Iron perchlorophthalocyanine and tetrasulfophthalocyanine catalyzed oxidation of cyclohexane using hydrogen peroxide, chloroperoxybenzoic acid and tert-butylhydroperoxide as oxidants
- Grootboom, Natasha, Nyokong, Tebello
- Authors: Grootboom, Natasha , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289606 , vital:56653 , xlink:href="https://doi.org/10.1016/S1381-1169(01)00404-6"
- Description: Polychlorophthalocyanine (Cl16PcFeII) and tetrasulfophthalocyanine ([FeIITSPc]4−) complexes of iron are employed as catalysts for the oxidation of cyclohexane using tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid (m-CPBA) and hydrogen peroxide as oxidants. Catalysis using the Cl16PcFeII was performed in a dimethylformamide:dichloromethane (3:7) solvent mixture. For the [FeIITSPc]4−catalyst, a water:methanol (1:9) mixture was employed. The products of the catalysis are cyclohexanone, cyclohexanol and cyclohexanediol. The relative yields of the products depended on oxidant and the catalyst. TBHP was found to be the best oxidant since minimal destruction of the catalyst and higher selectivity in the products were observed when this oxidant was employed. The mechanism of the oxidation of cyclohexane in the presence of the Cl16PcFeII and [FeIITSPc]4− involves the oxidation of these catalysts, forming an Fe(III) phthalocyanine species as an intermediate. Higher yields were observed when [FeTSPc]4− was employed as a catalyst, which is more soluble than the perchlorinated iron phthalocyanine catalyst.
- Full Text:
- Date Issued: 2002
- Authors: Grootboom, Natasha , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289606 , vital:56653 , xlink:href="https://doi.org/10.1016/S1381-1169(01)00404-6"
- Description: Polychlorophthalocyanine (Cl16PcFeII) and tetrasulfophthalocyanine ([FeIITSPc]4−) complexes of iron are employed as catalysts for the oxidation of cyclohexane using tert-butyl hydroperoxide (TBHP), m-chloroperoxybenzoic acid (m-CPBA) and hydrogen peroxide as oxidants. Catalysis using the Cl16PcFeII was performed in a dimethylformamide:dichloromethane (3:7) solvent mixture. For the [FeIITSPc]4−catalyst, a water:methanol (1:9) mixture was employed. The products of the catalysis are cyclohexanone, cyclohexanol and cyclohexanediol. The relative yields of the products depended on oxidant and the catalyst. TBHP was found to be the best oxidant since minimal destruction of the catalyst and higher selectivity in the products were observed when this oxidant was employed. The mechanism of the oxidation of cyclohexane in the presence of the Cl16PcFeII and [FeIITSPc]4− involves the oxidation of these catalysts, forming an Fe(III) phthalocyanine species as an intermediate. Higher yields were observed when [FeTSPc]4− was employed as a catalyst, which is more soluble than the perchlorinated iron phthalocyanine catalyst.
- Full Text:
- Date Issued: 2002
pH study of the electrocatalytic SO2 detection at a glassy carbon electrode modified with iron (II) tetrasulfophthalocyanine
- Thamae, Mamothibe, Westbroek, Philippe, Nyokong, Tebello
- Authors: Thamae, Mamothibe , Westbroek, Philippe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/304786 , vital:58490 , xlink:href="https://doi.org/10.1007/s00604-002-0914-8"
- Description: The electrocatalytic determination of SO2 is studied as a function of pH at a glassy carbon electrode modified with iron(II)tetrasulfophthalocyanine ([Fe(II)TSPc]4−). It was found in the literature that depending on pH, SO2·xH2O, HSO3 − and/or SO3 2− are the main compounds in solution, that these compounds behave differently at the electrode surface, and that the condition of the electrode surface is stable over the entire pH-range. The use of SO2(g) or sodium sulfite as starting material did result in identical curves except in the pH range from 7.5–9.0. A possible explanation could be given by proposing that SO2·xH2O is very unstable in the presence of SO3 2−. In strongly acidic medium, SO2·xH2O is the main compound, which can be oxidized as well as reduced with exchange of two electrons. HSO3 − is the main compound at pH = 4 and can also be oxidized and reduced with exchange of, respectively, two and four electrons. In alkaline solution sulfite is the main compound and can only be oxidized, also under exchange of two electrons. Detection limits are in the range of 4.0 ± 0.1 × 10−5 and 7.5 ± 0.1 × 10−5 mol L−1, dependent of pH and of the type of reaction (oxidation or reduction) used.
- Full Text:
- Date Issued: 2002
- Authors: Thamae, Mamothibe , Westbroek, Philippe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/304786 , vital:58490 , xlink:href="https://doi.org/10.1007/s00604-002-0914-8"
- Description: The electrocatalytic determination of SO2 is studied as a function of pH at a glassy carbon electrode modified with iron(II)tetrasulfophthalocyanine ([Fe(II)TSPc]4−). It was found in the literature that depending on pH, SO2·xH2O, HSO3 − and/or SO3 2− are the main compounds in solution, that these compounds behave differently at the electrode surface, and that the condition of the electrode surface is stable over the entire pH-range. The use of SO2(g) or sodium sulfite as starting material did result in identical curves except in the pH range from 7.5–9.0. A possible explanation could be given by proposing that SO2·xH2O is very unstable in the presence of SO3 2−. In strongly acidic medium, SO2·xH2O is the main compound, which can be oxidized as well as reduced with exchange of two electrons. HSO3 − is the main compound at pH = 4 and can also be oxidized and reduced with exchange of, respectively, two and four electrons. In alkaline solution sulfite is the main compound and can only be oxidized, also under exchange of two electrons. Detection limits are in the range of 4.0 ± 0.1 × 10−5 and 7.5 ± 0.1 × 10−5 mol L−1, dependent of pH and of the type of reaction (oxidation or reduction) used.
