Theoretical Studies on Stabilities and Spectroscopy of C80CH2

The electronic structures and stabilities of the nine possible isomers of C80CH2 based on C80(D5d) were studied using density function theory (DFT) at B3LYP/6-31G level. Based on the optimized geometries, the electronic spectra, IR and 13C NMR spectra of the isomers of C80CH2 were calculated using INDO/CIS, PM3 and B3LYP/6-31G methods, respectively. The most stable geometry of C80CH2 is predicted to be 27,28–C80CH2(A) with an annulene structure, where the additive bond is 6/6 bond near the equatorial belt of C80(D5d). Compared with those of C80(D5d), the first absorptions in the electronic spectra and main absorptions in the IR spectra of the stable C80CH2 isomers are red-shifted. The 13C chemical shifts of the bridged carbon atoms in the cyclopropane structures in comparison with those in the annulene structures are changed upfield. The aromaticities are better maintained in the annulene structures than cyclopropane structures according to the NICS values of C80CH2 at B3LYP/6-31G level.