Xuguang Wen^a, Xin Ren^b and Shi Wu ^a,*

^a Department of Chemistry, Zhejiang University, Hangzhou 310027, China
^b Department of Pharmacy, Zhejiang University, Hangzhou 310027, China
* Corresponding author: E-mail: wushi@zju.edu.cn
tel: 8657188206529; fax: 8657188206529

Abstract
The electronic structures and stabilities of the nine possible isomers of C₈₀CH₂ based on C₈₀(D_5d) 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(D_5d). Compared with those of C₈₀(D_5d), 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.

Keywords: C₈₀CH₂, B3LYP/6-31G, electronic spectra, ¹³C NMR, NICS.