- Full Text:
- Date Issued: 2002
Employee ownership in the context of globalisation: a developing country perspective
- NALEDI
- Authors: NALEDI
- Date: 2002
- Subjects: NALEDI
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/153882 , vital:39532
- Description: This paper represents an initial set of ideas focused on employee ownership within the developing country context. The central question being explored is ‘To what extent can employee ownership support the broader goal of poverty reduction in South Africa (and, by extension, in the developing country context)?’. This is a rather broad question, and as such this note sets out to begin the discussion on this question, rather than seek to provide a definite set of answers. The critical perspectives put forward in this note draw heavily on experiences and debates in South Africa, and particularly those within the labour movement.
- Full Text:
- Date Issued: 2002
- Authors: NALEDI
- Date: 2002
- Subjects: NALEDI
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/153882 , vital:39532
- Description: This paper represents an initial set of ideas focused on employee ownership within the developing country context. The central question being explored is ‘To what extent can employee ownership support the broader goal of poverty reduction in South Africa (and, by extension, in the developing country context)?’. This is a rather broad question, and as such this note sets out to begin the discussion on this question, rather than seek to provide a definite set of answers. The critical perspectives put forward in this note draw heavily on experiences and debates in South Africa, and particularly those within the labour movement.
- Full Text:
- Date Issued: 2002
Effects of axial ligands on the photophysical properties of silicon octaphenoxyphthalocyanine
- Maree, M David, Nyokong, Tebello, Suhling, Klaus, Phillips, David
- Authors: Maree, M David , Nyokong, Tebello , Suhling, Klaus , Phillips, David
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289582 , vital:56651 , xlink:href="https://doi.org/10.1142/S1088424602000452"
- Description: The photochemistry and photophysics of six axially substituted silicon phthalocyanines are reported and show the importance of the axial groups in the photochemistry of these compounds. The fluorescence quantum yields are especially affected by the axial ligand. A very good correlation was found for the experimentally determined fluorescence lifetimes and the theoretically determined lifetimes using the Strickler-Berg equation for the unaggregated molecules.
- Full Text:
- Date Issued: 2002
- Authors: Maree, M David , Nyokong, Tebello , Suhling, Klaus , Phillips, David
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289582 , vital:56651 , xlink:href="https://doi.org/10.1142/S1088424602000452"
- Description: The photochemistry and photophysics of six axially substituted silicon phthalocyanines are reported and show the importance of the axial groups in the photochemistry of these compounds. The fluorescence quantum yields are especially affected by the axial ligand. A very good correlation was found for the experimentally determined fluorescence lifetimes and the theoretically determined lifetimes using the Strickler-Berg equation for the unaggregated molecules.
- Full Text:
- Date Issued: 2002
Voltammetric detection of vitamin B1 at carbon paste electrodes and its determination in tablets
- Oni, Joshua, Westbroek, Philippe, Nyokong, Tebello
- Authors: Oni, Joshua , Westbroek, Philippe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289692 , vital:56663 , xlink:href="https://doi.org/10.1002/1521-4109(200209)14"
- Description: The voltammetric behavior of vitamin B1 in alkaline medium at carbon paste electrode (CPE) is discussed. A method based on cyclic voltammetry for the determination of vitamin B1 at carbon paste electrode modified with manganese phthalocyanine (MnPc-CPE) is presented. In pH 10 buffer, the modified electrode showed catalytic activity towards the oxidation of vitamin B1 by considerably increasing the oxidation current of one of the observed waves compared to the oxidation current obtained at an unmodified electrode. The modified electrode was stable towards the determination of vitamin B1 compared to the unmodified electrode that is completely poisoned after a few scans. A linear relationship between the oxidation current and the concentration of vitamin B1 in solution was observed. The detection limit for vitamin B1 at the modified electrode was of the order of 10−5 mol dm−3. Commercial vitamin B1 tablets were analyzed using the modified electrodes.
- Full Text:
- Date Issued: 2002
- Authors: Oni, Joshua , Westbroek, Philippe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289692 , vital:56663 , xlink:href="https://doi.org/10.1002/1521-4109(200209)14"
- Description: The voltammetric behavior of vitamin B1 in alkaline medium at carbon paste electrode (CPE) is discussed. A method based on cyclic voltammetry for the determination of vitamin B1 at carbon paste electrode modified with manganese phthalocyanine (MnPc-CPE) is presented. In pH 10 buffer, the modified electrode showed catalytic activity towards the oxidation of vitamin B1 by considerably increasing the oxidation current of one of the observed waves compared to the oxidation current obtained at an unmodified electrode. The modified electrode was stable towards the determination of vitamin B1 compared to the unmodified electrode that is completely poisoned after a few scans. A linear relationship between the oxidation current and the concentration of vitamin B1 in solution was observed. The detection limit for vitamin B1 at the modified electrode was of the order of 10−5 mol dm−3. Commercial vitamin B1 tablets were analyzed using the modified electrodes.
