4-Chlorosalicylate-stabilized titanium-oxo clusters with structures mediated by tetrazole and their photophysical properties

Abstract

Three 4-chlorosalicylate-stabilized titanium-oxo clusters (TOCs), namely, H2[Ti4(μ2-O)(μ2-OiPr)2(OiPr)6(ClSal)4] (ClSal = 4-chlorosalicylate), H[Ti11(μ3-O)7(μ2-O)2(μ2-OiPr)2(OiPr)9(ClSal)8], and H2[Ti14(μ3-O)8(μ2-O)4(μ2-OiPr)4(OiPr)14(OH2)0.5(ClSal)8]·2H2O were synthesized and structurally characterized by single-crystal X-ray diffraction analysis. It is interesting that tetrazole exhibits structure-directing effect in the reaction between Ti(OiPr)4 and 4-chlorosalicylic acid. The band-gap energies were modulated by different Ti-oxo core structures of these 4-chlorosalicylate-stabilized titanium-oxo clusters. DFT calculations reveal that the ligand-to-core charge transfer (LCCT) from the 4-chlorosalicylate to the cluster core is responsible for the low-energy charge transfer states. The photocurrent response and dye degradation experiments show that the Ti-oxo core structures have significant influence on the photoelectrochemical and photocatalytic properties of these 4-chlorosalicylate-stabilized titanium-oxo clusters.