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          Institute: Fritz-Haber-Institut     Collection: Physical Chemistry     Display Documents

ID: 456335.0, Fritz-Haber-Institut / Physical Chemistry
Photoisomerization Ability of Molecular Switches Adsorbed on Au(111): Comparison between Azobenzene and Stilbene Derivatives
Authors:Leyssner, Felix; Hagen, Sebastian; Ovári, László; Dokic, Jadranka; Saalfrank, Peter; Peters, Maike V.; Hecht, Stefan; Klamroth, Tillmann; Tegeder, Petra
Date of Publication (YYYY-MM-DD):2010
Title of Journal:Journal of Physical Chemistry C
Journal Abbrev.:J. Phys.: Condens. Matter
Issue / Number:2
Start Page:1231
End Page:1239
Copyright:© 2009 American Chemical Society
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:High resolution electron energy loss spectroscopy and two-photon photoemission was employed to derive the adsorption geometry, electronic structure, and the photoisomerization ability of the molecular switch tetra-tert-butyl-stilbene (TBS) on Au(111). The results are compared with the azobenzene analogue, tetra-tert-butyl-azobenzene (TBA), adsorbed on Au(111). TBS was found to adsorb on Au(111) in a planar (trans) configuration similar to TBA. The energetic positions of several TBS-induced electronic states were determined, and in comparison to TBA, the higher occupied molecular states (e.g., the highest occupied molecular orbital, HOMO) are located at similar energetic positions. While surface-bound TBA can be switched with light between its trans and cis configurations, in TBS this switching ability is lost. In TBA on Au(111), the trans → cis isomerization is driven by a substrate-mediated charge transfer process, whereby photogenerated hot holes in the Au d band lead to transient positive ion formation (transfer of the holes to the TBA HOMO level). Even though the energetic positions of the HOMOs in TBA and TBS are almost identical and thus a charge transfer should be feasible, this reaction pathway is obviously not efficient to induce the trans → cis isomerization in TBS on Au(111). Quantum chemical calculations of the potential energy surfaces for the free molecules support this conclusion. They show that cation formation facilitates the isomerization for TBA much more pronounced than for TBS due to the larger gradients at the Franck−Condon point and the much smaller barriers on the potential energy surface in the case of the TBA.
External Publication Status:published
Document Type:Article
Communicated by:Martin Wolf
Affiliations:Fritz-Haber-Institut/Physical Chemistry
External Affiliations:Leyssner F, Ovári L, Tegeder P*, Freie Univ, Dept Phys, Arnimallee 14, D-14195 Berlin, Germany; Dokic J, Saalfrank P, Klamroth T, Univ Potsdam, Theor Phys, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam-Golm, Germany; Peters M.V., Hecht S, Humboldt Univ, Dept Chem, Brook-Taylor-Str. 2, D-12489 Berlin, Germany; Ovári L, Current address: Chem Res Center of HAS, Reaction Kinetics Res Lab, Szeged, Hungary
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