The structures and UV spectra of both of the isomers for the additive products HC60[CH2C(CH3)=CH2] resulted from C60 and CH2=C(CH3)CH2 MgCl have been investigated by the series of INDO methods. It is illustrated that the 1,2-additive product is of Cs symmetry and 1,4-additive product is of C1 symmetry, furthermore the total energy of the 1,2-isomer is lower than that of the 1,4-isomer thus the former is easier to obtain. The bond between CH2=(CH3)CH2 and C60 in the product belongs to the polar covalent bond and the electronic transmmission from the former to the latter has happened. Based on the optimised geometry, the UV spectra of both of the isomers have been calculated and are in agreement with the experimental results. Meanwhile the theoretical assignment for the electronic transition has been performed and the red shift of the UV peaks has been rationalized.

Key words: ULTRAVIOLET SPECTROPHOTOMETRY, ELECTRONIC STRUCTURE, ADDITION REACTION, INTERMEDIATE NEGLECT OF DIFFERENTIAL OVERLAP APPROXIMATION (IND, FULLERENES