Redefining 1,3,4-Oxadiazoles: Bridged Architectures for Balanced Energetic Performance

Methylene- and nitroso-bridged 1,3,4-oxadiazole-based energetic compounds have been synthesized through efficient and scalable synthetic methodologies. These bridged compounds exhibit high synthetic yields and enhanced energetic characteristics. Comprehensive structural elucidation and purity verification were performed by using multinuclear NMR (1H, 13C, 15N) spectroscopy, infrared (IR) spectroscopy, elemental analysis (EA), high-resolution mass spectrometry (HRMS), thermogravimetric analysis, and differential scanning calorimetry (TGA-DSC) studies. The molecular and crystal structures of compounds 2 and 4 were further confirmed by single-crystal X-ray diffraction analysis. Compound 3 emerged as a promising thermally stable secondary explosive, showing mechanical insensitivity (IS = 40 J, FS = 360 N) and high detonation metrics (VOD = 7712 m s–1; DP = 23.78 GPa), outperforming TNT and HNS. These results highlight the potential nature of this bridged oxadiazole motif for next-generation secondary explosives that balance sensitivity, thermal stability, and performance.