Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 69: Poster Wednesday: Organic Molecules on Inorganic Surfaces
O 69.1: Poster
Mittwoch, 3. April 2019, 17:45–20:00, Poster B2
Reactions of Tetrapyrroles with Lead on Metal Surfaces — •Mark Hutter1, Malte Zugermeier1, Guoqing Lyu2, Martin Schmid1, Stefan Renato Kachel1, Nian Lin2, and J. Michael Gottfried1 — 1Fachbereich Chemie, Philipps-Universität Marburg, Germany — 2Department of Physics, The Hong Kong University of Science and Technology, Hongkong, China
Metal complexes of tetrapyrroles such as porphyrins and phthalocyanines play important roles in living organisms and for various technological applications. While most studies focus on transition metal complexes, we report here the interaction of tetrapyrrole monolayers with Pb as a typical main group metal. STM shows that tetrapyridylporphyrin (2HTPyP) on Au(111) reacts with metallic Pb, as evidenced by increased apparent heights in the molecular centers. Corresponding XPS studies with tetraphenylporphyrin (2HTPP) show the presence of Pb(II), indicating the formation of a Pb(II)TPP complex. Interestingly, annealing to 520 K leads to a reduction of the apparent height and the Pb(II) related XPS signal decreases. These findings are consistent with two possible mechanisms. In the first one, Pb(II)TPP is initially formed in a Pb-up geometry, such that the Pb(II) ion is detached from the Au substrate and thus retains its nominal oxidation state. Annealing transforms the complex to Pb-down geometry, in which the Pb(II) center receives electron density from the substrate and is reduced to Pb(0). In the second one, the Pb(II) center is replaced by a substrate Au atom upon annealing. For further clarification, TPD/AES studies were performed.