Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 37: Metal substrates: Adsorption of organic / bio molecules V

O 37.1: Vortrag

Mittwoch, 25. März 2009, 15:00–15:15, SCH A118

A new approach to probe molecular orientation in aromatic self-assembled monolayers — Nirmalya Ballav¹, Björn Schüpbach², Ole Dethloff², Peter Feulner³, Andreas Terfort^2,4, and •Michael Zharnikov¹ — ¹Angewandte Physikalische Chemie, Universität Heidelberg, 69120 Heidelberg, Germany — ²Department Chemie, Philipps-Universität Marburg, 35032 Marburg, Germany — ³Physikdepartment E20, Technische Universität München, 85747 Garching, Germany — ⁴Institut für Anorganische u. Analytische Chemie, Goethe-Universität Frankfurt, 60438 Frankfurt, Germany

The emergence of new technologies has triggered significant interest in aromatic self-assembled monolayers (SAMs). Applications of these systems rely on a precise knowledge of their structure, which can be in particular studied by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. There are, however, principal constraints, which makes it impossible to get complete information on the molecular orientation in aromatic SAMs on the basis of the NEXAFS data. To avoid these constraints, we apply a new approach, attaching to the oligophenyl backbone a specific group (nitrile) with two mutually perpendicular molecular orbitals, which, due to the hybridization with the orbitals of the phenyl rings comprising the backbone, are oriented either perpendicular or parallel to the backbone plane. Analysis of the data suggests that that aromatic molecules in the respective SAMs on Au(111) substrate are not only tilted, but also noticeably twisted, with the exact twist angle depending on molecular architecture.