Synthesis, characterization, and reactivity of dyad ruthenium-based molecules for light-driven oxidation catalysis

Dyad molecules containing the 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) ligand with general formula [(tpy)Ru(μ-tppz)Ru(X)(L-L)]ⁿ⁺ (X=Cl, CF₃COO, or H₂O; L-L=2,2′-bipyridine (bpy) or 3,5-bis(2-pyridyl)pyrazole (Hbpp); tpy=2,2′:6′,2"-terpyridine) have been prepared, purified, and isolated. The complexes have been characterized by analytical and spectroscopic techniques and by X-ray diffraction analysis for two of them. Additionally, full electrochemical characterization based on cyclic voltammetry, differential pulse voltammetry, and square wave voltammetry has been also performed. The pH dependence of the redox couples for the aqua complexes have also been studied and their corresponding Pourbaix diagrams drawn. Furthermore, their capacity to catalytically oxidize organic substrates, such as alcohols, alkenes, and sulfides, has been carried out chemically, electrochemically, and photochemically. Finally, their capacity to behave as water oxidation catalysts has also been tested.