- Full Text:
- Date Issued: 2002
Study South Africa
- International Education Association of South Africa (IEASA), Mason, Andy
- Authors: International Education Association of South Africa (IEASA) , Mason, Andy
- Date: 2002
- Subjects: Education, Higher -- South Africa , Education and globalization -- South Africa Student mobility -- Africa International education -- South Africa Education, Higher -- International cooperation , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/65310 , vital:28744 , ISBN 0620247290
- Description: [Message from the Honorable Minister of Education, Prof. Kader Asmal]: Once again I am pleased to provide a message of support for the Guide to South African Universities and Technikons, particularly at a time when we are embarking on a new era with our plans for Higher Education in South Africa. Increasingly we have become aware of the need for higher education graduates who can make a significant contribution to the reconstruction and development of our country and, in this period of globalisation, the rest the world. With the dawn of a new century we need also to ensure that our system of higher education is relevant to the challenges we face in the years ahead. The onset of the 21st century has brought Minister of Education changes in the social, cultural and economic relations spawned by the revolution in information and communications technology. At the centre of these changes is the notion that in the 21st century, knowledge and the processing of information will be the key driving forces for wealth creation and social and economic development. Therefore we are driven by government policy that recognises the importance of human resource development. This involves the mobilisation of human talent and potential through lifelong learning, to contribute to the social, economic, cultural and intellectual life of a rapidly changing society. We need high-level skills training to provide the human resources to strengthen our region's enterprises, services and infrastructure. This requires the development of professionals and knowledge workers with globally equivalent skills, but who are socially responsible and conscious of their role in contributing to development efforts and social transformation. Finally we need to ensure the production, acquisition and application of new knowledge. This is essential for growth and competitiveness, and in turn is dependent on continuous technological improvement and innovation driven by a well-organised, vibrant research and development system which integrates the research and training capacity of higher education with the needs of industry and social reconstruction. Graduates from our higher education institutions have consistently shown that the quality of the education they receive is of a world class standard. Indeed, many developed countries try to lure our graduates away to work in their countries. Increasingly international students have recognised the value of our education system and are choosing to study in South Africa. We welcome them not only to our educational institutions but also to our beautiful country and the vibrant society that South Africa is today. , 2nd Edition
- Full Text:
- Date Issued: 2002
- Authors: International Education Association of South Africa (IEASA) , Mason, Andy
- Date: 2002
- Subjects: Education, Higher -- South Africa , Education and globalization -- South Africa Student mobility -- Africa International education -- South Africa Education, Higher -- International cooperation , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/65310 , vital:28744 , ISBN 0620247290
- Description: [Message from the Honorable Minister of Education, Prof. Kader Asmal]: Once again I am pleased to provide a message of support for the Guide to South African Universities and Technikons, particularly at a time when we are embarking on a new era with our plans for Higher Education in South Africa. Increasingly we have become aware of the need for higher education graduates who can make a significant contribution to the reconstruction and development of our country and, in this period of globalisation, the rest the world. With the dawn of a new century we need also to ensure that our system of higher education is relevant to the challenges we face in the years ahead. The onset of the 21st century has brought Minister of Education changes in the social, cultural and economic relations spawned by the revolution in information and communications technology. At the centre of these changes is the notion that in the 21st century, knowledge and the processing of information will be the key driving forces for wealth creation and social and economic development. Therefore we are driven by government policy that recognises the importance of human resource development. This involves the mobilisation of human talent and potential through lifelong learning, to contribute to the social, economic, cultural and intellectual life of a rapidly changing society. We need high-level skills training to provide the human resources to strengthen our region's enterprises, services and infrastructure. This requires the development of professionals and knowledge workers with globally equivalent skills, but who are socially responsible and conscious of their role in contributing to development efforts and social transformation. Finally we need to ensure the production, acquisition and application of new knowledge. This is essential for growth and competitiveness, and in turn is dependent on continuous technological improvement and innovation driven by a well-organised, vibrant research and development system which integrates the research and training capacity of higher education with the needs of industry and social reconstruction. Graduates from our higher education institutions have consistently shown that the quality of the education they receive is of a world class standard. Indeed, many developed countries try to lure our graduates away to work in their countries. Increasingly international students have recognised the value of our education system and are choosing to study in South Africa. We welcome them not only to our educational institutions but also to our beautiful country and the vibrant society that South Africa is today. , 2nd Edition
- Full Text:
- Date Issued: 2002
Language as a ‘resource’ in South Africa: the economic life of language in a globalising society
- Authors: Wright, Laurence
- Date: 2002
- Language: English
- Type: text , article
- Identifier: vital:7035 , http://hdl.handle.net/10962/d1007370 , https://doi.org/10.1080/10131750285310031
- Description: preprint , We need to develop a much more refined and specific understanding of what is meant when people refer to language is a ‘resource’. If something can accurately be described as a resource, then by its very nature it carries with it or attracts, at least in potential, the social motivation associated with the utilization, development or exploitation of that resource. This is strikingly true where language is the resource in question, because language is so intimately bound up with human activity. Where it exists, such social motivation can be augmented and supported so as to realize the ends of language policy. Contrastingly, where it is seen that social motivation informing a particular language situation is at odds with the intent of language policy, then either implementation must retreat and move to other arenas, other points of influence, where intervention can be more effective, or those charged with implementation must resign themselves to costly and messy efforts to force unwanted change through legal authority.
