Titanium-oxo-clusters with dicarboxylates: single-crystal structure and photochromic effect.

Two titanium-oxo-clusters Ti(6)O(4)(o-BDC)(2)(o-BDC(i)Pr)(2)(O(i)Pr)(10) (1) and Ti(6)O(3)(o-BDC)(2)(O(i)Pr)(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 Ti(6) oxo-clusters of 1 and 2 are constructed by two dual corner-missing cube subunit, Ti(3)O(3). The two subunits are linked by double μ(3)-O bridges for 1 and single μ(2)-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 O(2)(•-) 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 H(2)O(2).