Construction of Symmetric Energetic Compounds with Lower Sensitivity via Integration of Flexible Chains

High-energy-density materials (HEDMs) have made significant progress in defense and space applications, but they still confront the challenges of unsatisfactory safety, sensitivity, and chemical applicability. In this work, a strategy to synthesize symmetric energetic materials by introducing flexible chains (−CH₂- or −CH₂CH₂−) is reported based on 5-azido-3-nitro-1H-1,2,4-triazole 1. N,N′-Methylene bridged compound 2 and N,N′-ethylene bridged compound 3 are successfully obtained through a one-step synthesis with high yield. The introduction of flexible chains significantly reduced the mechanical sensitivity of the two compounds. This change can be attributed to the synergistic effects of several factors, including the formation of hydrogen bonds, reduced oxygen balance, and variations in the ESP of the molecular surface. As a result, the bridged compound 2 (IS = 15 J, FS = 360 N) and compound 3 (IS > 40 J, FS > 360 N) exhibit lower sensitivity compared to the monocyclic functional integrated compound 1 (IS = 5 J, FS > 42 N). The detonation velocities of compounds 2 and 3 are 8439 and 7979 m·s^-1, respectively.