Electronic states of organic radical-functionalized graphenes and fullerenes: Density functional theory (DFT) study

Structures and electronic states of the aryl radical functionalized graphene have been investigated by means of density functional theory (DFT) method to elucidate the effects of functionalization on the electronic states of graphene (GR). Also, the reaction mechanism of aryl radical with GR was investigated. The benzene, biphenyl, pterphenyl, and p-quaterphenyl radicals (denoted by (Bz)n (n=1-4), where n means numbers of benzene rings in aryl radical) were examined as aryl radicals. The DFT calculation of GR-(Bz)n (n=1-4) showed that the aryl radical binds to the carbon atom of GR, and a C-C single bond was formed. The binding energies of aryl radicals to GR were calculated to be ca.6.0 kcal mol-1 at the CAM-B3LYP/6-311G(d,p) level. It was found that the activation barrier exists in the aryl radical addition: the barrier heights were calculated to be 10.0 kcal/mol. The electronic states of GR-(Bz)n were discussed on the basis of theoretical results.