Substituent‑controlled energy‑sensitivity trade‑off in (E)-1,2-bis(tetrazolo[1,5-d][1,2,3,4]tetrazin-7(1H)-yl)diazene derivatives.

CONTEXT: A series of (E)-1,2-bis(tetrazolo[1,5‑d][1,2,3,4]tetrazin-7(1H)-yl)diazene derivatives featuring extended nitrogen chains with 16-22 consecutive nitrogen atoms were designed and computationally assessed for both energetic characteristics and safety performances. Two nitro‑containing compounds, (E)-1,2-bis(1-nitrotetrazolo[1,5-d][1,2,3,4]tetrazin-7(1H)-yl)diazene (B2) and (E)-N-(7-((1-nitrotetrazolo[1,5-d][1,2,3,4]tetrazin-7(1H)-yl)diazenyl)tetrazolo[1,5-d][1,2,3,4]tetrazin-1(7H)-yl)nitramide (C3), with densities exceeding RDX, detonation velocities exceeding CL-20, detonation pressures close to CL-20, and predicted sensitivities lower than RDX, HMX, and CL-20, thus emerging as particularly promising high-energy low-sensitivity candidates. Frontier orbital analysis reveals that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) are primarily localized on the central skeleton, implicating this core in electronic transitions. Substituent groups narrow the HOMO-LUMO gap, and electrostatic potential maps indicate strongly polarized charge distributions. The energetic contribution of substituents follows the order of -NO2 > -NHNO2 > -N3 > -NH2 > -NHNH2, with the safety ranking being exactly the reverse. Collectively, this work provides a novel and viable strategy for the rational design of insensitive high‑energy materials with long catenated nitrogen chains. METHODS: Full geometry optimizations of all compounds were performed by B3LYP functional and 6-311G** basis set under DFT, as implemented by Gaussian 09 package. The enthalpy of formation of all compounds was derived from both isodesmic and atomization reaction paths. The detonation characteristics of these compounds were obtained by the Kamlet-Jacobs (K-J) equations, and the safety performance of these compounds was evaluated by impact sensitivity, which is measured by h50 value.