Ngn (Ng= Ne, Ar, Kr, Xe, and Rn; n=1, 2) encapsulated porphyrin-like porous C24N24 fullerene: A quantum chemical study

This study focused on the theoretical viability of Ngn@C24N24 (Ng = Ne, Ar, Kr, Xe, and Rn; n = 1, 2) complexes using density functional theory at the computational level of omega B97X-D/def2-TZVP. Thermodynamic and kinetic stabilities of these complexes have been evaluated by calculating the interaction energy of Ng atoms encapsulated C24N24 cage (Delta Eint), and the corresponding dissociation energy barrier (Delta G double dagger), respectively. The obtained results predict that although these complexes are thermodynamically unstable compared to their dissociation into free Ng atoms and the bare C24N24 cage, but once formed, they are protected by the activation energy barrier of the corresponding dissociation process. Furthermore, natural population analysis (NPA) and topological analysis of the electron density have been employed to investigate the nature of Ng-Ng and Ng-cage interactions. The results demonstrate that these interactions are highly significant compared to similar cases in the free state; and the amounts of energy of the interaction gradually increases as the Ng atom becomes heavier. Surprisingly in the Kr2@C24N24 complex the Kr-Kr bond is somewhat covalent in nature relative to non-bonded interaction in Kr2 free dimer.