- Full Text:
- Date Issued: 2002
- Authors: Wright, Laurence
- Date: 2002
- Language: English
- Type: text , article
- Identifier: vital:7035 , http://hdl.handle.net/10962/d1007370 , https://doi.org/10.1080/10131750285310031
- Description: preprint , We need to develop a much more refined and specific understanding of what is meant when people refer to language is a ‘resource’. If something can accurately be described as a resource, then by its very nature it carries with it or attracts, at least in potential, the social motivation associated with the utilization, development or exploitation of that resource. This is strikingly true where language is the resource in question, because language is so intimately bound up with human activity. Where it exists, such social motivation can be augmented and supported so as to realize the ends of language policy. Contrastingly, where it is seen that social motivation informing a particular language situation is at odds with the intent of language policy, then either implementation must retreat and move to other arenas, other points of influence, where intervention can be more effective, or those charged with implementation must resign themselves to costly and messy efforts to force unwanted change through legal authority.
- Full Text:
- Date Issued: 2002
Voltammetric detection of vitamin B1 at carbon paste electrodes and its determination in tablets
- Oni, Joshua, Westbroek, Philippe, Nyokong, Tebello
- Authors: Oni, Joshua , Westbroek, Philippe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289678 , vital:56662 , xlink:href="https://doi.org/10.1002/1521-4109(200209)14"
- Description: The voltammetric behavior of vitamin B1 in alkaline medium at carbon paste electrode (CPE) is discussed. A method based on cyclic voltammetry for the determination of vitamin B1 at carbon paste electrode modified with manganese phthalocyanine (MnPc-CPE) is presented. In pH 10 buffer, the modified electrode showed catalytic activity towards the oxidation of vitamin B1 by considerably increasing the oxidation current of one of the observed waves compared to the oxidation current obtained at an unmodified electrode. The modified electrode was stable towards the determination of vitamin B1 compared to the unmodified electrode that is completely poisoned after a few scans. A linear relationship between the oxidation current and the concentration of vitamin B1 in solution was observed. The detection limit for vitamin B1 at the modified electrode was of the order of 10−5 mol dm−3. Commercial vitamin B1 tablets were analyzed using the modified electrodes.
- Full Text:
- Date Issued: 2002
- Authors: Oni, Joshua , Westbroek, Philippe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289678 , vital:56662 , xlink:href="https://doi.org/10.1002/1521-4109(200209)14"
- Description: The voltammetric behavior of vitamin B1 in alkaline medium at carbon paste electrode (CPE) is discussed. A method based on cyclic voltammetry for the determination of vitamin B1 at carbon paste electrode modified with manganese phthalocyanine (MnPc-CPE) is presented. In pH 10 buffer, the modified electrode showed catalytic activity towards the oxidation of vitamin B1 by considerably increasing the oxidation current of one of the observed waves compared to the oxidation current obtained at an unmodified electrode. The modified electrode was stable towards the determination of vitamin B1 compared to the unmodified electrode that is completely poisoned after a few scans. A linear relationship between the oxidation current and the concentration of vitamin B1 in solution was observed. The detection limit for vitamin B1 at the modified electrode was of the order of 10−5 mol dm−3. Commercial vitamin B1 tablets were analyzed using the modified electrodes.
- Full Text:
- Date Issued: 2002
Synthesis, electrochemical and photochemical properties of unsymmetrically substituted zinc phthalocyanine complexes
- Matlaba, Pulane M, Nyokong, Tebello
- Authors: Matlaba, Pulane M , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289650 , vital:56658 , xlink:href="https://doi.org/10.1016/S0277-5387(02)01226-3"
- Description: The synthesis of symmetrically and unsymmetrically substituted zinc phthalocyanine (ZnPc) derivatives are reported. The ZnPc derivatives are synthesized by ring expansion of subphthalocyanine complexes. Ring substitution is effected with tert-butyl phenol, naphthol and hydroxybenzoic acid. Comparison of the redox potentials for complexes substituted with varying numbers of tert-butyl phenol: 1 (complex 5), 2 (complex 6), 3 (complex 7), 6 (complex 8) and 8 (complex 9) shows that the complexes with the highest number of substituents are more difficult to oxidize and easier to reduce. All the reported complexes are relatively photostable, with photobleaching quantum yields of the order of 10−5. Singlet oxygen quantum yields for the complexes ranged from 0.22 to 0.68.
- Full Text:
- Date Issued: 2002
- Authors: Matlaba, Pulane M , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289650 , vital:56658 , xlink:href="https://doi.org/10.1016/S0277-5387(02)01226-3"
- Description: The synthesis of symmetrically and unsymmetrically substituted zinc phthalocyanine (ZnPc) derivatives are reported. The ZnPc derivatives are synthesized by ring expansion of subphthalocyanine complexes. Ring substitution is effected with tert-butyl phenol, naphthol and hydroxybenzoic acid. Comparison of the redox potentials for complexes substituted with varying numbers of tert-butyl phenol: 1 (complex 5), 2 (complex 6), 3 (complex 7), 6 (complex 8) and 8 (complex 9) shows that the complexes with the highest number of substituents are more difficult to oxidize and easier to reduce. All the reported complexes are relatively photostable, with photobleaching quantum yields of the order of 10−5. Singlet oxygen quantum yields for the complexes ranged from 0.22 to 0.68.
