| Autor: |
Passadis SS; Section of Inorganic and Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece., Hadjithoma S; Department of Chemistry, University of Cyprus, Nicosia 2109, Cyprus., Siafarika P; Physical Chemistry Laboratory, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece., Kalampounias AG; Physical Chemistry Laboratory, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece.; Institute of Materials Science and Computing, University Research Center of Ioannina (URCI), 45110 Ioannina, Greece., Keramidas AD; Department of Chemistry, University of Cyprus, Nicosia 2109, Cyprus., Miras HN; School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK., Kabanos TA; Section of Inorganic and Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece. |
| Abstrakt: |
The siderophore organic ligand N ,2-dihydroxybenzamide (H 2 dihybe) incorporates the hydroxamate group, in addition to the phenoxy group in the ortho-position and reveals a very rich coordination chemistry with potential applications in medicine, materials, and physical sciences. The reaction of H 2 dihybe with TiCl 4 in methyl alcohol and KOH yielded the tetranuclear titanium oxo-cluster (TOC) [Ti IV 4 (μ-O) 2 (HOCH 3 ) 4 ( μ -Hdihybe) 4 (Hdihybe) 4 ]Cl 4 ∙10H 2 O∙12CH 3 OH ( 1 ). The titanium compound was characterized by single-crystal X-ray structure analysis, ESI-MS, 13 C, and 1 H NMR spectroscopy, solid-state and solution UV-Vis, IR vibrational, and luminescence spectroscopies and molecular orbital calculations. The inorganic core Ti 4 ( μ -O) 2 of 1 constitutes a rare structural motif for discrete Ti IV 4 oxo-clusters. High-resolution ESI-MS studies of 1 in methyl alcohol revealed the presence of isotopic distribution patterns which can be attributed to the tetranuclear clusters containing the inorganic core {Ti 4 ( μ -O) 2 }. Solid-state IR spectroscopy of 1 showed the presence of an intense band at ~800 cm -1 which is absent in the spectrum of the H 2 dihybe and was attributed to the high-energy ν(Ti 2 - μ -O) stretching mode. The ν (C=O) in 1 is red-shifted by ~10 cm -1 , while the ν (N-O) is blue-shifted by ~20 cm -1 in comparison to H 2 dihybe. Density Functional Theory (DFT) calculations reveal that in the experimental and theoretically predicted IR absorbance spectra of the ligand and Ti-complex, the main bands observed in the experimental spectra are also present in the calculated spectra supporting the proposed structural model. 1 H and 13 C NMR solution (CD 3 OD) studies of 1 reveal that it retains its integrity in CD 3 OD. The observed NMR changes upon addition of base to a CD 3 OD solution of 1 , are due to an acid-base equilibrium and not a change in the Ti IV coordination environment while the decrease in the complex's lability is due to the improved electron-donating properties which arise from the ligand deprotonation. Luminescence spectroscopic studies of 1 in solution reveal a dual narrow luminescence at different excitation wavelengths. The TOC 1 exhibits a band-gap of 1.98 eV which renders it a promising candidate for photocatalytic investigations. |
