Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 98: Organic-Inorganic Systems V: Adsorption on Metals

O 98.7: Talk

Friday, March 11, 2016, 12:00–12:15, H24

Beyond the hexagon: Non-alternant aromatic molecules on metal surfaces — Benedikt P. Klein, Philipp Müller, Johanna Schepp, Falk Niefind, Malte Zugermeier, Maik Schöniger, Martin Schmid, and •J. Michael Gottfried — Fachbereich Chemie, Philipps-Universität Marburg, Germany

The interaction of conjugated organic hydrocarbons, in particular aromatic species, with metal surfaces has been a major topic in surface science during the past decade. Up to now, the focus has been almost exclusively on alternant hydrocarbons, which are characterized by an even charge distribution and highly delocalized frontier orbitals. In contrast, non-alternant hydrocarbons have uneven charge distributions, which can result in considerable in-plane dipole moments, and more localized frontier orbitals. They also do not obey the Coulson-Rushbrooke pairing theorem and thus have shifted valence levels compared to the isomeric alternant hydrocarbons. In this contribution, we present the first systematic studies of non-alternant aromatic hydrocarbons on the (111) surfaces of Cu, Ag and Au. In particular, we focus on naphthalene as an alternant hydrocarbon and bicyclo[5.3.0]decapentaene (BDP) as its non-alternant counterpart. On the basis of extensive NEXAFS, PES, TPD and STM studies, we show that the non-alternant hydrocarbon interacts much stronger with the metal surfaces, especially in the case of Cu(111), and that the interaction is more localized. The non-alternant species also experiences a considerable out-of-plane deformation, which results from the localization of the frontier orbitals.