Regioisomeric functionalization of azo-bridged nitropyrazoles: Pushing the density limit of catenated nitrogen systems

Fully energetic functionalization of catenated nitrogen systems is highly challenging due to the lack of incorporation methodology. In this work, two catenated nitrogen N6 structures containing six nitro groups, i.e., (E)-1,1′-bis [5-Nitroamide-3,4-dinitro-1H-pyrazole] diazene (N-N6A) and its regioisomer (E)-1,1′-bis [4-Nitroamide-3,5-dinitro-1H-pyrazole] diazene(N-N6B) were designed and synthesized. Despite the same chemical formula and azo functionality, N-N6B exhibits better overall performance than N-N6A. Meanwhile, N-N6B has the highest density with excellent detonation performance (d = 1.94 g cm−3, Dv = 9440 m s−1, and P = 39.6 GPa) among the reported long-catenated nitrogen atom chains, indicating the potential for high energy materials. Particularly, as the precursors of N-N6A and N-N6B, the mechanical sensitivities of N6A and N6B (N6A, IS = 11 J, FS = 160 N; N6B, IS = 14 J, FS = 240 N) are apparently superior to that of literature long nitrogen-chains energetic material. The different performance of these compounds highlights the effect of the regioisomeric functionalization on designing advanced energetic materials.