A Study of the Aromaticity of the Heterofullerene C24–2nBnNn(n = 3 or 6) and C12N12 Isomers

Abstract

The global aromaticity of the heterofullerene C24–2nBnNn(n = 3 or 6) and C12N12 isomers formed from the initial C24 fullerene with D6 symmetry, has been investigated using both the topological resonance energy (TRE) and the percentage topological resonance energy (%TRE) methods. The local aromaticity was studied using the bond resonance energy (BRE) method. Analysis was made of the effects of the types, the numbers, and the arrangements of heteroatoms on the global and local aromaticity of the molecules under consideration. Our results obtained by the TRE and %TRE methods were compared with the nucleus independent chemical shift (NICS (0)) values at the cage center. We found that NICS(0) values were not suitable for estimating the global aromaticity of these compounds. It was expected that the inclusion of heteroatoms would decrease the antiaromaticity relative to the C24(D6) cage. Our BRE results show that the antiaromaticity is primarily related to the existence of highly reactive antiaromatic bonds in the molecule. We found that when a local structure within the cage had two nitrogen and one boron atom in the same pentagon ring, it played an important role in the global aromaticity of these compounds. Finally, we predicted the kinetic stability using the minimum BRE method.