Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 34: Metal Substrates: Adsorption of Organic/Bio Molecules II

O 34.2: Talk

Tuesday, February 26, 2008, 14:00–14:15, MA 043

Spectroscopic mapping of chirality at the molecular level: PVBA on Cu(111) — •Robin Ohmann, Lucia Vitali, and Klaus Kern — Max-Planck-Institute for Solid State Research, Stuttgart, Germany

Chirality is a fundamental aspect of molecular biology and biochemistry, and is of central importance in pharmaceutics, yet directly imaging chirality of molecules proves to be challenging. Here, we present a combined scanning tunneling microscopy (STM) and spectroscopy (STS) study of 4-[trans-2-(pyrid-4-yl-vinyl)] benzoic acid (PVBA) adsorbed on a Cu(111)-surface. The molecules, deposited in ultra high vacuum (UHV) via molecular beam epitaxy, have been measured at low temperature (6 K). Single PVBA molecules (monomers), which become chiral upon adsorption on the surface, dimers and linear as well as triangular ensembles consisting of more than two molecules are observed. The contribution of different molecular orbitals to the local density of states has been measured for monomers and dimers by acquiring conductance maps. This allows directly visualizing the chirality of the adsorbed molecules. In the case of dimers we found homochiral and heterochiral species, which show respectively point-symmetric and mirror-symmetric spectroscopic features. Furthermore the interaction of monomers and dimers with the surface, as revealed by the scattering of the standing waves, will be discussed.