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

The variation of different heterocyclic ring bridges from the bis-12,4-oxadiazoles in A to the bis-1,3,4-oxadiazoles in B and then to the bis-1,2,4-triazoles in C gives rise to an order of increasing heat resistance ( A (317 °C) < B (368 °C) < BPT-2 (425 °C)). • A novel molecule BPT-2 with ultrahigh heat resistance was synthesized. • The superior thermostability of BPT-2 is rarely reported. • A strategy of introducing energetic bis-1,2,4-triazoles bridges was developed. • The correlations between the structure and properties were investigated. 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-NO 2 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.