DFT study on stability and spectroscopy of C84O2 based on C84 (D2)

The equilibrium geometries of the 20 possible isomers of C84O2 were studied using density function theory (DFT). The relative energies of the C84O2 isomers were calculated at the single point on B3LYP/6-31G(d) level. The most stable geometry of C84O2 at the ground state has been found to be 2,3,12,13-C84O2, where the oxygen atoms are added to the same hexagon and annulene-like structures are formed. Based on the optimized geometries at B3LYP/6-31G level, the 13C chemical shifts and nucleus independent chemical shifts (NICS) of the C84O2 isomers were calculated at B3LYP/6-31G level. The chemical shifts of the bridged carbon atoms in 2,3,12,13-C84O2 compared with those of the corresponding carbon atoms in C84 (D2) are changed upfield. The isomers of C84O2 with the annulene-like structures are more aromatic than those with the epoxy structures.