Intramolecular integration of multiple heterocyclic skeletons for energetic materials with enhanced energy & safety.

The intramolecular integration of 1,2,5-oxadiazole, 1,2,4-oxadiazole and pyrazole skeletons affords energetic materials with well-balanced safety and energy level. [Display omitted] • An intramolecular integration of multiple heterocycles was developed. • The 1.2.5-oxadiazole and pyrazole skeletons were integrated into a molecule. • The overall performance of 6 approaches that of HMX. • The correlations between the structure and properties were investigated. The research for new generations of high explosives with the remarkable overall performance has always been a challenging task. Currently, the research priority of energetic materials is to explore new design strategies to balance and/or break the energy-safety limits. In this study, an intramolecular integration of various heterocyclic skeletons based on the unique superiority of each heterocycle was developed. By employing this approach, an advanced energetic molecule integrating 1,2,5-oxadiazole, 1,2,4-oxadiaozle and pyrazole skeletons, 5-(3,4-dinitro-1H-pyrazol-5-yl)-3-(4-nitro-1,2,5-oxadiazol-3-yl)-1,2,4-oxadiazole (6), was designed and prepared. The energy level (e.g., detonation velocity: 9094 m s−1) of 6 is approaching that of the extensively used high explosive, RDX (8801 m s−1), while its safety (impact sensitivity: IS = 24 J; thermal stability: T dec = 265 °C) are obviously superior to that of RDX (IS = 7.4 J; T dec = 204 °C). These favorable energetic properties demonstrate the outstanding overall performance of 6. Moreover, the variation of sensitivities and thermal stabilities were further investigated through the quantum chemistry methods based on the single-crystal data. Our study is anticipated to attract more in-depth study on the promising intramolecular integration approach and accelerate the development of the advanced energetic materials. [ABSTRACT FROM AUTHOR]