Photoinduced Energy and Electron Transfer in Phenylethynyl-Bridged Zinc Porphyrin-Oligothienylenevinylene-C60 Ensembles

Donorbridgeacceptor triad (Por-2TV-C60) and tetrad molecules ((Por)2-2TV-C60), which incorporated C60 and one or two porphyrin molecules that were covalently linked through a phenylethynyl-oligothienylenevinylene bridge, were synthesized. Their photodynamics were investigated by fluorescence measurements, and by femto- and nanosecond laser flash photolysis. First, photoinduced energy transfer from the porphyrin to the C60 moiety occurred rather than electron transfer, followed by electron transfer from the oligothienylenevinylene to the singlet excited state of the C60 moiety to produce the radical cation of oligothienylenevinylene and the radical anion of C60. Then, back-electron transfer occurred to afford the triplet excited state of the oligothienylenevinylene moiety rather than the ground state. Thus, the porphyrin units in (Por)-2TV-C60 and (Por)2-2TV-C60 acted as efficient photosensitizers for the charge separation between oligothienylenevinylene and C60.