Photoinduced Electron Transfer in Ferrocene-Porphyrin Oligomer-Fullerene Systems

摘要

A Meso-,meso-linked porphyrin trimer [(ZnP)3] as a light-harvesting chromophore has been incorporated for the first time into a photosynthetic electron transfer model including ferrocene (Fc) as an electron donor and fullerene (C60) as an electron acceptor to construct the ferrocene-meso,meso-linked porphyrin trimer-fullerene system (Fc(ZnP),-C60). Photoirradiation of Fc-(ZnP),-C60 results in photoinduced electron transfer from the singlet excited state of the porphyrin trimer [1(ZnP),] to the C60 moiety to produce the porphyrin trimer radical cation-Cradical anion pair, Fc-(ZnP)3-C6 Subsequent formation of the final charge-separated state, i.e., Fe-(ZnP),-C60–, was confirmed by the transient absorption spectra observed in the laser flash photolysis. The final charge-separated state decays obeying first-order kinetics with a lifetime of 0.53 s in DMF at 163 K. The lifetime is comparable to those of the natural bacterial photosynthetic reaction center and longer than that of any other multistep electron transfer model system. More importantly, the quantum yield of formation of the final charge-separated state (i.e.,.83) remains high despite of large separation distance of the Fe and Ca- radical ion pair. Such a high quantum yield results from the efficient charge separation through the porphyrin trimer, whereas the slow charge recombination is associated with the localized porphyrin radical cation in the porphyrin trimer.