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Schlagwörter:
tert-butyl-azobenzene; self-assembled monolayers; electronic-structure; thermal-activation; para-nitroaniline; isomerization; light; spectroscopy; spectra; photochemistry
Zusammenfassung:
High resolution electron energy loss spectroscopy is employed to analyze the adsorption geometry and the photoisomerization ability of the molecular switch carboxy-benzylideneaniline (CBA) adsorbed on Au(111). CBA adopts on the Au(111) surface a planar (trans) configuration in the first monolayer (ML) as well as for higher coverages (up to 6 ML), contrary to the geometry in solution, which is strongly non-planar. Illumination with UV light of CBA in direct contact with the Au(111) surface (≤ 1 ML) caused no changes in the vibrational structure, whereas at higher coverages ( > 1 ML) pronounced modifications of vibrational features are observed, which we assign to a trans → cis isomerization. Thermal activation induced the back reaction to trans-CBA. We propose that the photoisomerization is driven by a direct (intramolecular) electronic excitation of the adsorbed CBA molecules in the second ML (and above) analogous to CBA in the liquid phase.
