What are the roles of N3 and N5 rings in designing polynitrogen molecules?

Abstract

A series of polynitrogen molecules composed by multiple cyclic-N₃ and/or cyclic-N₅ are systematically investigated by using DFT and MP2 methods. It is found that all energetically favored structures appear with a corner to corner connection between two rings for the cyclic-N₃ and/or the cyclic-N₅. Furthermore, straight interaction between the N₃-rings would decrease the stability of cyclic-N₃ relative to the cyclic-N₃ radical and thus not favor the formation of a stable structure containing multiple cyclic-N₃, while the interaction between the N₅-rings can improve the stability of cyclic-N₅ and tend to produce a stable structure composed by multiple cyclic-N₅. For the stable structure consisting of cyclic-N₃ and cyclic-N₅, the charge is transferred from cyclic-N₃ to cyclic-N₅, facilitating the stability of N₅, and the attacked site of the structure by the radicals is analyzed by condensed Fukui function. Finally, the stabilities of the structures N₃(N₅)₃ and N₅(N₅)₅ are investigated and demonstrated to be attributed to the charge transfer and the coordination number of N₃-ring and N₅-ring.