title: Photochemical Z-->E isomerization of a hemithioindigo/hemistilbene omega-amino acid.
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.
authors.affiliation: Lehrstuhl für BioMolekulare Optik, Department für Physik, Ludwig-Maximilians-Universität, Oettingenstr. 67, 80538 München, Germany.
authors.forename: Thorben
authors.initials: T
authors.lastname: Cordes
authors.forename: Björn
authors.initials: B
authors.lastname: Heinz
authors.forename: Nadja
authors.initials: N
authors.lastname: Regner
authors.forename: Christian
authors.initials: C
authors.lastname: Hoppmann
authors.forename: Tobias E
authors.initials: TE
authors.lastname: Schrader
authors.forename: Wolfram
authors.initials: W
authors.lastname: Summerer
authors.forename: Karola
authors.initials: K
authors.lastname: Rück-Braun
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Zinth
mesh_terms: D000596:Amino Acids / Q000737:chemistry / Q000528:radiation effects*; D008956:Models, Chemical; D010777:Photochemistry; D013057:Spectrum Analysis; D013237:Stereoisomerism; D013876:Thiophenes / Q000737:chemistry*
chemical_list: C523916:2-(4-(aminomethyl)benzylidene)-3-oxo-2H-thiophene-7-carboxylic acid; D000596:Amino Acids; D013876:Thiophenes