- Full Text:
- Date Issued: 2002
Interaction of sulfur dioxide and cyanide with cobalt (II) tetrasulfophthalocyanine in aqueous media
- Thamae, Mamothibe, Nyokong, Tebello
- Authors: Thamae, Mamothibe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289595 , vital:56652 , xlink:href="https://doi.org/10.1016/S0277-5387(01)00968-8"
- Description: Kinetic and equilibrium studies for the coordination of cyanide or sulfur dioxide to the cobalt(II) tetrasulfophthalocyanine ([CoTSPc]4−) complex are reported. The equilibrium constant for the coordination of the cyanide under pH 11 conditions and an oxygen atmosphere, and the formation of [(CN−)2Co(III)TSPc]5− species, was found to be 2.1×101 dm3 mol−1 and the rate constant, kf was found to be 7.4 dm3 mol−1 s−1. Similarly, the coordination of SO2 to [CoTSPc]4− occurred with an equilibrium constant of 8.7×101 dm3 mol−1 and a rate constant of 2.1×102 dm3 mol−1 s−1, at pH 11. These rate and equilibrium constants represent the coordination of the second cyanide or sulfur dioxide ligands to the [CoTSPc]4− species. Coordination of the first ligand occurred faster than that of the second ligand in both cases. The coordination is accompanied by the oxidation of the central Co(II) metal with the formation of a Co(III) tetrasulfophthalocyanine species.
- Full Text:
- Date Issued: 2002
Interaction of sulfur dioxide and cyanide with cobalt (II) tetrasulfophthalocyanine in aqueous media
- Authors: Thamae, Mamothibe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289595 , vital:56652 , xlink:href="https://doi.org/10.1016/S0277-5387(01)00968-8"
- Description: Kinetic and equilibrium studies for the coordination of cyanide or sulfur dioxide to the cobalt(II) tetrasulfophthalocyanine ([CoTSPc]4−) complex are reported. The equilibrium constant for the coordination of the cyanide under pH 11 conditions and an oxygen atmosphere, and the formation of [(CN−)2Co(III)TSPc]5− species, was found to be 2.1×101 dm3 mol−1 and the rate constant, kf was found to be 7.4 dm3 mol−1 s−1. Similarly, the coordination of SO2 to [CoTSPc]4− occurred with an equilibrium constant of 8.7×101 dm3 mol−1 and a rate constant of 2.1×102 dm3 mol−1 s−1, at pH 11. These rate and equilibrium constants represent the coordination of the second cyanide or sulfur dioxide ligands to the [CoTSPc]4− species. Coordination of the first ligand occurred faster than that of the second ligand in both cases. The coordination is accompanied by the oxidation of the central Co(II) metal with the formation of a Co(III) tetrasulfophthalocyanine species.
- Full Text:
- Date Issued: 2002
Maybe the courts are not such a Bleak House after all - or please sir, I want some more copyright
- Authors: Glover, Graham B
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70841 , vital:29749 , https://heinonline.org/HOL/P?h=hein.journals/soaf119&i=101
- Description: In our advanced technological age the law of copyright faces tremendous challenges. In particular, the Internet has created serious problems for those who wish to enforce their proprietary rights, and to protect their textual (and other) creations from unregulated and uninhibited reproduction.
- Full Text: false
- Date Issued: 2002
- Authors: Glover, Graham B
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70841 , vital:29749 , https://heinonline.org/HOL/P?h=hein.journals/soaf119&i=101
- Description: In our advanced technological age the law of copyright faces tremendous challenges. In particular, the Internet has created serious problems for those who wish to enforce their proprietary rights, and to protect their textual (and other) creations from unregulated and uninhibited reproduction.
- Full Text: false
- Date Issued: 2002
The advantages and disadvantages of long-term collective bargaining within the Metal & Engineering Industry and Mining Industry
- Labour Research Service (LRS)
- Authors: Labour Research Service (LRS)
- Date: 2002-11
- Subjects: Uncatalogued
- Language: English
- Type: book , text
- Identifier: http://hdl.handle.net/10962/60190 , vital:27745
- Description: This report highlights the advantages and disadvantages of long-term collective bargaining within the Metal & Engineering and Mining industries. It does not aim to set standards but to provide useful information on the experiences of negotiators bargaining for multi-year agreements. To this end a questionnaire was designed to draw commentary from various role-players within the abovementioned industries on the issue under investigation.
- Full Text:
- Date Issued: 2002-11
- Authors: Labour Research Service (LRS)
- Date: 2002-11
- Subjects: Uncatalogued
- Language: English
- Type: book , text
- Identifier: http://hdl.handle.net/10962/60190 , vital:27745
- Description: This report highlights the advantages and disadvantages of long-term collective bargaining within the Metal & Engineering and Mining industries. It does not aim to set standards but to provide useful information on the experiences of negotiators bargaining for multi-year agreements. To this end a questionnaire was designed to draw commentary from various role-players within the abovementioned industries on the issue under investigation.
- Full Text:
- Date Issued: 2002-11
Spectrophotometric and electrochemical studies of the interaction between iron (II) tetrasulfophthalocyanine and histamine
- Oni, Joshua, Nyokong, Tebello
- Authors: Oni, Joshua , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289629 , vital:56657 , xlink:href="https://doi.org/10.1142/S1088424602000233"
- Description: The interaction between iron(II) tetrasulfophthalocyanine ([FeIITSPc]4+) and histamine results in the oxidation of the central metal by oxygen in the former, with the formation of a complex denoted as [(His)FeIIITSPc]3− (where His = histamine). The rate constant for the formation of the complex is kf = 2.41 × 10−2dm3.mol−1.s−1 and an equilibrium constant of 6.3 dm3.mol-1 was obtained. The oxidation state of the central metal of [FeIITSPc]4− before and after the coordination of histamine is confirmed by spectroelectrochemistry. Further electrochemical oxidation of this [(His)FeIIITsPc]3− derivative results in a metal-based process proposed to involve an FeIV phthalocyanine species.
