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O: Fachverband Oberflächenphysik

O 22: Organic-Inorganic Hybrid Systems and Organic Films III

O 22.4: Vortrag

Montag, 20. März 2017, 17:45–18:00, WIL A317

Molecular Topology and Surface Chemical Bond: Alternant vs. Non-Alternant Aromatic Molecules — •Benedikt P. Klein¹, Nadine van der Heijden², Claudio K. Krug¹, Maik Schöniger¹, Phil Rosenow¹, Martin Schmid¹, Ralf Tonner¹, Ingmar Swart², and J. Michael Gottfried¹ — ¹Fachbereich Chemie, Philipps-Universität Marburg, Germany — ²Debye Institute for Nanomaterial Science, Utrecht University, The Netherlands

The interaction of conjugated organic molecules, in particular aromatic species, with metal surfaces has been a major topic in surface science. So far, the focus has almost exclusively been on molecules with alternant topologies such as pentacene. These molecules have a uniform charge distribution and highly delocalized frontier orbitals. In contrast, non-alternant topologies cause non-uniform charge distributions, and more localized frontier orbitals. We present the first systematic studies of naphthalene and its non-alternant counterpart azulene on the (111) surfaces of Cu and Ag. On the basis of extensive PES, NEXAFS, TPD, nc-AFM and STM studies, we show that the non-alternant topology results in much stronger interaction with metal surfaces, especially in the case of Cu(111), and that the interaction is more localized. Periodic DFT calculations provide insight into the surface chemical bond and charge redistribution between surface and molecule. A major part of the localized interaction is the donation of electron density in the molecular LUMO. This leads to a considerable in-plane and out-of-plane deformation of the adsorbed non-alternant species.