Coding Solvation Workshop

Accelerated Dynamics Simulations of Supramolecular Ruthenium-Based Water Oxidation Catalysis

Joachim O. Lindner (Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Emil-Fischer-Str. 42, 97074 Würzburg, Germany)
Merle I. S. Röhr (Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Emil-Fischer-Str. 42, 97074 Würzburg, Germany)
Roland Mitric (Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Emil-Fischer-Str. 42, 97074 Würzburg, Germany)

Water oxidation is a key step in the development of new sustainable methods
towards artificial photosynthesis and solar fuels. A promising approach for
efficient water splitting is the design of supramolecular Ru-based catalysts.
[1] Only recently, a macrocyclic system containing three Ru(bda) units (bda =
2,2’-bipyridine-6,6’-dicarboxylate) has been synthesized that is able to
compete with the best catalysts up to date in TOF and TON while mechanistically
following a pathway characterized by the nucleophilic attack of a water
molecule. [2] QM/MM molecular dynamics simulations allowed us to observe the
whole catalytic cycle of this supramolecular catalyst in solution. Furthermore,
by comparison of systems with increas- ing ring sizes we could show that the
high catalytic activity and characteristic absorption bands in the UV/Vis
spectra are due to pronounced hydrogen bonding networks that are formed
preferably in the macrocycle with intermediate size. [3] Cooperative effects
lead to the stabilization of dissociated protons and thus facilitate
proton-coupled electron transfer processes. In order to gain a deeper
understanding of the mechanistic details in these supramolecular systems, we
apply the metadynamics approach to quantitatively identify the rate-determining
steps of the catalytic cycle as well as possible changes in the reaction
pathway affecting the enhanced water oxidation activity of the macrocycle.

[1] V. Kunz, D. Schmidt, M. I. S. Röhr, R. Mitric, F. Würthner, Adv. Energy Mater., doi: 10.1002/aenm.201602939 (2017).
[2] M. Schulze, V. Kunz, P. D. Frischmann, F. Würthner, Nat. Chem. 8, 576–583 (2016).
[3] V. Kunz, J. O. Lindner, M. Schulze, M. I. S. Röhr, D. Schmidt, R. Mitric, F. Würthner, Energy Environ. Sci., submitted.