Osnabrück 2002 – scientific programme

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SYBP: Biophotonik

SYBP 4: Postersitzung

SYBP 4.7: Poster

Thursday, March 7, 2002, 17:45–20:00, Schloss

Multistep photoinduced electron/hole transfer in nanoscale biomimetic models studied by time-resolved spectroscopy — •Zenkevich Eduard — Institute of Molecular and Atomic Physics, F. Skaryna Avenue 70, 220072 Minsk, Belarus — TU Chemnitz, Institute of Physics 122501, 09107 Chemnitz

Using static and time-resolved picosecond fluorescent and femtosecond pump-probe set-up, the dynamics of non-radiative relaxation processes (including charge separation and energy transfer) have been studied in the triads with controlable geometry prepared via non-covalent binding interactions of dipyridyl substituted tetrapyrrole extra-ligands (porphyrin, chlorin, tetrahydroporphyrin) with Zn-octaethylporphyrin dimers which, in its turn, are covalently linked to electron acceptors (quinone, pyromellitimide). It has been shown that the directionality and efficiency of the photoinduced charge separation is a function of redox and photophysical properties of interacting subunits as well on the solvent polarity and temperature. The strong quenching of the dimer S₁-state is due to energy and sequential electron transfer processes to the extra-ligand, which are faster than a slower electron transfer dimer→acceptor (toluene, 293 K). The extra-ligand S₁-state decay is governed by competing processes: a bridge mediated long-range superexchange electron transfer ligand→acceptor and photoinduced hole transfer ligand→dimer followed by superexchange electron transfer steps to low-lying CT states.