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O: Fachverband Oberflächenphysik
O 56: Metal substrates: Adsorption of organic / bio molecules VI
O 56.4: Vortrag
Mittwoch, 24. März 2010, 15:45–16:00, H36
The Role of Functional Groups for the Switching Efficiency of Surface-Adsorbed Molecular Switches — •Erik R. McNellis1 and Karsten Reuter1,2 — 1Fritz-Haber-Institut Berlin (Germany) — 2Technische Universität München (Germany)
Azobenzene (C6H5-N=N-C6H5) adsorbed at coinage metal surfaces has transformed into an increasingly studied prototype system for a surface-adsorbed molecular switch. With photo-induced switching between the cis and trans configuration suppressed for bare azobenzene, controlled decoupling from the surface through bulky functional groups appears as a promising strategy. In particular, tetra-tert-butyl azobenzene (TBA), in which groups of three butyl (CH3) groups are added to both meta positions of each phenyl ring, can be efficiently switched at Au(111), albeit not at Ag(111). In order to shed more light on the role of the functional groups and surface electronic structure for the different switching efficiency we perform density-functional theory calculations, accounting for van der Waals interactions on the level of semi-empirical dispersion correction schemes. The thereby obtained structural and vibrational properties of both bare azobenzene and TBA at Ag(111) and Au(111) compare favorably with existing experimental data. In the analysis of the electronic structure we focus on the hybridization of the molecular frontier orbitals with the substrate states, and discuss this in the context of previously published hypotheses concerning the switching mechanism of surface-adsorbed TBA.