Synthesis and characterization of energetic salts based on a new coplanar bicyclic cation-5-amino-3-(5-amino-1,2,4-oxadiazol-3-yl)-1H-1,2,4-triazolium

Abstract

A novel coplanar bicyclic cation 3-(5-amino-1H-1,2,4-triazol-3-yl)-1,2,4-oxadiazol-5-amine (AOAT) was proposed to widen the research of energetic cations, and four salts were synthesized via neutralization reaction in high yield. The single-crystal X-ray diffraction, multinuclear NMR (1H and 13C), IR, MS spectra, elemental analysis, differential scanning calorimetry (DSC), and thermos-gravimetric (TG) analysis techniques were employed to verify and characterize the structures and thermal stability of the four salts respectively. Based on the combination of experimentally determined densities and enthalpies of formation, the energetic properties of the two energetic salts AOATP and AOATN were determined using EXPLO5 program. Compared with those known energetic salts, AOATP and AOATN exhibited high densities (1.829–1.871 g·cm−3), acceptable detonation performance (D: 8359–8465 m·s−1; P: 28.4–30.3 GPa), good thermal stability (Td: 177–238 °C), as well as satisfied mechanical sensitivities (IS: 16–22 J; FS: 188–216 N). Hirshfeld surfaces and assiciated 2D fingerprint plots as well as non-covalent interactions were adopted to examine the intermolecular interactions of the four salts. The results indicate that ionic bonds, hydrogen bonds, and π-π stacking interactions are responsible for the high densities and excellent properties of 5-amino-3-(5-amino-1,2,4-oxadiazol-3-yl)-1H-1,2,4-triazolium perchlorate and nitrate salts, suggesting that the AOAT is a potential cation in the construction of high-performance energetic materials and that cations with coplanar conjugated structures could effectively improve the detonation properties and stability.