A Series of Ti6 Oxo Clusters Anchored with Arylamine Dyes: Effect of Dye Structures on Photocurrent Responses.

Abstract

Dye molecules pre-anchored on titanium oxo clusters (dye-TOCs) are attractive as model compounds of dye-sensitized titanium oxide. To investigate the effects of the dye ligand structures of the dye-TOCs on photocurrent conversion, a series of dye-TOCs with the same Ti6 core structure and different antenna ligands (L) was synthesized and characterized crystallographically. The TOCs have the same structural formula of [Ti6 O4 L2 (O3 PPh)2 (OiPr)10 ]. Two types of dyes with para- or meta-substituted structures were designed and used as the ligands. The results show that charge transfer from the donor group to the TiO core of the TOCs with the para-substituted ligands is stronger than those with the meta-substituted ligands. The steric effect of the ligands also greatly influences the photocurrent density. Larger branched structures of the dye ligands reduce the coverage density of the dye-TOCs on TiO2 electrodes and also weaken the effective covalent bonding of the dye-TOCs on the electrode, and consequently, the photocurrent is decreased.