title: A Ru-Hbpp-based water-oxidation catalyst anchored on rutile TiO2.
abstract: Two organic ligands based on bis-(2-pyridyl)pyrazole (Hbpp) functionalized with a para-methylenebenzoic acid (Hbpp-R(a)) or its ester derivative (Hbpp-R(e)) were prepared and characterized. The ester-functionalized ligand was then used to prepare a series of related dinuclear ruthenium complexes of general formula [Ru(II)2(L-L)(bpp-R(n))(trpy)2](m+) (L-L=mu-Cl, mu-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 [Ru(II)2(mu-Cl)(bpp-R(e))(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 TiO(2)-[Ru(II) (2)(H2O)(2)(bpp-R(a))(trpy)2]2+. This new hybrid material catalytically oxidizes water to molecular oxygen in a heterogeneous manner using Ce(IV) 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.
authors.affiliation: Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193 Barcelona, Spain.
authors.forename: Laia
authors.initials: L
authors.lastname: Francàs
authors.forename: Xavier
authors.initials: X
authors.lastname: Sala
authors.forename: Jordi
authors.initials: J
authors.lastname: Benet-Buchholz
authors.forename: Lluís
authors.initials: L
authors.lastname: Escriche
authors.forename: Antoni
authors.initials: A
authors.lastname: Llobet
mesh_terms: D002384:Catalysis; D008024:Ligands; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D011720:Pyrazoles / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D011720:Pyrazoles; D011725:Pyridines; D014867:Water; C009495:titanium dioxide; D012428:Ruthenium; D014025:Titanium; D010100:Oxygen