Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 98: Organic Molecules on Inorganic Substrates VII

O 98.2: Vortrag

Freitag, 5. April 2019, 10:45–11:00, H17

Physical decoupling of tetrapyrrolic metal-organic complexes on metal surfaces via self-assembled monolayers — Peter S. Deimel, Peter Feulner, Johannes V. Barth, and •Francesco Allegretti — Physik Department E20, Technische Universität München, Deutschland

Tuning the electronic properties of metal-organic complexes such as metalloporphyrins (MPs) and metallophthalocyanines (MPcs) holds promise for their targeted application in, e.g., photocatalysis and molecular sensors. In such cases, the complexes will be ``immobilized'' on solid supports, and for such reason numerous studies have focused on their adsorption on model metal surfaces in vacuo. As MPs and MPcs typically adsorb with their tetrapyrrole macrocycle almost parallel to the metal surface, the interaction between the latter and the central metal ion can decisively alter the chemical and functional properties of the adsorbed complex and even quench its reactivity. Herein we explore a simple strategy to decouple, both spatially and electronically, two prototypical Fe-phthalocyanine and Ru-porphyrin monolayers from a Ag(111) surface, by preventing direct physical contact with the Ag support via insertion of a self-assembled monolayer (SAM) of fluorothiophenol. By combining photoelectron spectroscopy, temperature programmed desorption and low-energy electron diffraction, we show that at low temperatures the thiolate SAM indeed acts as molecular spacer layer. However, already below 300 K, the decoupling breaks down, resulting in an inverted layer stacking followed by complete removal of the SAM molecules at elevated temperatures.