Ab Initio Molecular Dynamics Study of Water Oxidation Reaction Pathways in Mono-Ru Catalysts

• Published in: Chemphyschem 2012-01, Vol.13 (1), p.140-146
• Main Authors: Vallés-Pardo, José Luis, Guijt, Marieke C., Iannuzzi, Marcella, Joya, Khurram S., de Groot, Huub J. M., Buda, Francesco
• Format: Article
• Language: English
• Subjects: ab initio calculations; Catalysis; Chemistry; Coordination Complexes - chemistry; density functional calculations; Exact sciences and technology; General and physical chemistry; Ions - chemistry; molecular dynamics; Molecular Dynamics Simulation; Oxidation-Reduction; Ruthenium - chemistry; ruthenium catalysts; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Water - chemistry; water splitting
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201100546

Ab initio molecular dynamics simulations with an adaptive biasing potential are carried out to study the reaction path in mononuclear Ru catalysts for water oxidation of the type [(Ar)Ru(X)(bpy)]+ with different aromatic ligands (Ar). The critical step of the OO bond formation in the catalytic cycle starting from the [(Ar)Ru(O)(bpy)]2+ intermediate is analyzed in detail. It is shown that an explicit inclusion of the solvent environment is essential for a realistic description of the reaction path. Clear evidence is presented for a concerted reaction in which the OO bond formation is quickly followed by a proton transfer leading to a RuOOH intermediate and a hydronium ion. An alternative path in which the approaching water first coordinates to the metal centre is also investigated, and it is found to induce a structural instability of the catalyst with the breaking of the aromatic ligand coordination bond. A molecule divided: Ab initio molecular dynamics simulations are used to study the reaction path in mononuclear Ru catalysts for water oxidation. The Ru‐hydroperoxo intermediate and the hydronium ion formed during the ab initio molecular dynamics simulation in water are shown in the picture. This is a crucial step in the catalytic cycle of the water splitting reaction.