Introduction of energetic bis-1,2,4-triazoles bridges: A strategy towards advanced heat resistant explosives

Abstract

Over the last few decades, the research for energetic materials with ultrahigh heat resistance and good energy level has been a highly severe challenge. In this study, a novel heat-resistant compound, 5,5′-bis(4-nitro-1H-pyrazol-3-yl)−2H,2′H-3,3′-bis-1,2,4-triazoles (BPT-2), was developed through the introduction of an energetic bis-1,2,4-triazoles bridge between two nitropyrazole moieties. This neutral molecule shows an ultrahigh thermal decomposition temperature of 425 °C that is extremely rare in the field of heat resistant explosives, enhanced energy level (detonation velocity: 7503 m s−1) superior to that of the extensively used heat resistant explosive HNS (7164 m s−1), insolubility in water and a facile three-step reaction. These prominent properties of BPT-2 support it as an advanced heat resistant explosive with great promise. Furthermore, an in-depth investigation on the influence of different heterocyclic ring bridges (i.e., bis-1,2,4-oxadiazoles in A, bis-1,3,4-oxadiazoles in B and bis-1,2,4-triazoles in BPT-2) on the thermal stability of the corresponding target compounds was performed.The result indicates that the preferable aromaticity and C-NO2 bond strength of bis-1,2,4-triazoles contribute to the excellent thermostability of BPT-2 in comparison to those of bis-1,2,4-oxadiazoles and bis-1,3,4-oxadiazoles analogues. This work is anticipated to prompt more research on the promising strategy of introducing energetic bis-1,2,4-triazoles bridges in the molecular design and offers guidance for the development of advanced heat resistant explosives.