Photoinduced electron transfer processes in fullerene–organic chromophore systems

The review concentrates on supermolecular electron-donor–acceptor systems composed of porphyrin dyes covalently linked to fullerene. These model systems are of a great importance not only in optoelectronic technologies but also in the life sciences in relation to respiration, photosynthesis and photomedicine. Results of studies of supermolecular systems composed of zinc porphyrin and its dyad covalently linked to one fullerene or two fullerene molecules (in chloroform solution and in the form of Langmuir–Blodgett layers on a gold substrate) are presented to illustrate the spectroscopic properties and electron transfer processes taking place in such systems. Some simpler models of donor–acceptor ensembles are also presented. Electronic absorption and fluorescence supported by reflectance–absorption in infrared and electron spin resonance spectroscopies as well examination of light-induced current generated in photoelectrochemical cells were used to follow the interactions, radiative and non-radiative processes accompanied with electron transfer from an electron donating species to an electron acceptor. The same methods could provide information on modification of the electronic structure of the systems. The observed changes in absorption and fluorescence quenching of porphyrins in the presence of fullerene have evidently shown charge redistribution both upon porphyrins linkage to fullerene and upon deposition of the systems on gold substrate resulting from the interaction between the organic layers and the solid. The results reported in this paper prove the donor–acceptor character of the zinc porphyrin–fullerene samples and influence of fullerene on dye photoactivity in the systems.