Driving the efficient construction and functional-group editing of 2-(1,2,4-triazole-5-yl)-1,3,4-oxadiazole-based high-energy compounds by a resonance-assisted hydrogen bonding strategy

Abstract

A resonance-assisted hydrogen bond (RAHB) is a special hydrogen bond where the donor and acceptor are connected via π-conjugated structures. Effected by π-electron delocalization, RAHBs usually exhibit partial covalent-bond properties. A quasi-aromatic ring constructed from RAHBs could, along with aromatic ones, further extend to a larger conjugated system, and the molecular density and thermal stability could be reinforced. Inspired by this design strategy, we prepared four bicyclic energetic molecules with RAHBs. The precursor 5-(3-amino-1H-1,2,4-triazol-5-yl)-1,3,4-oxadiazol-2-amine was synthesized via a more efficient approach. Two energetic products were obtained under different nitration conditions individually, without the burden of strenuous separation. In addition, two other energetic derivatives were prepared via the selective conversion of the diazo group. The four energetic molecules both feature intramolecular RAHBs via hydrogen atom transfer. Attributed to its more plentiful RAHBs, compound 6 exhibits the most outstanding detonation performance (D_v: 9042 m·s⁻¹ and P: 35.4 GPa) and thermal stability (T_d: 183 °C). Experimental results indicate that RAHBs could dramatically enhance the molecular density and thermostability of energetic materials, achieving a balance between energy and safety. Finally, a comparison of several dinitramino compounds further demonstrates the unlimited potential of RAHBs. This work not only achieved the synthesis and characterization of several energetic molecules via a simpler process but it also revealed the superiority of resonance-assisted hydrogen bonding when designing energetic materials.