Show simple item record

dc.contributor.advisor Thomas, M.S.
dc.contributor.advisor Darkwa, J.
dc.contributor.advisor Gelebe, A.C. Sebati, Ngwanamohuba Wilhemina Ngwanamohuna Wilhemina 2016-05-12T13:11:04Z 2016-05-12T13:11:04Z 2014
dc.description Thesis (MSc. (Chemistry)) --University of Limpopo, 2014 en_US
dc.description.abstract This study deals with the synthesis and characterisation of cobalt complexes of nitrogen-donor imidazolyl- salicylaldimine ligands and their potential catalytic activity in the oxidation reactions of phenol and styrene. Five ligands were used in the study, four of which are new. Compound 2,4-di-tert-butyl-6{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L1), was synthesised according to a literature procedure. The other imidazole-based salicylaldimine compounds 2-ethoxy-6{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L2), 4-methoxy-6{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L3), 1{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-benzene (L4) and 4-methyl-1{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-benzene (L5) were prepared by Schiff base condensation reaction of histamine dihydrochloride with 3-ethoxy-2-hydroxybenzaldehyde, 5-methoxy-2-hydroxybenzaldehyde, benzaldehyde, 4-methylbenzaldehyde respectively. L1-L5 were characterised by 1H and 13C{1H} NMR, IR and UV-vis spectroscopy and high resolution mass spectrometry (HRMS). Reactions of L1-L5 with CoCl2 yielded complexes C1-C5, while complexes C6-C10 were synthesised by reactions of L1-L5 with CoBr2 all in a ratio of 1:1 of ligand to metal precursor. The cobalt(II) complexes were characterised by IR and UV-vis spectroscopy, elemental analysis and high resolution mass spectrometry due to their paramagnetic nature. All the characterisation data point to complexes C1-C10 being formulated as [Co(3-L)X] (where L = ligand and X = halide). However, single crystal X-ray diffraction showed that the prolonged stay of complex C6 in a solution gave a new structure as complex C11. The imidazole-based salicylaldimine cobalt(II) complexes (C1-C10) were tested as catalysts for the oxidation reactions of phenol and styrene with H2O2, O2 and 3-chloroperbenzoic acid as oxidants. The complexes were found not to be active for the oxidation of both substrates (phenol and styrene) with 0% conversion, even when the reactions were left for 1 week. Analysis of the oxidation reactions were performed with GC and 1H NMR spectroscopy. Both analysis methods showed the presence of unreacted substrates at the end of the reaction period. Effects of concentration of pre-catalysts, substrates and oxidants, time and temperature of reaction and nature of solvent on catalytic activity were also investigated, however the conversions remained at 0% conversion. en_US
dc.format.extent xiv,101 leaves en_US
dc.language.iso en en_US
dc.publisher University of Limpopo en_US
dc.relation.requires pdf version en_US
dc.subject Cobalt(II)-Imidazolyl complexes en_US
dc.subject Oxidation en_US
dc.subject Phenol en_US
dc.subject Styrene en_US
dc.subject.lcsh Chemistry -- South Africa en_US
dc.title Synthesis and characterisation of cobal (II)- imidazolyl complexes as potential catalysts in the oxidation of phenol and styrene en_US
dc.type Thesis en_US

Files in this item

This item appears in the following Collection(s)

Show simple item record

Search ULSpace


My Account