Berlin 2005 – scientific programme

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O: Oberflächenphysik

O 10: Adsorption an Oberfl
ächen I

O 10.3: Talk

Friday, March 4, 2005, 16:15–16:30, TU EB301

Coulombic amino-group–metal bonding: Adsorption of adenine on Cu(110) — •Martin Preuss, Wolf Gero Schmidt, and Friedhelm Bechstedt — Institut für Festkörpertheorie und -optik, Max-Wien-Platz 1, 07743 Jena

The knowledge of the interaction between biologically active molecules such as proteins or nucleic acid and solid surfaces is relevant to the preparation of biocompatible materials and biosensors. The adsorption of small organic molecules, in particular amino acids or nucleic acid bases, on metal surfaces thereby serves as a model case for the understanding of more complex systems as well as reactions between organic molecules. The bonding of molecular amino groups to metal surfaces is of particular interest and has given rise to a number of interpretations. Here we analyze the adsorption of adenine on Cu(110) using first principles calculations. A directional bonding between the amino-group nitrogens and copper surface atoms is found to emerge that cannot simply be explained by covalent or ionic contributions. Instead we propose the established bond to be a result of mutual polarization of the amino-group N lone pair of electrons and the metal substrate. To rationalize this notion we decompose the Coulombic interaction energy due to the charge transfer into monopole and dipole terms.