Direct observation of electron spin polarization transfer in triplet-triplet energy transfer between porphyrins and fullerene in fluid solution

Time-resolved electron paramagnetic resonance (EPR) has been used to investigate electron spin polarization transfer in triplet-triplet (T-T) energy transfer between porphyrins (MOEP and MTPP; M = H-2, Zn) and fullerene (C-60) in toluene solution. EPR spectra of excited triplet (T-1) states of both a donor (porphyrins) and an acceptor (C-60) were directly observed. The induced spin polarizations of T-1 C-60 were found to be the same as those of T-1 porphyrins. From the analyses of time-profiles of both tripler signals, it was shown that T-1 polarizations of porphyrins are transferred to T-1 fullerene with conservation of spin polarizations via T-T energy transfer. (C) 1998 Elsevier Science B.V.