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O: Fachverband Oberflächenphysik
O 35: Poster Session II (Polymeric biomolecular films; Nanostructures; Electronic structure; Spin-orbit interaction; Phase transitions; Surface chemical reactions; Heterogeneous catalysis; Particles and clusters; Surface magnetism; Electron and spin dynamics; Surface dynamics; Methods; Electronic structure theory; Functional molecules)
O 35.141: Poster
Dienstag, 27. März 2012, 18:15–21:45, Poster B
Reversible switching process of spiropyran on Au(111) — F. Lorbeer1, •P. Stoll1, I. Fernandez Torrente1, T. R. Umbach1, C. Maity2, S. Hecht2, J.I. Pascual1, and K.J. Franke1 — 1Institut für Experimentalphysik, Freie Universität Berlin, Berlin — 2Department of Chemistry, Humboldt-Universität zu Berlin
The isomerisation process of molecules adsorbed on a metal surface can be very different from the one in solution or gas phase. The prototypical light induced ring-opening reaction of spiropyran (SP) to its isomer merocyonine (MC) and the thermally induced ring-closing backreaction in gas phase is not easily reproduced on the surface due to the electronic coupling of molecular orbitals with the substrate states. We study 5',6,8 Tri-tertbutylindolinospirobenzopyran on Au(111) with low temperature scanning tunneling microscopy and spectroscopy. The molecule is functionalised with the three tertbutyl groups to reduce the interaction with the substrate and enable reversible switching. An ordered structure is obtained by mixing SP with thermally isomerised MC. In this ordered structure we can excite a ring-opening reaction of SP by electric field and illumination with 445nm laser light. This change is visible as an upward pointing tertbutyl group and is completely reversible by individually adressing the molecule with a voltage pulse. A complete unfolding into the MC form however does not take place due to steric hindrance in the ordered structure.