Regensburg 2007 – scientific programme

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O: Fachverband Oberflächenphysik

O 16: Organic, Polymeric, and Biomolecular Films I

O 16.4: Talk

Monday, March 26, 2007, 15:00–15:15, H42

Polymorphism of Porphyrin Molecules on Ag(111): and how to weave a rigid monolayer — •Hubertus Marbach, Florian Buchner, Karmen Comanici, and Hans-Peter Steinrück — Universität Erlangen-Nürnberg, Lehrstuhl für Physikalische Chemie II, Egerlandstraße 3, D-91058 Erlangen, Germany

Organic molecules play a prominent role for the development of new materials and molecular devices. An important group of such molecules are porphyrins. Their versatility and distinct chemical and electronic properties make them promising candidates for tailored catalytic processes and as building blocks for nanoscaled electronic devices. In the present paper we focus on studying the molecular arrangements of Cobalt-5,10,15,20-Tetraphenylporphyrin (CoTPP) and Cobalt-5,10,15,20-Tetrakis-(3,5-di-tert-butyl)-phenyl*porphyrin (CoTTBPP) on an Ag(111) surface by means of scanning tunneling microscopy (STM) in ultra high vacuum. In the monolayer regime, ordered domains were found for both investigated porphyrins. Whereas the smaller CoTPP exhibits only one molecular arrangement (square order), for the larger CoTTBPP four clearly distinguishable phases (two hexagonal, one square and one herringbone) were observed. Submolecularly resolved STM images reveal that the different molecular arrangments go together with different conformations of the individual molecules. The herringbone structure was solely observed after a thermal treatment and consists of interwoven molecules, which makes this phase especially rigid.

This work has been funded by Sonderforschungsbereich 583