Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 45: Organic-Inorganic Hybrid Systems and Organic Films

O 45.11: Poster

Tuesday, March 21, 2017, 18:30–20:30, P1A

Topology Dependent Molecule-Substrate Interactions: Azulene vs. Naphthalene in Temperature-Programmed Desorption — •Stefan Renato Kachel, Maik Schöniger, Martin Schmid, and J. Michael Gottfried — Fachbereich Chemie, Philipps-Universität Marburg, Germany

Understanding the interaction of π-conjugated organic molecules with metal surfaces is crucial for the development of modern organic electronic devices. To uncover how the topology of the π-system influences the surface chemical bond, the structural isomers azulene and naphthalene on Ag(111) and Cu(111) were investigated by temperature-programmed desorption. While naphthalene has a benzoid, alternant topology, azulene is a prototypical example for a π-system with a non-alternant topology. On Cu(111), azulene has a much higher desorption temperature (520 K) than naphthalene (340 K) in the limit of low coverage, while the difference is less pronounced on Ag(111). With increasing submonolayer coverage, all systems show substantial peak broadening towards lower temperatures, which is typical for intermolecular repulsion. The effect is most pronounced for azulene/Cu(111), where the monolayer signals spread over almost 300 K. Refined analysis on the basis of heating-rate variation studies provides desorption energies of 165 kJ/mol for azulene and 100 kJ/mol for naphthalene, both on Cu(111). The large energy difference indicates that the topology of the molecular π-system has enormous influence on the molecule-substrate interaction.