Tetranuclear Oxo-Titanium Clusters with Different Carboxylate Aromatic Ligands: Optical Properties, DFT Calculations, and Photoactivity.

Titanium(IV) oxo-clusters of the general formula (Ti₄O₂(OiBu)10(O₂CR')₂) (R' = C13H₉ (1), PhCl (2), PhNO₂ (3)) were studied in order to estimate their potential photoactivity. The structure of the resulting tetranuclear Ti(IV) oxo-complexes was then determined via single crystal X-ray diffraction, infrared and Raman spectroscopy, and electron spin resonance (ESR). An analysis of diffuse reflectance spectra (DRS) allowed for the assessment of band gap values of (1)⁻(3) microcrystalline samples complexes. The use of different carboxylate ligands allowed the band gap of tetranuclear Ti(IV) oxo-clusters to be modulated in the range of 3.6 eV⁻2.5 eV. Density functional theory (DFT) methods were used to explain the influence of substitutes on band gap and optical activity. Dispersion of (1)⁻(3) microcrystals in the poly(methyl methacrylate) (PMMA) matrixes enabled the formation of composite materials for which the potential photocatalytic activity was estimated through the study on methylene blue (MB) photodegradation processes in the presence of UV light. The results obtained revealed a significant influence of carboxylate ligands functionalization on the photoactivity of synthesized tetranuclear Ti(IV) oxo-complexes.