Theoretical characterization of a series of N5-based aromatic hyperhalogen anions

Abstract

Hyperhalogens are a class of highly electronegative molecules whose electron affinities even exceed those of their superhalogen ligands. Such species can serve as new oxidizing agents, biocatalysts, and building blocks of unusual salts, and hence are important to the chemical industry. Utilizing stable N₅⁻ as the ligand, a series of aromatic hyperhalogen anions, namely mononuclear M(N₅)_k+1⁻ (M = Li, Be, B) and dinuclear M₂(N₅)_2k+1⁻ (M = Li, Be), have been reported here for the first time. Calculation results based on the density functional theory revealed that all the N₅⁻ subunits preserve their structural and electronic integrity as well as aromatic characteristics in these anions. Especially, these anionic molecules exhibit larger vertical electron detachment energies (6.76–7.86 eV) than that of the superhalogen ligand N₅⁻, confirming their hyperhalogen nature. The stability of these studied anions is guaranteed by their large HOMO–LUMO gaps, and positive dissociation energies of predetermined fragmentation pathways. We hope this work will not only provide evidence of a new type of hyperhalogen molecule but also stimulate more research interest and efforts in the amazing superatom realm.