EPR STUDIES OF THE EXCITED TRIPLET-STATES OF C60O AND C60C2H4N(CH3) FULLERENE DERIVATIVES AND C-70 IN TOLUENE AND POLYMETHYLMETHACRYLATE GLASSES AND AS FILMS

The EPR spectra of excited tripler stares of two fullerene derivatives , C60O and C60C2H4N(CH3), in the glassy matrices of toluene and of pol ymethylmethacrylate (PMMA) and as films were examined at low temperatu re and the magnetic parameters were measured. In films, species with z fs parameters smaller than those in toluene were found and they were a ssigned to triplet excitations visiting more than one molecule in the crystallites that form the film. When C60C2H4N(CH3) was excited in PMM A grown by in situ thermal polymerization a new triplet species was or iginated characterized by a dipolar splitting constant D about three t imes larger than that measured in toluene. Evidence was gained that su ch species participates to cross-linking in the polymer. The effect of PMMA matrix on the molecular dynamics of C-3(70) was also investigate d. It was found that a dynamical model holds based on the pseudorotati on of the molecule around the axis of larger dipolar splitting. Motion is activated with activation energy of 210+/-50 cm(-1) a value compar able with that obtained for pseudorotation of C-3(70) in cyclohexane.