We have shown that Ru-II(bpy)(2)(bpy-4-(xylyl)(x)-drop-phenyl-COOH)(PF6)(2) (abbreviated Rux, where x = 0, 1 or 2 xylyl groups; bpy = 2,2'-bipyridine) dyes can act as sensitizers for nanocrystalline TiO2 in functional photoelectrochemical cells under simulated solar illumination, albeit with low efficiencies. Both the short-circuit photocurrent density and the open-circuit voltage decreased as x was increased. Electron injection (10(6)-10(8) s(-1)) was slightly faster for the x = 0 dye, but both recombination (10(-11)-10(-13) cm(3) s(-1)) and regeneration (10(4)-10(6) s(-1) for 10 mM I-) were slightly faster for the x = 2 dye. We suggest that the lack of distance dependence is due to the flexible one-carboxyl attachment to the surface resulting in the Ru-TiO2 electron-tunneling distance being very similar for x = 0, 1, and 2. For all of the Rux sensitizers, a relatively small potential was needed for generation of current in the dark, indicating that the reaction between electrons in TiO2 and the I-3(-)/I- electrolyte solution is as favorable for the Rux sensitizers as for unmodified TiO2 electrodes.