Catalytic behavior of osmium (II), rhodium (III) and ruthenium (II) Phthalocyanines towards the electrooxidation of cysteine on glassy carbon electrodes
- Authors: Sekota, Mantoa , Nyokong, Tebello
- Date: 1997
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293290 , vital:57072 , xlink:href=" https://doi.org/10.1002/elan.1140091608"
- Description: Glassy carbon electrodes (GCE's) modified with phthalocyanine complexes of Rh, Ru and Os are employed for the catalytic oxidation of cysteine. When cyanide and dimethylsulfoxide (DMSO) are used as axial ligands giving (DMSO)(Cl)RhIIIPc, [(CN)2RhIIIPc]−, (DMSO)2OsPcII, and [(DMSO)2Ru(II)Pc]·2DMSO complexes, the peak currents for the oxidation of cysteine increase after each scan, indicating an increase in the catalytic activity of the electrode with repetitive scanning. This improvement in the catalytic activity of the GCE after the first scan is attributed to the formation of dimeric π cation radical species at the electrode surface.
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- Date Issued: 1997
The study of the interactions of cobalt (II) tetrasulfophthalocyanine with cysteine and histidine
- Authors: Sekota, Mantoa , Nyokong, Tebello
- Date: 1997
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293458 , vital:57087 , xlink:href="https://doi.org/10.1016/S0277-5387(97)00096-X"
- Description: Kinetics for the interaction of cobalt(II) tetrasulfophthalocyanine ([CoIITSPc]4−, Pc(−2) = phthalocyanine dianion) with the amino acids, histidine and cysteine, in pH 7.2 phosphate buffer were studied. The rates were found to be first order in both the [CoIITSPc]4− and the amino acid. The formation of the [CoIIITSPc]3− species in the presence of histidine occurred with a rate constant of 0.16 dm3 mol−s−1, whereas the formation of the [CoITSPc]5− species in the presence of cysteine gave a rate constant of 2.2 dm3 mol−1.
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- Date Issued: 1997
Cyclic voltammetry and spectroelectrochemistry of osmium phthalocyanines in aqueous and non-aqueous solvents
- Authors: Sekota, Mantoa , Nyokong, Tebello
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293358 , vital:57078 , xlink:href="https://doi.org/10.1016/0277-5387(95)00581-1"
- Description: Cyclic voltammetry of osmium phthalocyanine complexes, [(CN)2OsIIPc]2− and (py)2OSIIPc (PC = phthalocyanine dianion), show two oxidation couples and two reduction couples in acetonitrile and dimethy1formamide. Oxidation and reduction in these complexes occur at the ring to form cation and anion radical species, respectively. The [(CN)2OsIIPC]2− complexes show a remarkable ease of ring oxidation with oxidation potentials that are much lower than is typical for metallophthalocyanines. Half-wave potentials of 0.25 and 0.67 V (versus saturated calomel electrode, SCE) were obtained for the first and second ring oxidations, respectively. The [(CN)2OSIIPc]2− complex is soluble in water at pHs greater than 4. This complex shows one oxidation couple in pH 9 buffer at −0.11 V versus SCE.
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- Date Issued: 1996