Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 64: Metal Substrates: Adsorption of Organic/Bio Molecules IV

O 64.3: Talk

Thursday, February 28, 2008, 11:45–12:00, HE 101

Ordering Aspects of Porphyrin Derivates on Ag(111) — •Hubertus Marbach, Florian Buchner, Karmen Comanici, and Hans-Peter Steinrück — Universität Erlangen-Nürnberg, Lehrstuhl für Physikalische Chemie II, D-91058 Erlangen

Porphyrins appear to be ideal candidates to generate functional molecular devices, due to their self assembly properties and their versatile functionality. In the present contribution, we focus on general aspects of ordered phases of different porphyrin derivates in the monolayer regime on Ag(111) investigated by STM. Tetraphenylporphyrins (TPP) always appear to arrange themselves in a square configuration, with a lattice constant of 1.4 nm at RT, independent of the central metal ion. Micrographs with submolecular resolution reveal the details of the molecular arrangement and allow to identify a "T-type" intermolecular interaction in between the phenyl substituents as the main reason for the observed ordering. Interestingly, the TPP molecules tend to rearrange upon exposure to large doses of small molecules (e.g., NO), which is interpreted as due to coadsorption of the dosed molecules. In contrast to TPP, the more bulky Tetrakis-(3,5-di-tert-butyl)-phenyl porphyrins (TTBPP) exhibit different coexisting phases. An specific route to prepare a monolayer, namley the thermal desorption of exess multilayers, leads to an extremley stable CoTTBPP layer, due to a highly interwoven structure. The role of intermolecular and intramolecular interactions and adsorbate/substrate interactions in respect to the observed phases and 2D-chirality aspects will be dicussed. This work has been funded by Sonderforschungsbereich 583.