MAGNETIC FIELD EFFECTS ON THE DECAY RATE OF TRIPLET BIRADICAL OR RADICAL PAIR GENERATED FROM PHOTOINDUCED ELECTRON TRANSFER IN FULLERENE-PHENOTHIAZINE SYSTEMS

摘要

Transient absorption and fluorescence spectra of fullerene (C_(60))-phenothiazine (PH) linked compounds indicated that the photoinduced intramolecular electron transfer occurred in benzonitrile, while not in benzene. The results are due to solvent effects on energy levels of the photogenerated biradical. In benzonitrile, the decay rate of the biradicals was retarded in the presence of magnetic fields. The decay rate constant decreased quickly with increasing the magnetic field and became constant above ca. 0.2 T. The magnetic field effects verified that the triplet biradical was generated from the intramolecular electron transfer from PH to the triplet excited state of C_(60) (~3C_(60)*). In case of nonlinked compounds, the intermolecular electron transfer from PH to ~3C_(60)* occurred and generated the triplet radical pairs, but no magnetic field effects were observed.