Constructing Planar C–N Bond-Linked Bi-Triazole High-Energy Explosives via the Formation of Salts

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. Synthesizing nitrate and perchlorate salts based on 3,4′,5-triamine-1,3′-bi(1,2,4-triazole) (1) is an effective way to improve the planarity of 1, thus reaching an optimum balance between a high level of detonation performance and low-sensitivity.