Place: Kleiner Physik-Hörsaal, Geschwister-Scholl-Platz
Date: 06.11.09, Time: 15:30 h
Chiral-self assembly, tiling, and electronic structure of supported rubrene molecules: A local view
Prof. Wolf-Dieter Schneider
Ecole Polytechnique Fédérale de Lausanne
Surface nanostructuring by molecular self-organisation is a relevant process in the growing field of nanotechnology. Depending on the characteristics of the molecules and on the type of interactions among them and with the substrate, a variety of supramolecular structures have been observed by scanning tunneling microscopy. In the formation of these molecular patterns chiral recognition and tiling play a fundamental role, which is shown in a particularly illustrative example for the organic molecule rubrene on a reconstructed Au(111) surface. We observe the spontaneous chiral resolution of the racemate into disjoint homochiral complex architectures and demonstrate the ability to monitor the evolution of chiral recognition processes on the molecular and supramolecular level. We detect two-dimensional tiling with both nonperiodic and periodic arrangements of slightly distorted supramolecular pentagons, hexagons, and heptagons reflecting the three-dimensional nonplanar flexible structure of the molecule. We are able to probe and to locally modify the intrinsic electronic structure and the conformation of the supported nonplanar molecules. Theoretical modeling reveals that the observed one-dimensional assembly behaviour into meandering pentagon chains is the result of the coexistence of short-range attractive forces with electrostatic repulsive forces between individual pentagons.