ENERGY AND CHARGE-TRANSFER DYNAMICS IN SELF-ORGANIZED MULTIMOLECULAR ARRAYS

The main kinetic parameters of the nonradiative singlet-singlet energy transfer and the charge separation have been studied for well-defined supramolecular arrays with controllable number and photophysical prop erties of subunits in methylcyclohexane in the temperature range of 77 -300 K (cw, picosecond time-resolved fluorescence spectroscopy and fem tosecond pump-probe kinetic data). The arrays formation is based on co valently linked Zn-porphyrin dimers with or without electron accepters (quinone, anthraquinone, pyromellitimide) and the noncovalent self-as sembling with pyridyl substituted tetrapyrrolic extra-ligands (porphyr ins, chlorins and tetrahydroporphyrins, fluorinated tetraphenylporphyr ins). It has been found that the competition between the energy transf er(within less than or equal to 10 ps) and charge transfer (within 300 fs-700 ps) processes in the systems under consideration depends on th e structure, spectral and redox properties of interacting subunits and may be driven by the distance, temperature and solvent polarity. The possible mechanisms of the excited S-states quenching in the complexes (including 'superexchange' model) are discussed. (C) 1998 Elsevier Sc ience B.V. All rights reserved.