Synthesis, characterization and properties of amphoteric heat-resistant explosive materials: Fused [1,2,5]oxadiazolo [3′,4′:5,6]pyrido[4,3-d][1,2,3]triazines

Abstract

• The tricyclic triazine oxide was synthesized as the first fused amphoteric energetic molecule. • These compounds exhibited high decomposition temperatures (310–344 °C). • All the non-metallic compounds have better detonation properties than HNS and PYX and low sensitivities. • The perchlorate salt is a potential candidate for heat-resistant explosive. Fused cyclic energetic compounds are a unique class of large conjugated structures containing two or more rings, and have been identified as promising competitors for traditional energetic materials. In the present work, we investigated 5-amino-6-oxo-4,6-dihydro-[1,2,5]oxadiazolo[3′,4′:5,6]pyrido[4,3- d ][1,2,3]triazine 8-oxide ( 3 ) in detail as a fused amphoteric energetic molecule that can be protonated and deprotonated by acids and bases to obtain its cationic ( 11 – 13 ) and anionic ( 4 – 10 ) salts. All the new compounds were thoroughly characterized by infrared and multinuclear NMR ( 1 H and 13 C) spectroscopy, and elemental analysis. The structural features of 3 – 6 , 9 , 10 , 12 , and 13 were investigated by single-crystal X-ray diffractions and different theoretical techniques (Hirshfeld surfaces analyses, and noncovalent interactions). The aromaticity of compound 3 was studied via localized orbital locator- π and iso -chemical shielding surfaces (ICSS). Their thermal decomposition temperatures were investigated by differential scanning calorimetry and thermogravimetry to be 310–344 °C (onset). In addition, impact and friction tests revealed that these compounds were insensitive. Densities, heats of formation and detonation properties were measured by a gas pycnometer, calculated using the Born-Haber energy cycle and EXPLO5 v6.05.04 program, respectively. The neutral compound 3 and all its non-metallic salts have better detonation properties than HNS and PYX and lower sensitivities. In particular, salt 11 (N + O: 61.74 %, T d : 330 °C, Δ H f : 1.68 kJ g −1 , D : 8.795 km s −1 , P : 36.0 GPa, IS: > 40 J, FS: > 360 N) is a potential candidate for heat-resistant explosives.