An acetylacetonate-based semiconductor-sensitizer linkage

Coordination compounds of the general type Ru(dmb)(2)(LL)(PF6)(2), where dmb is 4,4'-(CH3)(2)-2,2'-bipyridine and LL is 4-(CH3)-4'-(COOH)-2,2'-bipyridine, or 4-(CH3)-4'-((CH2)(3)COOH)-2,2'-bipyridine, or 4-(CH3)-4'-((CH2)(3)-COCH2COOC2H5)-2,2'-bipyridine were prepared for the attachment to semiconductor metal oxide surfaces. The optical and redox properties of these compounds in dichloromethane solution are reported. Binding to porous nanostructured TiO2 films was analyzed with the Langmuir adsorption isotherm model. Photoelectrochemical measurements of the modified TiO2 electrodes in regenerative solar cells are reported. The results indicate that intimate electronic coupling between the surface link and the chromophoric ligand is not a strict requirement in the design of sensitizers for photovoltaic applications. Interfacial kinetics for recombination of the electron in the solid with the oxidized form of the sensitizer were quantitated by excited state absorption spectroscopy.