As a momentous energetic group, a nitro group widely exists in high-energy-density materials (HEDMs), such as trinitrotoluene (TNT), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), etc. The nitro group has a significant effect on improving the oxygen balance and detonation performances of energetic materials (EMs). Moreover, the nitro group is a strong electron-withdrawing group, and it can increase the acidity of the acidic hydrogen-containing nitrogen-rich energetic compounds to facilitate the construction of energetic ionic salts. Thus, it is possible to design nitro-nitrogen-rich energetic compounds with adjustable properties. In this paper, the nitration methods of azoles, including imidazole, pyrazole, triazole, tetrazole, and oxadiazole, as well as azines, including pyrazine, pyridazine, triazine, and tetrazine, have been concluded. Furthermore, the prospect of the future development of nitrogen-rich heterocyclic energetic compounds has been stated, so as to provide references for researchers who are engaged in the synthesis of EMs.

Energy and safety are the two most concerning properties of energetic materials (EMs). Design and synthesis of planar molecules is considered to be an effective way to obtain high-energy low-sensitivity EMs. In this study, a new C–N bond-linked energetic bi-triazole compound, 3,4′,5-triamine-1,3′-bi(1,2,4-triazole) (1), and its nitrate (1a) and perchlorate salt (1b), as well as a nitrification product, 5-amino-3,4′-dinitramide-1,3′-bi(1,2,4-triazole) (2), and corresponding sodium (2a) and potassium salt (2b) were designed and synthesized. All compounds were fully characterized. The molecular structures of 1, 1a, 1b, 2a, and 2b were confirmed by single-crystal X-ray structure analyses. It was found that 1 exhibits non-planar loose molecular stacking, while 1a, 1b, and 2b exhibit compact face-to-face layered molecular packing structures, and salt 2a exhibits compact wave-like stacking. The physicochemical properties of all compounds, such as density, thermal stability, and mechanical sensitivity, were studied. 1, 1a, 1b, 2a, and 2b have low impact and friction sensitivity and good thermal stability. In addition, Hirshfeld surfaces (HS), independent gradient model (IGM) analyses combined with single-crystal analyses revealed intermolecular interactions in 1, 1a, 1b, 2a, and 2b and clarified the relationship between the structures and molecular properties. The sophisticated hydrogen bonds between the bi-triazole molecules and nitrate/perchlorate ions are the driving force of formation of planar structures. Detonation properties calculated with the professional software package EXPLO5 showed that nitrate 1a (D = 8872 m·s−1, P = 34.8 GPa) and perchlorate 1b (D = 8956 m·s−1, P = 35.1 GPa) exhibit good detonation performance.