Electronic structure of hybrid pentaheptite carbon nanoflakes containing boron-nitrogen motifs.

The electronic structure of isomeric graphene nanoflakes (NFs) heavily doped with boron and nitrogen atoms has been explored. Dispersion-corrected B3LYP functional has been used for the geometry optimizations. A complete active space method has been used for the energy evaluations. Combined boron and nitrogen doping promotes polyradicalic antiferromagnetic ground states in the NFs and affects the nanoflake geometry. There is a charge transfer from boron to nitrogen atoms which increases with the doping level. This transfer does not involve carbon atoms. Combined doping reduces both the ionization potentials (IPs) and the electron affinities (EAs) of the NFs similar to nitrogen doping alone. Boron does not affect either IPs or EAs being neither n- nor p-type dopant for the isomeric graphene NFs. All hybrid NFs show a tendency to increase the band gaps with doping level, which is promoted by the increment of the bond length alternation with doping. Finally, the hole reorganization energies for the NFs were found to be lower than the electronic ones, positioning the hybrid NF as hole-transporting systems. Graphical Abstract Color coded natural charge differences between charged and neutral states. The excess of positive charge is green for cation radicals and the excess of negative charge is red in anion radicals.