A density functional theory study on the electronic and adsorption characteristics of cyclo M9N9 (M = B and Al)

On the basis of experimental and theoretical calculations conducted for cyclo C₁₈, we predicted two novel inorganic cyclo M₉N₉ (M = B and Al) molecules. Because of the significant difference in electronegativity between M and N atoms, M-N bonds were ionic. Furthermore, the interaction of cyclo M₉N₉ with cyclopropylpiperazine (CPPP) was investigated. In cyclo M₉N₉, each M atom could adsorb one CPPP molecule. The CPPP molecules exhibited a preference to remain outside cyclo M₉N₉ molecules. Depending on the structural characteristics of CPPP molecules, the exciting part is that up to four CPPP molecules could be adsorbed on the exterior surface of cyclo M₉N₉. We calculated adsorption energies and analyzed the main structural parameters in the process. The research results indicated that adsorption on cyclo Al₉N₉ was energetically more favorable than that on cyclo B₉N₉. The cyclo M₉N₉ have considerable potential in the future. Graphical abstract.