Auxiliary ligand-induced synthesis of ferrocene-sensitized titanium-oxo clusters with broad light absorption and excellent photoelectric properties

Abstract

The rational design and construction of polyoxotitanium clusters with outstanding photoelectrochemical activity represents a significant challenge in the field. Herein, employing ferrocene as a photosensitizer and incorporating diverse auxiliary ligands, we have successfully constructed a family of structurally varied ferrocene-sensitized polyoxotitanium clusters, formulated as Ti3 (μ3-O) (Fcc)2(OiPr)8 (Ti3Fcc-1, Fcc = ferrocenecarboxylic acid), Ti3 (μ3-O) (Fcc) (L1) (OiPr)8 (Ti3Fcc-2, L1 = 6-amino-m-toluenesulfonic acid), Ti6 (μ3-O)2 (μ2-O) (Fcc)2 (L2)2(OiPr)10 (Ti6Fcc-1, L2 = salicylhydroxamic acid), Ti6 (μ3-O)4(Fcc)2 (L3)2(OiPr)10 (Ti6Fcc-2, L3 = diisopropanolamine), and Ti8 (μ3-O)4(Fcdc)4 (L4)2(OiPr)10 (Ti8Fcdc, Fcdc = 1,1-ferrocenedicarboxylic acid, L4 = triisopropanolamine). The incorporation of auxiliary groups can effectively regulate the structure of ferrocene-functionalized polyoxotitanium clusters, resulting in a gradual growth of the cluster core from Ti3 to Ti6, and ultimately reaching Ti8. Moreover, these titanium-oxo clusters exhibit displayed enhanced visible light absorption and narrow bandgaps, which are primarily attributed to the charge transport from Fcc/Fcdc and ancillary groups to the cluster core. These Ti-oxo clusters were also used as electrode precursors for investigating their photoelectric behaviors and exhibited clear photocurrent responses. This work not only expands ferrocene-sensitized titanium-oxo clusters library, but also provides guidance for the rational design and controllable construction on titanium-based photoactive materials.