[5,5]-Fused Heterocycle-Bridged Bistetrazoles Enable High-Energy and Insensitive Nitrogen-Rich Materials

Constructing bridged bistetrazole frameworks is an established strategy for tuning the performance and safety of nitrogen-rich energetic materials. Here, we introduce a rigid [5,5]-fused heterocycle as a structural bridge to access a family of bistetrazole-based energetic compounds (2, 5, 6, and 2a-2d) through a concise and efficient synthetic route. These compounds exhibit high density (ρ = 1.79-1.90 g cm^-3), excellent thermal stability (T_d = 181-354°C), and favorable mechanical insensitivity (IS = 16-30 J; FS = 240-360 N). Notably, the energetic salts 2c (D_v = 9285 m s^-1) and 2d (D_v = 9551 m s^-1) outperform the benchmark explosive RDX (D_v = 8814 m s^-1). These results demonstrate that [5,5]-fused-ring bridging provides an effective design principle for achieving synergistic enhancement of energy density and safety, offering a powerful platform for the development of next-generation energetic materials.