Enhanced Ab Initio Molecular Dynamics Exploration Unveils the Complex Role of Different Intramolecular Bases on the Water Nucleophilic Attack Mechanism

Abstract

Rational design of water oxidation catalysts (WOCs) is a valuable complement to the traditional empirically driven approach used to improve the catalytic performance of existing catalysts. The validity of those predictions depends on the applied simulation protocol and its capability to account for all relevant aspects of the catalytic system. Commonly used approaches often only include an approximative treatment of solute-solvent interactions and neglect dynamic effects occurring at ambient temperature. In order to go beyond those limitations, we rely on a density functional theory-based molecular dynamics (DFT-MD) simulation protocol, which shows that the inclusion of those effects is essential in order to understand the O-O bond formation process in various facets. In this work, we focus on the effects of a modification to the Py5 ligand framework of a Ru-based WOC. Previously, it was suggested that increasing the basicity of the pyridyl subunit results in a lower activation barrier for the O-O bond formation [Dalton Trans. 2018, 47, 10780-10490]. We take advantage of the metadynamics method to efficiently explore the O-O bond formation event using DFT-MD. This allows us not only to investigate in detail the beneficial effect an increased basicity has on the O-O bond formation but also to rationalize its origin and complexity that is in part found in the structure of the first solvation shell of the catalyst.