SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 6: Poster Session I: Organic molecules on inorganic substrates: Adsorption and growth I
O 6.6: Poster
Montag, 1. März 2021, 10:30–12:30, P
Adsorption energies of metalloporphyrins on MgO(100) — •Alexander Wolfram1, Quratulain Tariq1, Cynthia Fernandez2, Bernd Meyer3, Daniel Wechsler1, Matthias Franke1, Hans-Peter Steinrück1, Federico Williams2, and Ole Lytken1 — 1Lehrstuhl für Physikalische Chemie 2, Friedrich-Alexander Universität Errlangen-Nürnberg, GER — 2Departamento de Química Inorgánica, Analítica y Química Física, Universidad de Buenos Aires, Ciudad Universitaria, ARG — 3ICMM/CCC, Friedrich-Alexander-Universität Erlangen-Nürnberg, GER
Adsorption energies of large organic molecules on surfaces are often not well known. Experimentally, the large molecules are prone to decomposition before desorption, often ruling out desorption-based techniques. Theoretically, van der Waals interactions, which dominate the interactions between the molecules and the surface, are still challenging. However, for tetraphenylporphyrin adsorbed on MgO(100) desorption of the monolayer is possible, and, using simple Redhead analysis, we have extracted the desorption energies of cobalt, zinc, and magnesium tetraphenylporphyrin. Redhead analysis requires the prefactor for desorption to be known, and we have estimated this prefactor by a combination of transition-state theory and experimentally-derived prefactors from multilayer desorption. The resulting desorption energies are in good agreement with density functional theory calculations. Somewhat unexpectedly, CoTPP exhibits the lowest desorption energy and MgTPP the highest. We suggest the different oxophilicities of the metal centers to be the reason for the trend in adsorption energy.