Improving the Photosensitizing Properties of Ruthenium Polypyridyl Complexes Using 4-Methyl-2,2'-bipyridine-4'-carbonitrile as an Auxiliary Ligand

J.H.M. ORTIZ; N. C. VEGA; D. COMEDI; M. TIRADO; I. ROMERO; X. FONTRODONA; T. PARELLA; F. E. M. VIEYRA; C. D. BORSARELLI; N. E. KATZ

INORGANIC CHEMISTRY

AMER CHEMICAL SOC

Lugar: Washington; Año: 2013 vol. 52 p. 4950 - 4962

0020-1669

We report in this work the synthesis and spectroscopic, electrochemical, spectroelectrochemical, and photophysical characterization of a novel series of ruthenium polypyridyl complexes with 4-methyl-2,2′-bipyridine-4′-carbonitrile (Mebpy-CN) as an auxiliary ligand of general formula[Ru(bpy)3−x(Mebpy-CN)x](PF6)2(x=1−3) (with bpy = 2,2′-bipyridine). A significant increase in the lifetime and quantum yield of emission of the lowest 3MLCT excited state is disclosed when going from x=1 to x= 3, evidencing an improvement of the photosensitizing properties with respect to [Ru(bpy) 3]-(PF6)2. Furthermore, quenching by molecular oxygen of 3MLCT excited statesof the three complexes produced singlet molecular oxygen (1O2) with quantum yield values higher than that of [Ru(bpy)3]2+ in CH3CN. The structure of the complex with x= 1 has been determined by X-ray diffraction. The photoconductivity of ZnO nanowires covered with this same complex is increased by an order of magnitude, pointing to its feasibility as a component of a DSSC. A new dinuclear complex with Mebpy-CN as a bridging ligand has also been prepared and characterized by physicochemical techniques. The derived mixed-valent species of formula [(bpy)2 RuII(Mebpy-CN)RuIII(NH3)5]5+dis-plays a considerable metal−metal electronic coupling due to the delocalization effect of a nitrile group in the 4′ position of the bpy ring.