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 π−π 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 °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.

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Fused heterocyclic energetic cation was rarely reported despite the development of energetic cation has attracted increasing attention in recent years. In this work, a new 1H-imidazo­[4,5-d]­pyridazine-2,4,7-triamine was synthesized in a one-step reaction, which was used as a cation to prepare 1H-imidazo­[4,5-d]­pyridazine-2,4,7-triamine perchlorate. Interestingly, when the synthesis was accomplished in different conditions, two crystal forms of perchlorate α-4 and β-4 were obtained, which were further confirmed by X-ray single crystal diffraction, X-ray powder diffractograms, infrared and multinuclear NMR spectra. These salts showed high density (1.88–1.93 g cm–3 at 293(2) K), moderate detonation performance (D, 8128–8437 m s–1; P, 29.4–32.86 GPa) and good thermal stability (T d: 272–274 °C). Compared with those known energetic perchlorates, the density and sensitivity (IS, 14–20 J; FS, 144–168 J) of 4 were also significantly improved. Through theoretical calculations and experiment results, the explanations for the differences in physicochemical properties of these two crystal forms were illustrated. Density overlap indicator (DORI) analysis was also employed to perform the necessary visualization and quantification of covalent and noncovalent interactions. It is evident that ionic bonds, hydrogen bonds, and π–π interactions are responsible for the high density and excellent performance of 1H-imidazo­[4,5-d]­pyridazine-2,4,7-triamine perchlorate, indicating that as-synthesized new material is a very promising cation in the construction of low-sensitivity high-energy compounds.