Heidelberg 2015 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 12: Photochemistry and Catalysis
MO 12.5: Vortrag
Mittwoch, 25. März 2015, 12:15–12:30, PH/HS1
Ultrafast Time-Resolved Spectroscopy of New Reversible Photoswitchable Diarylethene Derivates — •Tiago Buckup1, Sven Mehlhose1, Christopher Sarter2, Andres Jäschke2, Hans-Robert Volpp1, and Marcus Motzkus1 — 1Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg. — 2Institut für Pharmazie und Molekulare Biotechnologie, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany.
Diarylethenes (DE) are an important class of compounds with promising applications due to their photochromatic behavior. Recently, photoswitchable DEs were combined with the structural features and molecular recognition properties of nucleic acids to design new photochromic nucleosides [1]. In this work, we investigate the ultrafast dynamics of the ring-opening photo-reaction of several DE derivates with ultrashort excitation (<20 fs) in transient absorption. We observe a very fast excited state ballistic deactivation of the Franck Condon region towards the conical intersection (CI) within the first 300 fs. The ring-opening reaction takes place within 1.6-5.5 ps, depending on the DE derivate. The branching ratio at the CI can be estimated by the incomplete recovery of the bleach signal of the closed-form absorption between 450-500 nm. The quantum yield for the ring-opening photo-reaction of such DE derivates is significantly enhanced (over 70% efficiencies) by specific thiophene substitutions. A global target analysis (GTA) of transient absorption data further depicts a simple kinetic model starting with a sequential reaction followed by a branching reaction at the CI. [1] Singer, et al, JACS 132 (2010) 8372.