Intramolecular photoinduced processes of newly synthesized dual zinc porphyrin-fullerene triad with flexible linkers

Zinc porphyrin-fullerene-zinc porphyrin triad, in which two zinc porphyrin (ZnP) moieties and a fullerene (C,,) moiety are linked by flexible bonds and which is intended to be a working model of the photosynthetic antenna-reaction centre, has been newly synthesized. Its photophysical properties have been investigated by both time-resolved emission and transient absorption techniques. Excitation of the zinc porphyrin moiety of the triad induced charge separation, generating the radical ion pair, in which the electron localizes on the C, moiety and the hole localizes on the zinc porphyrin moiety. In polar solvents, the charge-separated states decayed with lifetimes of 300600 ns returning to the ground state. Compared with ZnP-C-60 dyad, ZnP-C-60-ZnP triad showed longer lifetimes for the radical ion pair due to the conformation of the two ZnP moieties. The effects of the coordinating reagents on the zinc atom have been studied, with the expectation of conformational change of the two ZnP moieties with respect to C-60. Copyright (c) 2006 Society of Porphyrins & Phthalocyanines.