materials increased the coplanarity of the energetic fused ring, owing to the contribution of hydrogen bonding and pi-pi interactions, which can further decrease their sensitivity. However, we also found that the integrity of intramolecular hydrogen-bonding interaction was the critical factor, which affected the thermal stability of energetic molecules with the amino groups inserting progressively. It is notable that diamino-substituted energetic compound 8 exhibits comparable thermal stability (320 degrees C) to that of HNS, more dense (d: 1.84 g cm(-3)), higher nitrogen content (37.43%), and lower sensitivity (impact sensitivity: 12 J, friction sensitivity > 360 N), superior to those of HNS. These discoveries can effectively assist the design and preparation of other promising thermally stable energetic materials toward future high-performing energy applications.