Rostock 2019 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 22: Posters 3: Cluster, Strong Field Physics, and Experimental Techniques

MO 22.5: Poster

Donnerstag, 14. März 2019, 16:15–18:15, S Foyer LLM

Water deprotonation on free calcium-manganese-oxide clusters: Gas Phase Model Systems for the Catalytically Active Center of Photosystem II — •Sandra M. Lang, Irene Fleischer, Silvia Mauthe, Nina Zimmermann, and Thorsten M. Bernhardt — Institute of Surface Chemistry and Catalysis, Ulm University, Albert-Einstein-Allee 47, 89069 Ulm, Germany

The catalytic oxidation of water in plants takes place at an inorganic Mn₄CaO₅ cluster located in photosystem II. To aid the design of new artificial water oxidation catalysts we embark on a novel hierarchical modeling strategy, starting with small clusters and increasing the model system’s complexity in a staged, controlled manner.

In the first steps we studied the reactivity of isolated manganese oxide cluster ions, Mn_xO_y⁺, of different size and composition with D₂¹⁶O and H₂¹⁸O. Gas-phase ion trap experiments and infrared multiple-photon dissociation (IR-MPD) spectroscopy in conjunction with first-principles calculations, revealed the facile water deprotonation and the exchange of the oxygen atoms of the cluster with water oxygen atoms.

In a further step we investigated binary calcium manganese oxide clusters and found that the number of Ca atom is crucial to the water oxidation capabilities of the small Ca_4−xMn_xO₄⁺ and Ca_5−xMn_xO₅⁺ clusters. Finally, we started modeling the ligand environment of the manganese-clusters cluster by small acids. First experiments identified propionic acid as the most promising candidate since the smaller acids, formic and acetic acid, easily decompose in the presence of Mn_xO_y⁺.