Relative Stability and Spectroscopic Regularity of C80O Based on C80(D5d).

The relative stabilities of the nine possible isomers for C80O based on C80(D5d) were investigated via density function theory (DFT) at B3LYP/6-31G(d) level. The most stable geometry of C80O is predicted to be 23,24-C80O, where an annulene-like structure is formed. The stretching vibration frequencies of the C=C bonds in the IR spectrum of C80O compared with those of the C=C bonds in the IR spectrum of C80(D5d) are basically blue-shifted. The signals of the bridged carbon atoms in the NMR spectrum of C80O, computed at B3LYP/6-31G level, are changed upfield compared with those of the correspoding carbon atoms in the NMR spectrum of C80(D5d). The anti-aromaticity of rings in C80O relative to that of the corresponding rings in C80(D5d) is decreased according to the NICS values at the dummy centers of these rings calculated at B3LYP/6-31G level. A hexagon in 21,22-C80O even shows a tendency of aromaticity.