Assembly of cyclic ferrocene-sensitized titanium-oxo clusters with excellent photoelectrochemical activity

The development of crystalline titanium-oxo clusters has made great progress in recent years. However, the geometric assembly of titanium-oxo clusters is still very challenging. Herein, we report the assembly of two cyclic titanium-oxo clusters with ferrocene connectors, formulated as Ti-12(mu(3)-O)(4)(Fcdc)(4)((OPr)-Pr-i)(32)center dot 0.5CH(2)Cl(2) (Fcdc = 1,1'-ferrocenedicarboxylic acid; Ti(12)Fcdc(4)) and Ti-18(mu(2)-O)(6)(mu(3)-O)(6)(Fcdc)(2)(L1)(2)(L2)(4)((OPr)-Pr-i)(34)center dot 2HO(i)Pr (L1 = isonicotinic acid; L2 = salicylhydroxamic acid; Ti(18)Fcdc(2)). Single-crystal X-ray diffraction studies demonstrate that ferrocene with two carboxylic arms can adhere to the surface of {Ti-6} and/or {Ti-3} units, resulting in fascinating cyclic structures of Ti(12)Fcdc(4) and Ti(18)Fcdc(2). Notably, ferrocene ligands can not only serve as connectors to induce the geometric assembly of Ti-oxo clusters, but can also act as photosensitizers to greatly improve the light absorption behavior of the resulting compounds. Furthermore, the DFT calculation results suggest that the HOMO -> LUMO transition mainly involves ferrocenyl group -> Ti-oxo core charge transfer. Using the two ferrocene-containing clusters as electrode precursors, both electrodes exhibited excellent photocurrent responses. Our work opens a new way for the geometric assembly of titanium-oxo clusters and also contributes to the deep understanding of the structure-property relationships of sensitized Ti-based materials.

Automated summary

This study reports the assembly of two cyclic titanium-oxo clusters with ferrocene connectors and demonstrates that ferrocene ligands can serve as both connectors and photosensitizers to improve the light absorption behavior of the resulting compounds. The research opens a new way for the geometric assembly of titanium-oxo clusters and contributes to the deep understanding of the structure-property relationships of sensitized Ti-based materials.