Syntheses, crystal structures and photocatalytic properties of homometallic and heterometallic titanium-oxo clusters

Two new titanium-oxo clusters, named [Ti6(bpdc)2(μ2-O)(μ3-O)2(iPrO)14] (1) and [Ti4Zn8(bpdc)8(μ3-O)8(dma)2(iPrOH)2·4DMF·2iPrOH] (2) (H2bpdc = 2, 2′-biphenyl -dicarboxylic acid, dma = dimethylamine, and DMF = N,N′-dimethylformamide), have been successfully synthesized and characterized. Single crystal diffraction shows that compound 1 features a Ti6 core based on two coplanar trinuclear Ti3-subunits linked by two carboxylic ligands. Compound 2 possesses a heterometallic Ti4Zn8 core based on a central Ti4 subunit and eight neighboring zinc(II) ions in the presence of eight carboxylic ligands. The estimated narrow optical bandgaps of compounds 1 and 2 are 3.07 and 3.05 eV, respectively. Furthermore, compounds 1 and 2 exhibit much higher and more efficient photocatalytic degradation abilities for rhodamine B than TiO2 under visible light irradiation.