Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 16: Organic, Polymeric, and Biomolecular Films I
O 16.9: Vortrag
Montag, 26. März 2007, 16:15–16:30, H42
DFT applied to functionalized Azobenzene: Towards a description of molecular switches on alkanethiol SAMs — •Erik McNellis, Volker Blum, Patrick Rinke, and Karsten Reuter — Fritz-Haber-Institut, Faradayweg 4-6, D-14195, Berlin
Molecules with a reversible and controllable binary property are a research topic of increasing relevance. Azobenzene (C6H5-N2-C6H5) and its derivatives represent one class of such ’molecular switches’, with a known cis-trans isomerization in solution. In surface mounted geometries, ligands may be used to decouple the switch from the solid surface. The ligand may itself be chosen with a particular functionality in mind: e.g., an alkanethiol chain adds self-assembly capability to the molecular switch.
We employ density-functional theory (DFT) and linear response time-dependent DFT to study the effect of such ligands and different non-polar or polar head groups (e.g. CF3, CH3) on the molecular geometry and the resonant excitation energies, discussing the results in the context of self-assembled monolayers (SAMs). Depending on the nature of the linker group (e.g. O, NH, CH2) used to bind the alkane, as well as the employed head group, the excitation energies may be tuned by approximately 0.5 eV. The computed structural properties provide conceptual insights into steric effects and a possible orientational order of the molecular switches.