Optical spectra of diels-alder adducts of C60

The UV-Vis spectra of Diels-Alder adducts of C60 show characteristic differences with respect to the spectra of isolated C60. New bands appear between 400 and 500 nm, as well as at around 700 nm. In order to explain the origin of these bands we performed quantum chemical calculations for model molecules: C60H2n (n=1,2,3). The upper bands correspond to singlet-singlet transitions while the lowest energy band can originate only from a triplet level and spin dependent interactions should be responsible for this excitation. Symmetry arguments indicate that such transitions remain forbidden for pure C60.