Density Functional Theoretical Study of Polynitrogen Compounds N₅⁺Y⁻ (Y=B(CF₃)₄, BF₄, PF₆ and B(N₃)₄)

The structures and the stabilities of polynitrogen compounds N₅⁺Y⁻ [Y=B(CF₃)₄, BF₄, PF₆, and B(N₃)₄], as the potential high energy density compounds, have been investigated at the B3LYP/6-31G(d,p) and B3LYP/6-311+G(d,p) levels. On the basis of our geometry optimization calculations, the structural properties of the N₅⁺Y⁻ compounds are discussed, and it is found that the combination of the N₅⁺ cation and the Y⁻ anions leads to distortion of the structures of the Y⁻ anions. Based on the TS calculations for the N₂-loss dissociations of the N₅⁺Y⁻ compounds, the stabilities of these compounds are discussed, and the following conclusion can be drawn that among the four compounds, N₅⁺B(CF₃)₄⁻ is the most stable one and N₅⁺B(N₃)₄⁻ is the most unstable, and the relative stability of these compounds is always consistent using different basis sets. From these discussions, it is revealed that there are close correlations between the stuctrual distortions of the Y^? anions and the stabilities of the N₅⁺Y⁻ compounds, and between the nitrogen content in the compounds and the stabilities of the N₅⁺Y⁻ compounds.