Crystalline bis(η5-cyclopentadienyl)bis(benzoato/carboxylato)titanium(IV) precursor-directed route to functional titanium dioxide nanomaterials
Five titanocene(IV) carboxylates of the general formula Cp2Ti(O2CR)2 viz., [Ti(η5-C5H5)2(O2CC6H5-4-CH3)2] (1), [Ti(η5-C5H5)2(O2CC4H3-2-O)2] (2), [Ti(η5-C5H5)2(O2CC4H3-3-O)2] (3), [Ti(η5-C5H5)2(O2CC(CH3)3)2] (4), and [Ti(η5-C5H5)2(O2C(CH)C(CH3)3)2] (5) have been synthesized. All the titanocene(IV) carboxylates have been characterized by IR, 1H, and 13C NMR spectroscopic techniques, and the crystal and molecular structures of 1–5 have been determined by single crystal X-ray crystallography. The structures present similar features with monodentate carboxylate ligands and tetrahedral Ti centers, assuming that each cyclopentadienyl (Cp) ring occupies one position only. The differences in the structures relate primarily to the relative orientations of the carboxylate ligands. In the molecular packing, non-conventional Cp-C–H···O(carbonyl) hydrogen bonds are observed in each case and lead to supramolecular chains in each of 1, 4, and 5. In 2, the 2-furyl-O atoms also participate in C–H···O interactions leading to a two-dimensional array. Finally, in 3, a two-dimensional array arises as a result of Cp-C–H···O(carbonyl) and 3-furyl-C–H···O(carbonyl) interactions. As representative example, 3 was used as starting material for the synthesis of TiO2 nanoparticles (NPs). An effective and simple wet-chemical method involving calcination and ultrasonication is suggested for obtaining pure anatase TiO2 NPs, which were confirmed from the powder XRD and imaging techniques such as SEM, TEM, and EDS.
