A Ru‐Hbpp‐Based Water‐Oxidation Catalyst Anchored on Rutile TiO2

In support of a split: A water oxidation catalyst based on ruthenium bis‐(2‐pyridyl)pyrazole anchored on rutile TiO2 was prepared. The performance of this new material with regard to its capacity to catalytically oxidize water to molecular oxygen in a heterogeneous phase was evaluated. magnified image Two organic ligands based on bis‐(2‐pyridyl)pyrazole (Hbpp) functionalized with a para‐methylenebenzoic acid (Hbpp‐Ra) or its ester derivative (Hbpp‐Re) were prepared and characterized. The ester‐functionalized ligand was then used to prepare a series of related dinuclear ruthenium complexes of general formula [RuII2(L‐L)(bpp‐Rn)(trpy)2]m+ (L‐L=μ‐Cl, μ‐acetato, or (H2O)2; n=e or a; trpy=2,2′:6′,2′′‐terpyridine; m=2 or 3). The complexes were characterized in solution by 1D and 2D NMR spectroscopy, UV/Vis spectroscopy, and electrochemical techniques. The [RuII2(μ‐Cl)(bpp‐Re)(trpy)2](PF6)2 complex was further characterized in the solid state by X‐ray diffraction. The complexes containing the free carboxylic acid ligand were anchored onto rutile TiO2 and treated with 0.1 M triflic acid solution to generate the homologous water‐oxidation catalysts TiO2‐[RuII2(H2O)2(bpp‐Ra)(trpy)2]2+. This new hybrid material catalytically oxidizes water to molecular oxygen in a heterogeneous manner using CeIV as chemical oxidant. The generation of molecular oxygen is accompanied by the formation of carbon dioxide as well as some leaching of the Ru catalyst.