Date of Award
Doctor of Philosophy (PhD)
Chemistry & Biochemistry
James W. Lee
Transition metal complexes with Schiff base ligands offer a wide application in the field of development of catalysis and material. The straightforward synthesis allowed the structural modification and helped to optimize in various application of such complexes. Titanium-containing complexes have been reported to be important for their catalytic and material applications through the coordination of a tetradentate Schiff base ligand, viz. N, N’-ethylene bis(salicylideneiminate) dianion (salen). Studies reporting the characterization of achiral titanium(IV) salen complexes are scarce due to their intricate nature. Such complexes would be comparatively less expensive and easier to prepare synthetically and thus could represent an excellent alternative to the more expensive chiral titanium(IV) complexes. Our research group designed a series of octahedral titanium(IV) Schiff base complexes along with various substituted phenols as ligands, which were assessed for their purity and characterized using various methods and spectroscopic techniques such as elemental analysis, electrochemistry, UV-visible, 1H, 13C, 19F, and 49Ti NMR and FTIR spectroscopies. From the elemental analysis data, the complexes were proposed to have the general structural formula [Ti(salen)OPh-X)2] (where X = F, NO2 and CH3). The 49Ti-NMR spectral data showed chemical shifts in the range of +1160 ppm to +1170 ppm, which demonstrated that the magnetic environment showing an increase in the linewidth with molecular size for the particular titanium(IV) salen complex due to the presence of salen ligand.
Another study was focused on the preparation of liquid crystal material using Schiff base ligand and the first-row transition metal ions. To exhibit the liquid crystal property, the design of the ligand plays a vital role. Herein, we used 2,4-dihydroxybenzaldehyde to prepare precursor ligand, at the reactive para-position, the alkoxybenzyl attached to generate precursor aldehyde. Ortho-phenylenediamine was used to create novel tetradentate rigid core ligand with flexible alkoxy side chains. These ligands coordinate with Co(II), Ni(II), and Cu(II) metal ions resulting in square planar Schiff base complexes. This thesis is focused on the preparation of stable, pure, and well characterized liquid crystal complexes. Various methods were explored, optimizing the yield and purity. Mesomorphic behavior of the complexes was explored optically, thermally, and by using XRD techniques.
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Gurung, Raj K..
"Synthesis, Characterization, Spectroscopic, and Mesomorphic Studies of New Schiff Base Ligands and Titanium, Cobalt, Nickel and Copper Metal Centers"
(2020). Doctor of Philosophy (PhD), Dissertation, Chemistry & Biochemistry, Old Dominion University, DOI: 10.25777/067q-ga23