Ferrocene-sensitized titanium-oxo clusters with effective visible light absorption and excellent photoelectrochemical activity

Abstract

Sensitized Ti-oxo clusters have attracted growing attention as analogous molecular model compounds of dye-sensitized titanium dioxide solar cells. However, reports on the introduction of metal complexes as photosensitizers into Ti-oxo clusters are still very rare. Herein, with the use of an organometallic complex ferrocene as a sensitizer, two novel ferrocene-sensitized Ti-oxo clusters, namely, [Ti₈(μ₃-O)₄(Dipa)₂(Fcdc)₄(OⁱPr)₁₀]·2HOⁱPr (H₂Fcdc = 1,1-ferrocene dicarboxylic acid, Dipa = diisopropanolamine, and HOⁱPr = isopropanol, Ti₈Fcdc₄) and [Ti₁₀(μ₄-O)₂(μ₃-O)₄(Fcdc)₂(μ₂-OEt)₈(OEt)₁₀]·2HOEt (Ti₁₀Fcdc₂) have been successfully synthesized. Their molecular structures, light absorption, charge transfer, and photoelectrochemical properties were systematically investigated. It is demonstrated that the incorporation of Fcdc ligands shows a significant influence on the light absorption of the resulting clusters, and their absorption band edge is extended to about 580 nm. Furthermore, experimental measurements and theoretical calculations showed that the intense intramolecular charge transfer occurs from the Fcdc ligands to the Ti-oxo core. Based on these advantages, clusters Ti₈Fcdc₄ and Ti₁₀Fcdc₂ were used as photoelectrode precursors to carry out photoelectrochemical experiments, and both exhibited clear photocurrent responses. The molecular structure, light absorption, and effective charge transfer of materials have a direct bearing on their photoelectrochemical performances. This work not only provides novel structural models for sensitized Ti-oxo clusters towards the modulation of photoelectric properties but also provides new insights into further understanding the structure–property relationships of sensitized clusters.