Chemical and Biomolecular Engineering - Theses
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ItemMannich bases of catechol: their synthesis and complex derivatives with silicon(IV) and aluminium(III)( 2001)The study of coordination chemistry has over the years evoked a great deal of interest from numerous researchers as the basic principles of coordination complexes can be applied to a vast variety of scientific areas. The application of complexes involving metal ions and organic molecules has, for quite some time, been exploited in the hydrometallurgical industry for separation and purification of commercial and precious metals. Silicon(IV) and aluminium(III) are two such metals that have been extensively studied, with particular focus placed on complexes with benzene-1,2-diol (catechol) as it is a very effective coordinating ligand. Whilst there are many examples in the literature of ligands that contain the characteristic 1,2-vic-diol feature of catechol, there are no reports of complexes involving Mannich base derivatives of catechol in relation to potential separation technologies. More specifically, the structures of such complexes formed in anhydrous conditions are novel and have not previously been investigated. The work presented in this thesis is directed towards developing a fundamental understanding of the complexes that catechol and Mannich base derivatives of catechol form with silicon(IV) and aluminium(III) ions in non-aqueous conditions. Future application to separation technologies involving polymeric supports and solvent extraction are also explored and discussed. Initial investigations into coordination of catechol to silicon(IV) ions in aqueous alkaline media using an in situ 13C NMR technique revealed the exclusive formation of the tris-complex irrespective of initial caustic concentrations and molar ratios. Achieving the stoichiometry of this complex may prove to be difficult in a polymeric support incorporating the structure of catechol, such as a novolac type resin. These initial efforts led us to consider more closely the option of solvent extraction. The hydrophilic nature of this tris-complex also renders it unsuitable for application to solvent extraction methods. It was therefore envisaged that through manipulation of the hydrophobic balance in the coordinating catechol ligand, the hydrophobic balance of the resulting complex could be controlled. (For complete abstract open document.)