title: A comprehensive picture of the ultrafast excited-state dynamics of retinal.
abstract: All-trans retinal is the chromophore of microbial rhodopsins initiating energy conversion and cellular signalling by subpicosecond photoinduced switching. Here, we provide detailed UV-Vis transient absorption experiments to disentangle the complex photochemistry of this polyene, which is governed by its terminal aldehyde group. After photoexcitation to the S2((1)Bu(+)) state, the system exhibits polarity-dependent branching, populating separate S1((1)Ag(-)) and intramolecular charge transfer (ICT) species. In all solvents, population of a singlet nπ* state from S1 is observed which represents the precursor of the T1 triplet state. While triplet formation dominates in nonpolar solvents (67% quantum yield), it is dramatically reduced in polar solvents (4%). The channel closes completely upon replacing the aldehyde by a carboxyl group, due to an energetic up-shift of (1)nπ*. In that case, internal conversion via the ICT species becomes the main pathway, with preferential formation of the initially excited isomer.
authors.affiliation: Universität Siegen, Physikalische Chemie, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany. oum@chemie.uni-siegen.de lenzer@chemie.uni-siegen.de.
authors.forename: Oliver
authors.initials: O
authors.lastname: Flender
authors.affiliation: Universität Siegen, Physikalische Chemie, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany. oum@chemie.uni-siegen.de lenzer@chemie.uni-siegen.de.
authors.forename: Mirko
authors.initials: M
authors.lastname: Scholz
authors.affiliation: Universität Siegen, Physikalische Chemie, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany. oum@chemie.uni-siegen.de lenzer@chemie.uni-siegen.de.
authors.forename: Jonas
authors.initials: J
authors.lastname: Hölzer
authors.affiliation: Universität Siegen, Physikalische Chemie, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany. oum@chemie.uni-siegen.de lenzer@chemie.uni-siegen.de.
authors.forename: Kawon
authors.initials: K
authors.lastname: Oum
authors.affiliation: Universität Siegen, Physikalische Chemie, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany. oum@chemie.uni-siegen.de lenzer@chemie.uni-siegen.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Lenzer