Regensburg 2013 – scientific programme

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O: Fachverband Oberflächenphysik

O 75: Organic/bio Molecules on Metal Surfaces VI

O 75.1: Talk

Thursday, March 14, 2013, 16:00–16:15, H38

Bonding and chemical transformations of free-base porphyrin species on Ag(111) — •Alissa Wiengarten, Knud Seufert, Willi Auwärter, David Écija, Sushobhan Joshi, and Johannes V. Barth — Physik Department E20, Technische Universität München, D-85748 Garching, Germany

Porphyrins play a key role in many biological processes and are promising building blocks for technical applications. Depending on their substitution and the variation of the metal-center incorporated into the macrocycle, the functionality of these molecules can be tuned. A starting point for a systematic investigation of this class of molecules is the fundamental building block for all porphyrin derivatives, the free-base porphine, forming the macrocycle. In this work we study temperature-induced covalent coupling of free-base porphines on the Ag(111) surface via low temperature scanning tunneling microscopy (LT-STM) in ultra high vacuum (UHV). We find that porphines can dehydrogenate and form direct C-C bonds on a hot surface. With increasing sample temperature the number of covalently bound oligomers increases. A further step focuses on the investigation of tetraphenyl-porphyrins on Ag(111), where the molecule shows a so called saddle-shape deformation. Similar to the porphine case annealing induces dehydrogenation reactions resulting in the formation of different porphyrin-derivatives lying flat on the surface.