Improving the photosensitizing properties of ruthenium polypyridyl complexes by using 4-methyl-2,2?-bipyridine-4?-carbonitrile as an auxiliary ligand

MECCHIA ORTIZ, JUAN; VEGA, NADIA CELESTE; COMEDI, DAVID MARIO; TIRADO, MONICA CECILIA; ROMERO, ISABEL; FONTRODONA, XAVIER; PARELLA, TEODOR; MORAN VIEYRA, FAUSTINO; BORSARELLI, CLAUDIO; KATZ, NÉSTOR

INORGANIC CHEMISTRY

AMER CHEMICAL SOC

Lugar: Washington; Año: 2013

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 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 respect to [Ru(bpy)3](PF6)2. Furthermore, quenching by molecular oxygen of 3MLCT excited states of 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)2RuII(Mebpy-CN)RuIII(NH3)5]5+, displays a considerable metalmetal electronic coupling due to the delocalization effect of a nitrile group in the 4?- position of the bpy ring.