Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 75: Organic/bio Molecules on Metal Surfaces VI
O 75.4: Vortrag
Donnerstag, 14. März 2013, 16:45–17:00, H38
Coverage-dependent metalation of tetraphenylporphyrin with Cu(111) — •Michael Röckert, Jie Xiao, Stefanie Ditze, Michael Stark, Mathias Grabau, Hubertus Marbach, Hans-Peter Steinrück, and Ole Lytken — LS für PC II, Universität Erlangen-Nürnberg, Egerlandstraße 3, D-91058 Erlangen
The coverage-dependent metalation of tetraphenylporphyrin (2HTPP) with Cu atoms from a Cu(111) substrate has been investigated by X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM) from submonolayer to multilayer coverages. At coverages below 0.17 molecules/nm2 the rate of metalation is modest and follows a first order behaviour. However, as the coverage is increased beyond 0.35 molecules/nm2 a strong increase in the rate of metalation is observed, and the rate no longer follows a simple first order behaviour. This behaviour is accompanied by the appearance of a checkerboard structure at coverages above 0.35 molecules/nm2 as found by STM. Temperature-dependent rates of metalation have been measured for both high (>0.35 molecules/nm2) and low (<0.35 molecules/nm2) coverage, and, based on Arrhenius analyses, prefactors and activation energies for the two reaction channels have been extracted. It was found that the metalation reaction for the high-coverage checkerboard structure had a significantly lower activation energy compared with coverages below 0.17 molecules/nm2. The reason for the increased reactivity could be easier access of copper adatoms to the slightly elevated porphyrin molecules in the checkerboard structure.
Supported by the DFG through SFB 583.