Electronic structure of boron and nitrogen doped isomeric graphene nanoflakes

Abstract Electronic properties of nitrogen and boron doped isomeric graphene nanoflakes have been explored using dispersion corrected B3LYP functional and CASSCF methods. The most thermodynamically stable isomers of nitrogen and boron doped systems contain phenalene and azulene motifs substituted in positions 7 and 9, respectively. Nitrogen doping promotes nanoflake planarity, increases singlet-triplet gap and a band gap, while boron doping promotes dome shaped nanoflake geometry, polyradicalic ground state, reduces singlet-triplet gap. Isomeric nanoflakes are less sensitive to doping compared to graphene nanoflakes. Nitrogen is a weak n type dopant for isomeric nanoflakes, while boron cannot be considered as a p type dopant. This effect is explained by non-uniform electron density distribution in pristine isomeric nanoflakes as compared to graphene nanoflakes.