Darmstadt 2008 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 25: Laseranwendungen (Spektroskopie)
Q 25.2: Talk
Tuesday, March 11, 2008, 16:45–17:00, 3H
Photo-induced electron and energy transfer in pyrene-flavin-phenothiazine dyad and triad complexes — •Javid Shirdel1, Alfons Penzkofer1, Roman Procházka2, Zhen Shen2, and Jörg Daub2 — 1Institut II - Physik, Universität Regensburg, D-93040 Regensburg — 2Institut für Organische Chemie, Universität Regensburg, D-93040 Regensburg
A pyrene-isoalloxazine dyad, a phenothiazine-phenylene-isoalloxazine dyad, and a pyrene-isoalloxazine-phenothiazine triad, dissolved in dichloromethane are characterized by absorption and emission spectroscopy. The dyads studied are model compounds for the flavin based blue-light photoreceptors phototropin (interaction between FMN and Cys) and BLUF (interaction between FAD and Tyr). The triad was designed to mimic the dye-based functions of blue-light cryptochrome photoreceptors (interaction between MTHF, FAD, and likely Trp). Absorption cross-section spectra, fluorescence quantum distributions, quantum yields, and decay times are determined. The absorption spectra of the dyads and the triad resemble the superposition of the absorption spectra of the constituents (1-methylpyrene, isoalloxazine, and phenylphenothiazine). Photo-excitation of the flavin moiety causes fluorescence quenching by reductive electron transfer in thermodynamic equilibrium with the exited flavin subunit. The charge-separated states recover by charge recombination. Photo-excitation of the pyrene or phenylphenothiazine moiety causes oxidative electron transfer with successive recombination, and additionally Förster-type and Dexter-type energy transfer.