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Catalytic activities of Metallophthalocyanines towards detection and transformation of pollutants

by Agboola, B.O.

Abstract (Summary)
Syntheses, spectral, electrochemical and spectroelectrochemical studies of new thiolderivatised MPc complexes were satisfactorily carried out. For the first time, spectroelectrochemistry gave evidence for the formation of Ni[superscript 2+]/Ni[superscript +] process in a NiPc complex. Significant insights as to the nature of Fe[superscript +]Pc and Ni[superscript +]Pc spectra were obtained.

Transformations of chlorophenols using chemical and photochemical methods are presented. For cobalt tetrasulphophthalocyanine catalysed oxidation of chlorophenols using hydrogen peroxide as the oxidant, types of oxidation products formed depended on the solvent conditions. Photolysis of aqueous solutions of chlorophenols in the presence of immobilised non-transition metal phthalocyanine photosensitisers onto AmberliteĀ® was carried out. For the first time, MPcS[subscript mix] complexes were immobilised on AmberliteĀ® for use in heterogeneous photocatalysis. Photolysis of the chlorophenols resulted mainly in the formation of chlorobenzoquinone derivatives. The generation of singlet oxygen ([superscipt 1]O[subscript 2]) by these immobilised MPc photosensitisers was found to play a major role in their photoactivities.

Modifications of gold electrodes with the newly synthesised thiol-derivatised MPc complexes via electropolymerisation and SAM technique are presented. Cyclic voltammetry, impedance spectroscopy (NiPcs only) and spectroelectrochemical techniques (NiPcs only) confirmed that the complexes formed films on gold electrodes. Stable and well packed SAM films as evidenced by the voltammetric characterisation were obtained. For the first time, optimisation of the time for SAM formation based on CV technique was studied. First example of a formation of MnPc-SAM was achieved.

Catalytic activities of the NiPc towards chlorophenol depended on the nature of the NiPc in the polymer films and also anti-fouling ability of the films depended on polymer film thickness. The FeTBMPc polymer modified gold electrode showed the best catalytic activity in terms of peak potential, E[subscript p] when compared to reported work in literature for nitrite electrooxidation. Cyclic voltammetry and spectroscopy studies showed that the CoPcs, FePcs and NiPcs catalysed nitrite oxidation involve 2 electrons in total while that of MnPcs involve 1 electron. Better catalytic performance towards sulphite electrooxidation were obtained for the CoPcs, FePcs and MnPcs which have metal based redox processes within the range of the sulphite electrooxidation peak while the NiPcs which did not show metal based oxidation reaction performed less.

Bibliographical Information:

Advisor:

School:Rhodes University

School Location:South Africa

Source Type:Master's Thesis

Keywords:chemistry

ISBN:

Date of Publication:01/01/2007

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