The effects of transition-metal doping and chromophore anchoring on the photocurrent response of titanium-oxo-clusters.

Titanium-oxo-clusters (TOCs), [Ti₆O₄(OⁱPr)₁₀(Cat)₂(BA)₂] (1) and [Ti₁₂M₂O₁₀(OEt)₂₂(Cat)₂(BA)₄] (M = Co, Mn, Ni, 2–4; H₂Cat = catechol, HBA = benzoic acid) are prepared in one step in an in situ solvothermal synthesis. Cluster structures of 2–4 can be considered as two 1 moieties merged together by two transition metal atoms. Unlike most TOCs with sphere-like structures, clusters 2–4 feature a unique single layered structure. They are not only transition metal doped TOCs but also charge transfer (CT) TOCs, CT from Cat to the TiO cluster core. Photoelectrodes were prepared by dipping the solution of clusters on a porous TiO₂ substrate. Photocurrent response properties of the electrodes were studied in comparison with those of the electrodes of non-metal doped 1 and the non-Cat coordinated Ti₆ cluster. The results showed that the photocurrent densities of metal doped clusters are higher than that of non-doped clusters and the highest photocurrent density was found for the redox active Co(ii) doped cluster. Charge transfer also plays an effective role in photocurrent conversion under visible light irradiation. [ABSTRACT FROM AUTHOR]