Hannover 2020 – scientific programme

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MO: Fachverband Molekülphysik

MO 15: MO Poster 3

MO 15.1: Poster

Wednesday, March 11, 2020, 17:00–19:00, Empore Lichthof

Photochemical formation and photophysical properties of photocatalyst radicals — •Sebastian Bergwinkl and Bernhard Dick — Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Germany

Recently, organic radicals have been proposed as photocatalysts. Although such radicals are sensitive to oxygen, their electronic excitation leads to potentially strong reducing species that may be used in photoredox catalysis. When these radicals are themselves produced by a photochemical reaction, the catalytic process uses the energy of two photons [1]. Results of time-resolved spectroscopic measurements will be presented that follow the kinetics of the photochemical formation of the rhodamine radical.

Transient absorption spectra obtained with a streak camera show that a single photon absorbed by a rhodamine molecule produces two radicals of this species. One is formed by direct photoinduced electron transfer, the second by a dark reaction on a microsecond time scale, allowing for a theoretical upper limit of the quantum yield of 2. The rhodamine radical is stable for many minutes, but decomposes quickly upon excitation with a second photon.

[1] I. Gosh, T. Gosh, J. I. Bardagi, B. König, Science 2014, 346, 725–728.