Theoretical studies on the long nitrogen chain structure and the constructing mechanism of a catenated N₁₁ cation

The long nitrogen chain compound, as a potential energetic material, exhibits remarkable explosive properties. Therefore, it is imperative to conduct an in-depth investigation into its structural characteristics and construction mechanism. Herein, a catenated N₁₁ cation was theoretically studied. It has a relatively low sensitivity and a possible decomposition mechanism triggered by the weak N−N bonds, which agrees well with the experimental results. We proposed a synthesis mechanism involving the N−N bond formation and the two-step proton shift with energy barriers of 6.63, 57.53, and 43.81 kcal mol⁻¹, respectively. The proton shift effectively strengthens the newly formed N−N bond while maintaining structural balance. Furthermore, a comparative reaction was studied to highlight the value of utilizing heterocyclic nitrogen structures for developing long nitrogen chain energetic compounds. These results give theoretical support for developing new high energy density materials and all-nitrogen energetic materials.