Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 37: Metal substrates: Adsorption of organic / bio molecules V
O 37.7: Vortrag
Mittwoch, 25. März 2009, 16:30–16:45, SCH A118
Structure and excitonic coupling in self-assembled monolayers of azobenzene-alkanethiols on gold — •Cornelius Gahl1, Roland Schmidt1,2, Daniel Brete1,2, Erik McNellis3, Wolfgang Freyer1, Robert Carley1, Karsten Reuter3, and Martin Weinelt1,2 — 1Max-Born-Institut, Max-Born-Str. 2a, 12489 Berlin, Germany — 2Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — 3Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany
Self-assembled monolayers of azobenzene-functionalized alkanethiols have been investigated with respect to their geometric structure and optical properties by UV/Visible and near-edge X-ray absorption fine structure spectroscopy in combination with density-functional theory. By attaching a trifluoro-methyl endgroup to the chromophore both the molecular tilt and twist angle of the azobenzene moiety are determined. Based on this detailed structure analysis the energetic shifts observed in optical reflection spectroscopy can be qualitatively described within an extended dipole model. This substantiates sizeable excitonic coupling among the chromophores and elucidates why trans to cis isomerization of the azobenzene photoswitch is strongly suppressed in densely-packed self-assembled monolayers.