Molecular design of functionalized fullerenes and graphenes: Density functional theory (DFT) study

Functionalized fullerene and graphene are known as high-performance molecular devices. In the present study, the structures and electronic states of the alkyl radical functionalized graphene (GR) and fullerenes (C
₆₀
) have been investigated by means of density functional theory (DFT) method to elucidate the effects of functionalization on the electronic states of carbon materials. Also, the reaction mechanism of alkyl radical with C
₆₀
(or GR) was investigated. The methyl, ethyl, propyl and butyl radicals (denoted by n=1-4, where n means number of carbon atoms in alkyl radical) were examined as alkyl radicals. The DFT calculation showed that the alkyl radical binds to the carbon atom of C
₆₀
in the on-top site, and a strong C-C single bond was formed. The binding energies of alkyl radicals to C
₆₀
were distributed in the ranges 31.8-35.1 kcal/mol at the CAM-B3LYP/6-311G(d,p) level. It was found that the activation barrier exists before the alkyl addition: the barrier heights were calculated to be 2.1-2.8 kcal/mol.