Triplet-EPR spectroscopy on the Diels-Alder adduct of C60 and 4,5-dimethoxy-o-quinodimethane in frozen solution

Pulsed-EPR spectroscopy was used to study a modified C60 molecule (1) in its photoexcited triplet state. The analysis of the triplet EPR lineshape shows a break of the high symmetry of the lowest populated triplet state of C60 due to the modification of the C60 unity. The reported temperature dependence of the spectra is influenced by relaxation effects. Lineshape simulations based on a triplet Hamiltonian including anisotropic T1/T2 relaxation were performed. The results are discussed in relation to the behaviour of pure 3C60.