Investigation on Stabilities and Spectroscopy of C80O2 Based on C80 (D5d) Using Density Functional Theory

The relative stabilities of the 17 possible isomers for C80O2 based oil C-80 (D-5d) were studied using Becke three parameters Plus Lee, Yang, and Parr's (B3LYP) method and 6-31G (d) basis set in density functional theory. The most stable geometry of C80O2 was predicted to be 23,24,27,28-C80O2 (A) with annulene-like structures, where the additive bonds are those between two hexagons (6/6 bonds) near the equatorial belt of C-80 (D-5d). Electronic spectra of C80O2 isomers were calculated based on the optimized geometries using intermediate neglect of differential overlap (INDO) calculation. Compared with those of C-80 (D-5d), the first absorptions in the electronic spectra of C80O2 are blue-shifted owing to the wide energy gaps. C-13 nuclear magnetic resonance spectra and nucleus independent chemical shifts of the C80O2 isomers were computed at B3LYP/6-31G level. The chemical shifts of the bridged carbon atoms in the epoxy structures of C80O2 compared with those of the bridged carbon atoms in the annulene-like structures are changed upfield. Generally, the isomers with the annulene-like structures of C80O2 are more aromatic than those with the epoxy structures. The addition of the oxygen atoms near the pole of C-80 (D-5d) is favorable to improving the aromaticities of C80O2. (C) 2008 Wiley Periodicals, Inc. Int J Quantum Chem 109: 693-700, 2009