Titanium–oxo–Clusters with Dicarboxylates: Single-Crystal Structure and Photochromic Effect

Two titanium-oxo-clusters Ti6O4(o-BDC)2(o-BDCiPr)2(OiPr)10 (1) and Ti6O3(o-BDC)2(OiPr)14 (2) (BDC = benzene dicarboxylate) were prepared by one-step in situ solvothermal synthesis. The compounds are the rare examples of the dicarboxylate-substituted titanium-oxo-clusters. Their crystal structures are successfully measured by single-crystal X-ray analysis. The Ti6 oxo-clusters of 1 and 2 are constructed by two dual corner-missing cube subunit, Ti3O3. The two subunits are linked by double μ3–O bridges for 1 and single μ2–O bridge for 2, respectively, and the latter is a new type of carboxylate substituted titanium-oxo-cluster. A photochromic effect was observed upon irradiation of the crystals in the presence of alcohol. The light irradiation changed the color of the crystals from transparent to purple-gray. The Ti­(III) signal was detected after the irradiation, and when the sample was exposured in air, superoxide diatomic O2• – radical was found. Photodegradation of the methyl orange in aqueous dispersions of microcrystals of the cluster 2 was carried out under UV cut white light with the assistance of H2O2.