Hannover 2013 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 21: Femtosecond Spectroscopy V
MO 21.4: Vortrag
Donnerstag, 21. März 2013, 11:45–12:00, F 102
Ultrafast reversible switching dynamics and solvation shell rearrangements of a photo-switchable catalyst tracked from femto to nanoseconds. — •Manuel Pescher1, Luuk van Wilderen1, Susanne Gruetzner2, Stefan Hecht2, and Jens Bredenbeck1 — 1Johann Wolfgang Goethe-Universität, Institut für Biophysik, Frankfurt am Main — 2Humboldt-Universität zu Berlin, Institut für Chemie, Berlin
Photoswitchable catalysts offer means for ultrafast temporal and microscopic spatial control of chemical processes. Here we characterize the behaviour of an azobenzene-based ultrafast photo-switchable catalyst ("Azokat") in an environment of substrate molecules potentially forming H-bonds to the catalytically active site. After optical activation of the catalyst (developed by Stoll et al. [1]) by a 700 fs laser pulse in the visible, the reversible isomerisation of Azokat to its on/off states can be tracked by infrared probe pulses spectrally spanning 200/cm. We measure characteristic eigenvibrations of the system in a regime from 1500/cm up to 3700/cm. This approach resolves the isomerisation and concomitant state-selective binding of hydrogen bond partners and their dynamics, leading to a kinetic model from the femtosecond to nanosecond regime: We observe ultrafast isomerisation of Azokat, leading to chemical activity on a sub-picosecond time scale, subsequent breaking and formation of hydrogen bonds between substrate molecules and the catalyst and finally exchange between species of free and clustered substrate molecules forming hydrogen bonds with each other. [1] Stoll et al, JACS, 131(1):357-67, January 2009.