1,3,4-Oxadiazole Bridges: A Strategy to Improve Energetics at the Molecular Level

Many energetic materials synthesized to date have limited applications because of low thermal and/or mechanical stability. This limitation can be overcome by introducing structural modifications such as a bridging group. In this study, a series of 1,3,4-oxadiazole-bridged furazans was prepared. Their structures were confirmed by ¹ H and ¹³ C NMR, infrared, elemental, and X-ray crystallographic analyses. The thermal stability, friction sensitivity, impact sensitivity, detonation velocity, and detonation pressure were evaluated. The hydroxylammonium salt 8 has an excellent detonation performance (D=9101 m s^-1 , P=37.9 GPa) and insensitive properties (IS=17.4 J, FS=330 N), which show its great potential as a high-performance insensitive explosive. Using quantum computation and crystal structure analysis, the effect of the introduction of the 1,3,4-oxadiazole moiety on molecular reactivity and the difference between the sensitivities and thermal stabilities of mono- and bis-1,3,4-oxadiazole bridges are considered. The synthetic method for introducing 1,3,4-oxadiazole and the systematic study of 1,3,4-oxadiazole-bridged compounds provide a theoretical basis for future energetics design.