Pulsed and cw-time-resolved EPR studies of photoinduced electron transfer between zinc(II) porphyrin and fullerene

Photoinduced electron and energy transfers between ZnTPP-d20 (TPP; tetraphenylporphyrin) and fullerene (C60) were studied in benzonitrile solution at room temperature by means of pulsed-Fourier transform and cw-time-resolved EPR. Two kinds of EPR signals were observed with absorptive spin polarizations and assigned to those of the ZnTPP-d20 cation radical (ZnTPP+) and the lowest excited triplet state of C60. Quantitative analysis of the time-evolution of the 3C60 and ZnTPP+ signals demonstrates that electron transfer occurs from 3ZnTPP to C60 and ZnTPP to 3C60 and triplet–triplet energy transfer from 3ZnTPP to C60. The induced absorptive polarizations of the 3C60 and ZnTPP+ signals are explained by electron spin polarization transfer.