- Full Text:
- Date Issued: 2002
- Authors: Oni, Joshua , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289629 , vital:56657 , xlink:href="https://doi.org/10.1142/S1088424602000233"
- Description: The interaction between iron(II) tetrasulfophthalocyanine ([FeIITSPc]4+) and histamine results in the oxidation of the central metal by oxygen in the former, with the formation of a complex denoted as [(His)FeIIITSPc]3− (where His = histamine). The rate constant for the formation of the complex is kf = 2.41 × 10−2dm3.mol−1.s−1 and an equilibrium constant of 6.3 dm3.mol-1 was obtained. The oxidation state of the central metal of [FeIITSPc]4− before and after the coordination of histamine is confirmed by spectroelectrochemistry. Further electrochemical oxidation of this [(His)FeIIITsPc]3− derivative results in a metal-based process proposed to involve an FeIV phthalocyanine species.
- Full Text:
- Date Issued: 2002
Secretariate report - Mobilise and invest for a sustainable cadre development
- NUM
- Authors: NUM
- Date: 2002
- Subjects: NUM
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/149517 , vital:38860
- Description: Three years ago this Province under the banner of the Western Cape National Union of Mineworkers gathered in this constitutional structure, the Regional conference under the slogan “Develop Leadership to Advance Socialism”. That conference then declared and adopted a comprehensive programme of action to take forward that Regional conference declaration. That the regional committee should and within the broad framework of the declaration ensure that the NUM in a regional context fight for better working conditions of our members. That the RC develops concrete programmes for the broader structures and membership to understand and ultimately be implemented at those levels. This conference has to deal with the assessment of the progress made during this period under review. Within the context of contestation forward mobility is ensured that seeks to help build the working class leadership which is ultimately or essentially political leadership. Worker control is one of the key founding principles of our union which will be better understood and implemented when we are to begin to find synergy between the worker leadership and the intellectual capacity within our organisation. This report will deal with the different chapters as identified. This report will also deal with our participation in COSATU structures as well as lack of cohesiveness between branch leaders and general membership and also the possible fear to engage. We will also try and attempt to discuss the lack of information flow from our structures to the broader membership. As we engage this report, let us try to use our organisational tools to resolve the problems facing our region and in particular the branches and as a result find suitable solutions to build and strengthen the organisation.
- Full Text:
- Date Issued: 2002
- Authors: NUM
- Date: 2002
- Subjects: NUM
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/149517 , vital:38860
- Description: Three years ago this Province under the banner of the Western Cape National Union of Mineworkers gathered in this constitutional structure, the Regional conference under the slogan “Develop Leadership to Advance Socialism”. That conference then declared and adopted a comprehensive programme of action to take forward that Regional conference declaration. That the regional committee should and within the broad framework of the declaration ensure that the NUM in a regional context fight for better working conditions of our members. That the RC develops concrete programmes for the broader structures and membership to understand and ultimately be implemented at those levels. This conference has to deal with the assessment of the progress made during this period under review. Within the context of contestation forward mobility is ensured that seeks to help build the working class leadership which is ultimately or essentially political leadership. Worker control is one of the key founding principles of our union which will be better understood and implemented when we are to begin to find synergy between the worker leadership and the intellectual capacity within our organisation. This report will deal with the different chapters as identified. This report will also deal with our participation in COSATU structures as well as lack of cohesiveness between branch leaders and general membership and also the possible fear to engage. We will also try and attempt to discuss the lack of information flow from our structures to the broader membership. As we engage this report, let us try to use our organisational tools to resolve the problems facing our region and in particular the branches and as a result find suitable solutions to build and strengthen the organisation.
- Full Text:
- Date Issued: 2002
Cyclic voltammetric studies of octabutylthiophthalo-cyaninato-cobalt (II) and its self-assembled monolayer (SAM) on gold electrode
- Ozoemena, Kenneth, Westbroek, Philippe, Nyokong, Tebello
- Authors: Ozoemena, Kenneth , Westbroek, Philippe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289567 , vital:56650 , xlink:href="https://doi.org/10.1142/S1088424602000130"
- Description: The synthesis of thiol-derivatized cobalt phthalocyanine complex, 2,3,9,10,16,17,23,24-octa (butylthiophthalocyaninatocobalt(II) (CoOBTPc) is described. Cyclic voltammetric data of this complex in DMF showed five quasi-reversible and reversible, diffusion-controlled redox couples, comprising both the phthalocyanine ring and central metal redox processes. The CoOBTPc complex forms a self-assembled monolayer (SAM) on gold electrode. The investigation of the integrity of this SAM, using the established cyclic voltammetric methods in aqueous alkaline solutions, gave evidence about the formation of a stable and easily reproducible monolayer. However, due to its susceptibility to destruction via oxidative and reductive desorptions, its potential application as an electrochemical sensor in alkaline pH is limited to a potential window of between −0.20 and +0.55 V vs Ag/AgCl.
- Full Text:
- Date Issued: 2002
- Authors: Ozoemena, Kenneth , Westbroek, Philippe , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289567 , vital:56650 , xlink:href="https://doi.org/10.1142/S1088424602000130"
- Description: The synthesis of thiol-derivatized cobalt phthalocyanine complex, 2,3,9,10,16,17,23,24-octa (butylthiophthalocyaninatocobalt(II) (CoOBTPc) is described. Cyclic voltammetric data of this complex in DMF showed five quasi-reversible and reversible, diffusion-controlled redox couples, comprising both the phthalocyanine ring and central metal redox processes. The CoOBTPc complex forms a self-assembled monolayer (SAM) on gold electrode. The investigation of the integrity of this SAM, using the established cyclic voltammetric methods in aqueous alkaline solutions, gave evidence about the formation of a stable and easily reproducible monolayer. However, due to its susceptibility to destruction via oxidative and reductive desorptions, its potential application as an electrochemical sensor in alkaline pH is limited to a potential window of between −0.20 and +0.55 V vs Ag/AgCl.
