Spherical double electric layer structure of C 20F 20 and its endohedral complexes X@C 20F 20 (X = O 2−, S 2−, Se 2−)

Abstract

The structures and stabilities of cage C 20F 20 and its endohedral complexes X@C 20F 20 (X = O 2−, S 2−, Se 2−) were determined at the B3LYP/6-31G(d) levels of density functional theory (DFT). It is found that cage C 20F 20 ( I h) possesses of a distinct C δ+–F δ− spherical double electric layer, and the adiabatic electron affinity ( EA ad) of host cage is higher than that of isolated O atom (2.63 vs. 1.46 eV). This suggests the C 20F 20 cage can selectively trap and stabilize the capsulated spherical anions. The calculations predict that all guest species are minima at the cage center and the corresponding X@C 20F 20 ( I h) complexes have negative inclusion energies (Δ E inc) and thermodynamic parameters (Δ Z). The amount of charge that is being transferred from the encapsulated anions to the cage increases with the atomic radius, i.e., from O 2− (∼54%), S 2− (∼114%) to Se 2−(∼130%), and such a novel model of cage may have practical uses as potential and electrical building units of nanoscale materials.