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; COMEDI, DAVID; TIRADO, MONICA; ROMERO, ISABEL; FONTRODONA, XAVIER ; PARELLA, TEODOR; MORÁN VIEYRA. EDUARDO F. ; BORSARELLI, CLAUDIO D. ; KATZ, NÉSTOR E.

INORGANIC CHEMISTRY

AMER CHEMICAL SOC

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 Mebpy-CN ( = 4-methyl-2,2´-bipyridine-4?-carbonitrile) as an auxiliary ligand, of general formula [Ru(bpy)3-x(Mebpy-CN)x](PF6)2 ( x = 1,2,3) (with bpy = 2,2?-bipyridine). A significant increase in lifetime and the 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.