Photoisomerization ability of molecular switches adsorbed on Au(111): Comparison between azobenzene and stilbene derivatives

Felix Leyssner, Sebastian Hagen, László Óvári, Jadranka Dokić, Peter Saalfrank, Maike V. Peters, Stefan Hecht, Tillmann Klamroth, P. Tegeder

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39 Citations (Scopus)

Abstract

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 tetratert- butyl-stilbene (TBS) on Au(111). The results are compared with the azobenzene analogue, tetra-tertbutyl- 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.

Original languageEnglish
Pages (from-to)1231-1239
Number of pages9
JournalJournal of Physical Chemistry C
Volume114
Issue number2
DOIs
Publication statusPublished - Jan 21 2010

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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    Leyssner, F., Hagen, S., Óvári, L., Dokić, J., Saalfrank, P., Peters, M. V., Hecht, S., Klamroth, T., & Tegeder, P. (2010). Photoisomerization ability of molecular switches adsorbed on Au(111): Comparison between azobenzene and stilbene derivatives. Journal of Physical Chemistry C, 114(2), 1231-1239. https://doi.org/10.1021/jp909684x