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.