Spherical Congeners of Polyaromatic Compounds Approaching C₂₀- and C₆₀-Fullerene-Type Structures

A series of three symmetric, hollow spherical, and shape-persistent molecular organic cages analogous to C₂₀ and C₆₀ were examined by computational modeling, analyzing structural elements, strain indicators, and physical properties relevant for potential applications. The compounds are covalent aromatic cages based on 1,3,5-substituted benzene nodes linked by para-phenylene or para-pyrenylene-connectors, with diameters varying from 2.3 to 4.2 nm. The apertures in the cage interior are varied by virtue of the cage type (C₂₀- or C₆₀-type cage) and the linear connectors placed between the C₆H₃-units. NBO and MESP analyses indicate the presence of electrophilic and nucleophilic sites in the molecular skeleton. In the cages with the phenylene-connectors, the HOMO-LUMO gaps are close to 4.0 eV. In the cage coated with an enlarged polyaromatic spacer (pyrene-unit), the gap is reduced by approximately 0.4 eV.