Studies on the Electronic Structures and Spectra of C78(CH2)3

摘要

The structures and spectra of 20 possible isomers of C78(CH2)3 have been studied by using AM1, INDO/CIS and DFT methods. The results show that the most stable isomer is 1,2,3,4,5,6-C78(CH2)3 (A) with annulene structures, where three -CH2 groups are added to the 6/6bonds located at the same hexagon passed by the shortest axis of C78(C2v). Compared with that of C78(C2v), the first absorption in the electronic spectrum of C78(CH2)3 (A) is blue-shifted because of its wider LUMO-HOMO energy gap. While the IR frequencies of the C-C bonds on the carbon cage are red-shifted owing to the formation of annulene structures and the extension of the conjugated system. The chemical shifts of the carbon atoms in 13C NMR spectra are moved upfield upon the addition.