Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 36: Posters: Bio/organic Molecules on Surfaces, Graphene, Solid/liquid interfaces, Metal Substrates, Electronic Structure Theory
O 36.31: Poster
Dienstag, 1. April 2014, 18:30–22:00, P1
Light-induced ring opening of a submonolayer nitrospiropyran electronically decoupled from a Cu(100) surface — •Fabian Nickel1, Matthias Bernien1, Qingyu Xu1,2, and Wolfgang Kuch1 — 1Freie Universität Berlin, Institut für Experimentalphysik, Arnimallee 14, 14195 Berlin — 2Southeast University, Department of Physics, Nanjing 211189, P. R. China
The electronic properties of spiropyran (SP) molecules are known to change enormously after a ring opening to merocyanine (MC). Current research focuses on the isomerization of molecules in direct contact with a surface. These systems might have a great potential for applications to switch properties by external stimuli such as light. In this work the adsorption of SP on a Cu(100) surface covered by a double layer of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) was studied by near-edge x-ray absorption fine structure (NEXAFS). PTCDA adsorbs planar on the Cu(100) surface and is supposed to reduce the interaction of the overlying molecular layer with the metal substrate. At a temperature of 200 K, the SP molecules are physisorbed in the closed-ring conformation. A ring opening by illumination with UV light could be achieved for this system. A change in the out-of-plane nitrogen x-ray absorption can clearly be assigned by density functional theory to the switching of SP to the zwitterionic MC mesomere. Polarization-dependent spectra of the nitrogen and oxygen K edge show a slight change of the angle dependence due to a possible tilting of the molecule.
This work is supported by the DFG through Sfb 658.