Tailoring Azo-Bridged Nitropyrazoles: Enhancing Energy Thresholds through Complete Functionalization

The design of high-energy density energetic materials (HEDMs) and the exploration of energy limits have long been prominent research areas, presenting both significant opportunities and challenges. In this study, we report the synthesis of 1,2-bis(4-azido-3,5-dinitropyrazolyl) diazene (BLG-101) utilizing an energetic block design strategy based on a long nitrogen chain. BLG-101 exhibits a high crystal density of 1.924 g·cm^-3, with a measured density of 1.89 g·cm^-3, and demonstrates excellent enthalpy of formation alongside favorable thermal stability. Notably, BLG-101 showcases exceptional detonation performance, achieving a detonation velocity (V_D) of 9800 m·s^-1 and a heat of detonation (Q) of 6893 kJ·kg^-1, surpassing those of the classical high-energy compound CL-20, which has a V_D of 9445 m·s^-1 and a Q of 6134 kJ·kg^-1. However, BLG-101 has a higher mechanical sensitivity (IS = 3.6 J, FS = 32 N) than CL-20 (IS = 4 J, FS = 48 N). The integrated design approach, which synergistically combines nitro, azide, and elongated nitrogen chain structures within a pyrazole framework, significantly enhances the energetic performance of nitropyrazole compounds. This innovative strategy not only overcomes the current energy limitations associated with nitropyrazole derivatives but also provides a novel pathway for the design and synthesis of new energetic compounds with high energy density.