- Full Text:
- Date Issued: 2002
A workers handbook on HIV and AIDS
- COSATU
- Authors: COSATU
- Date: 2002
- Subjects: COSATU
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/135270 , vital:37253
- Description: AIDS is a trade union issue and must be discussed and placed on the agendas of all union meetings. We have committed ourselves to campaign for HIV prevention, care and treatment with the same determination and energy with which we fight many other working class struggles. COSATU has also committed to work in partnership with other trade unions, government, business and organs of civil society in the fight against the disease.”
- Full Text:
- Date Issued: 2002
- Authors: COSATU
- Date: 2002
- Subjects: COSATU
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/135270 , vital:37253
- Description: AIDS is a trade union issue and must be discussed and placed on the agendas of all union meetings. We have committed ourselves to campaign for HIV prevention, care and treatment with the same determination and energy with which we fight many other working class struggles. COSATU has also committed to work in partnership with other trade unions, government, business and organs of civil society in the fight against the disease.”
- Full Text:
- Date Issued: 2002
Voltammetric characterization of the self-assembled monolayer (SAM) of octabutylthiophthalocyaninatoiron (II)
- Ozoemena,Kenneth, Nyokong, Tebello
- Authors: Ozoemena,Kenneth , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/290419 , vital:56748 , xlink:href="https://doi.org/10.1016/S0013-4686(02)00362-6"
- Description: The fabrication of a self-assembled monolayer (SAM) of 2,3,9,10,16,17,23,24-octa (butylthio)-phthalocyaninatoiron(II) [FePc(SBu)8] on gold electrode is described. The integrity of the SAM, with respect to its ability to block certain Faradaic processes, is interrogated using cyclic voltammetric experiments in aqueous solutions. The experiments show that this SAM provide an excellent blocking capability to the Faradaic processes emanating from gold surface oxidation, underpotential deposition (UPD) of copper and redox chemistry of Fe(NH4)(SO4)2 in HClO4. It is revealed by cyclic voltammetry that an ill-defined reversible couple of the SAM of FePc(SBu)8 can be greatly improved by a simple repetitive cycling of the modified electrode in a DMF solution containing TBAP within a short space of time (ca. 2 min). This ‘activation’ process provides good information concerning the surface coverage and orientation of the monolayer. The reversible redox wave shows a potential shift of about −57 mV per pH in the pH range of 2–9. A preliminary investigation indicates that FePc(SBu)8-SAM modified gold electrode shows electrocatalytic activity toward the oxidation of L-cysteine in acidic medium. The monolayer is stable and easily reproducible. However, due to its susceptibility to destruction via oxidative and reductive desorptions, its potential application as an electrochemical sensor would be much better in acidic and neutral than alkaline environments.
- Full Text:
- Date Issued: 2002
- Authors: Ozoemena,Kenneth , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/290419 , vital:56748 , xlink:href="https://doi.org/10.1016/S0013-4686(02)00362-6"
- Description: The fabrication of a self-assembled monolayer (SAM) of 2,3,9,10,16,17,23,24-octa (butylthio)-phthalocyaninatoiron(II) [FePc(SBu)8] on gold electrode is described. The integrity of the SAM, with respect to its ability to block certain Faradaic processes, is interrogated using cyclic voltammetric experiments in aqueous solutions. The experiments show that this SAM provide an excellent blocking capability to the Faradaic processes emanating from gold surface oxidation, underpotential deposition (UPD) of copper and redox chemistry of Fe(NH4)(SO4)2 in HClO4. It is revealed by cyclic voltammetry that an ill-defined reversible couple of the SAM of FePc(SBu)8 can be greatly improved by a simple repetitive cycling of the modified electrode in a DMF solution containing TBAP within a short space of time (ca. 2 min). This ‘activation’ process provides good information concerning the surface coverage and orientation of the monolayer. The reversible redox wave shows a potential shift of about −57 mV per pH in the pH range of 2–9. A preliminary investigation indicates that FePc(SBu)8-SAM modified gold electrode shows electrocatalytic activity toward the oxidation of L-cysteine in acidic medium. The monolayer is stable and easily reproducible. However, due to its susceptibility to destruction via oxidative and reductive desorptions, its potential application as an electrochemical sensor would be much better in acidic and neutral than alkaline environments.
- Full Text:
- Date Issued: 2002
Synthesis, photophysical and photochemical studies of germanium and tin phthalocyanine complexes
- Maree, Suzanne, Phillips, David, Nyokong, Tebello
- Authors: Maree, Suzanne , Phillips, David , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289667 , vital:56661 , xlink:href="https://doi.org/10.1142/S108842460200004X"
- Description: This work reports on the synthesis of tin and germanium phthalocyanine complexes containing phenoxy and substituted phenoxy groups as phthalocyanine ring substituents. The compounds studied are: dichlorogermanium phthalocyanine complexes containing eight phenoxy (4a), o-methyl phenoxy (4b) or estrone (4c) groups on the ring. The corresponding dichlorotin complexes (5a, 5b and 5c) and diiodotin complex (6a) were also investigated, as well as diestrone phthalocyaninato tin (7). Germanium octaphenoxy phthalocyanine complexes undergo phototransformation rather than direct photobleaching, whereas tin octaphenoxy phthalocyanine complexes undergo a photobleaching process, which is mediated by photoreduction of the phthalocyanine ring. Tin octaphenoxy phthalocyanine complexes gave higher ΦΔ values than the corresponding germanium complexes. Also tin phthalocyanine complexes containing an unsubstituted ring gave higher ΦΔ values than the corresponding octaphenoxy substituted complexes. The triplet quantum yields increased with the increase in electron-donating power of the ring substituents.
