Dense and Durable Energetics: Pyrazine-Coupled Oxadiazole Frameworks

A series of symmetric C-C bonded pyrazine-bridged 1,3,4-oxadiazole-based energetic compounds (5-8) were designed, synthesized, and fully characterized using NMR, IR, EA, and DSC techniques. Compound 5 was further confirmed by single-crystal X-ray diffraction, while 7 was analyzed by ¹⁵N NMR spectroscopy. All the newly prepared energetic molecules exhibit high density, excellent thermal stability, favorable detonation performance, and low mechanical sensitivity to external stimuli such as impact and friction. Among them, neutral compound 5 shows particularly promising properties, with a high density of 1.87 g cm^-3, outstanding thermal stability (225 °C), low sensitivity to impact (12 J) and friction (360 N), and a good detonation velocity of 8161 m s^-1. Notably, compound 5 demonstrates superior thermal stability and mechanical insensitivity compared to previously reported symmetrical C-C bonded and azo-bridged nitramino azoles. Furthermore, the salts of compound 5 (6-7) and the potassium metal-organic network 8 also exhibit high density (1.74-2.01 g cm^-3), excellent thermal stability (200-292 °C), good detonation velocity (7327-8325 m s^-1), and remarkable insensitivity to mechanical stimuli (IS = 40 J; FS = 360 N). The novelty, synthetic accessibility, and energetic performance of these compounds suggest their strong potential as secondary explosives and thermally robust energetic materials for defense and civilian applications.