Photochemical Z-->E isomerization of a hemithioindigo/hemistilbene omega-amino acid. |
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Authors: | Thorben Cordes Björn Heinz Nadja Regner Christian Hoppmann Tobias E Schrader Wolfram Summerer Karola Rück‐Braun Prof Dr Wolfgang Zinth Prof Dr |
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Institution: | 1. Lehrstuhl für BioMolekulare Optik, Department für Physik, Ludwig‐Maximilians‐Universit?t, Oettingenstr. 67, 80538 München, Germany, Fax: (+49)?89‐2180‐9202;2. Munich Center for Integrated Protein Science CIPSM(Germany);3. Technische Universit?t Berlin, Institut für Chemie, Stra?e des 17. Juni 135, 10623 Berlin, Germany |
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Abstract: | The molecule HTI, which combines hemithioindigo and hemistilbene molecular parts, allows reversible switching between two isomeric states. Photochromic behaviour of the HTI molecule is observed by irradiation with UV/Vis light. The photochemical reaction, a Z/E isomerization around the central double bond connecting the two molecular parts, is investigated by transient absorption and emission spectroscopy. For a special HTI molecule, namely, an omega-amino acid, the Z-->E isomerization process occurs on a timescale of 30 ps. In the course of the reaction fast processes on the 1-10 ps timescale are observed which point to motions of the molecule on the potential-energy surface of the excited state. The combination of transient absorption experiments in the visible spectral range with time-resolved fluorescence and infrared measurements reveal a photochemical pathway with three intermediate states. Together with a theoretical modelling procedure the experiments point to a sequential reaction scheme and give indications of the nature of the involved intermediates. |
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Keywords: | isomerization photochemistry photochromism time‐resolved spectroscopy ultrafast spectroscopy |
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