- Full Text:
- Date Issued: 2002
- Authors: Maree, Suzanne , Phillips, David , Nyokong, Tebello
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289667 , vital:56661 , xlink:href="https://doi.org/10.1142/S108842460200004X"
- Description: This work reports on the synthesis of tin and germanium phthalocyanine complexes containing phenoxy and substituted phenoxy groups as phthalocyanine ring substituents. The compounds studied are: dichlorogermanium phthalocyanine complexes containing eight phenoxy (4a), o-methyl phenoxy (4b) or estrone (4c) groups on the ring. The corresponding dichlorotin complexes (5a, 5b and 5c) and diiodotin complex (6a) were also investigated, as well as diestrone phthalocyaninato tin (7). Germanium octaphenoxy phthalocyanine complexes undergo phototransformation rather than direct photobleaching, whereas tin octaphenoxy phthalocyanine complexes undergo a photobleaching process, which is mediated by photoreduction of the phthalocyanine ring. Tin octaphenoxy phthalocyanine complexes gave higher ΦΔ values than the corresponding germanium complexes. Also tin phthalocyanine complexes containing an unsubstituted ring gave higher ΦΔ values than the corresponding octaphenoxy substituted complexes. The triplet quantum yields increased with the increase in electron-donating power of the ring substituents.
- Full Text:
- Date Issued: 2002
Rhodes University Graduation Ceremony 2002
- Authors: Rhodes University
- Date: 2002
- Language: English
- Type: text
- Identifier: vital:8145 , http://hdl.handle.net/10962/d1007267
- Description: Rhodes University Graduation Ceremonies 1820 Settlers National Monument Friday, 5 April 2002 at 10:30; 14:30 & 18:00 [and] Saturday, 6 April 2002 at 10:30 , Graduation Ceremony Christian Centre, Wyse Street, East London Friday, 10 May 2002 at 18:00
- Full Text:
- Date Issued: 2002
- Authors: Rhodes University
- Date: 2002
- Language: English
- Type: text
- Identifier: vital:8145 , http://hdl.handle.net/10962/d1007267
- Description: Rhodes University Graduation Ceremonies 1820 Settlers National Monument Friday, 5 April 2002 at 10:30; 14:30 & 18:00 [and] Saturday, 6 April 2002 at 10:30 , Graduation Ceremony Christian Centre, Wyse Street, East London Friday, 10 May 2002 at 18:00
- Full Text:
- Date Issued: 2002
Reporting indigenous knowledge: the choices they deserve the local is the global
- Authors: Boshoff, Priscilla A
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71176 , vital:29804 , http://doi:10.1006/jmbi.1995.0238
- Description: A few days ago, an interesting article dealing with community development and education came close to being published in a national newspaper. But the editor tossed it back at the surprised journalist, and told him to write it again. Here are some excerpts: Researchers here have recently been facilitating local people to rediscover traditional practices that have been lost through the processes of colonisation and changes in lifestyles. “We are very excited about the ways in which things are being discovered,” said Samuel Mann, research facilitator at the project. “People are beginning to reclaim some of the ways of knowing that still have meaning and relevance to modern everyday life. People are rediscovering the importance of Indigenous Knowledge.” Mba Ngcobo, one of the participants in the project, showed how he and other members of his community had built a grain pit using old traditional knowledge. “It works really well,” he said, “it is amazing how these old ways really work. Our ancestors had marvellous ways of doing things. We can really appreciate the skills that are slowly being lost to us.” Mann explained how the traditional pit storage method produced carbon dioxide that keeps the grain fresh and insect-free for months. “Carbon dioxide storage is now the preferred way of many milling and storage companies to keep grain. It keeps grain fresh without having to resort to insecticides.”
- Full Text:
- Date Issued: 2002
- Authors: Boshoff, Priscilla A
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71176 , vital:29804 , http://doi:10.1006/jmbi.1995.0238
- Description: A few days ago, an interesting article dealing with community development and education came close to being published in a national newspaper. But the editor tossed it back at the surprised journalist, and told him to write it again. Here are some excerpts: Researchers here have recently been facilitating local people to rediscover traditional practices that have been lost through the processes of colonisation and changes in lifestyles. “We are very excited about the ways in which things are being discovered,” said Samuel Mann, research facilitator at the project. “People are beginning to reclaim some of the ways of knowing that still have meaning and relevance to modern everyday life. People are rediscovering the importance of Indigenous Knowledge.” Mba Ngcobo, one of the participants in the project, showed how he and other members of his community had built a grain pit using old traditional knowledge. “It works really well,” he said, “it is amazing how these old ways really work. Our ancestors had marvellous ways of doing things. We can really appreciate the skills that are slowly being lost to us.” Mann explained how the traditional pit storage method produced carbon dioxide that keeps the grain fresh and insect-free for months. “Carbon dioxide storage is now the preferred way of many milling and storage companies to keep grain. It keeps grain fresh without having to resort to insecticides.”
- Full Text:
- Date Issued: 2002