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

Photoinduced electron and energy transfers between ZnTPP-d(20) (TPP; tetraphenylporphyrin) and fullerene (C-60) 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-d(20) cation radical (ZnTPP+) and the lowest excited triplet state of C-60. Quantitative analysis of the time-evolution of the C-3(60) and ZnTPP+ signals demonstrates that electron transfer occurs from (ZnTPP)-Zn-3 to C-60 and ZnTPP to C-3(60) and triplet-triplet energy transfer from (ZnTPP)-Zn-3 to C-60. The induced absorptive polarizations of the C-3(60) and ZnTPP+ signals are explained by electron spin polarization transfer. (C) 1998 Published by Elsevier Science B.V. All rights reserved.