Amino-Polyalcohol-Solvothermal Synthesis of Titanium-Oxo Clusters: From Ti6 to Ti19 with Structural Diversity

As is known, amino-polyalcohol ligands are usually used as sacrificial agents in photocatalytic reactions. And polyoxo-titanium clusters (PTCs) are molecular modes of titanium dioxide, one of the most important photocatalysts. In order to help understand the intrinsic coordination feature of amino-polyalcohol toward titanium-oxo species, we carried out the research of constructing PTCs with amino-polyalcohol ligands. In view of the low melting point of amino-polyalcohol, they have been directly applied as reaction mediums. Under this new synthetic method, a series of PTCs have been successfully obtained, namely, Ti6(μ2-O)2(OCH2CH2O)2(OiPr)4(dea)6·HOiPr (deaH2 = diethanolamine, PTC-171), Ti9(μ2-O)2(μ3-O)4(tea)2(OiPr)8(dea)5(teaH3 = triethanolamine, PTC-172), Ti11(μ3-O)10(μ4-O)(OiPr)14(dea)4 (PTC-173), Ti19(μ2-O)6(μ3-O)12(dea)18Cl4 (PTC-174), and Ti19(μ2-O)6(μ3-O)12(dea)18(NO3)4·(H2O)6 (PTC-175). Their structures are determined by single-crystal X-ray diffraction analysis. It is worth noting that PTC-174 and PTC-175 are not only the first Ti19 examples of crystalline PTCs, but also currently the largest PTCs compounds in the amino-polyalcohol system. Moreover, the solid-state UV–vis spectra of these PTCs were recorded. And their applications in photocurrent responses were also investigated. This work provides an interesting method for the preparation of amino-polyalcohol base PTCs and would also benefit the mechanism interpretation of the photocatalytic processes of titanium oxide materials.