Interaction of cyanide with iron (II) phthalocyanine
- Authors: Nyokong, Tebello
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295497 , vital:57347 , xlink:href="https://doi.org/10.1039/DT9930003601"
- Description: The kinetics and equilibria for the reaction between cyanide and iron (II) phthalocyanine [Fe(pc)](H2pc = phthalocyanine) in dimethyl sulfoxide (dmso) were studied at 25 °C. The complex [Fe(pc)(CN)2]2– is formed in two consecutive pseudo-first-order processes with k2f= 17.5 ± 0.8 dm3 mol–1 s–1 and k3f= 0.20 ± 0.05 dm3 mol–1 s–1, where k2f and k3f are the rate constants for the binding of the first and second cyanide ligands, respectively. The equilbrium constants were fund to be K2= 3.0 × 103 dm3 mol–1 and K3= 5.7 × 102 dm3 mol–1, for the formation of [Fe(pc)(CN)(dmso)]– and [Fe(pc)(CN)2]2–, respectively.
- Full Text:
- Date Issued: 1993
- Authors: Nyokong, Tebello
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295497 , vital:57347 , xlink:href="https://doi.org/10.1039/DT9930003601"
- Description: The kinetics and equilibria for the reaction between cyanide and iron (II) phthalocyanine [Fe(pc)](H2pc = phthalocyanine) in dimethyl sulfoxide (dmso) were studied at 25 °C. The complex [Fe(pc)(CN)2]2– is formed in two consecutive pseudo-first-order processes with k2f= 17.5 ± 0.8 dm3 mol–1 s–1 and k3f= 0.20 ± 0.05 dm3 mol–1 s–1, where k2f and k3f are the rate constants for the binding of the first and second cyanide ligands, respectively. The equilbrium constants were fund to be K2= 3.0 × 103 dm3 mol–1 and K3= 5.7 × 102 dm3 mol–1, for the formation of [Fe(pc)(CN)(dmso)]– and [Fe(pc)(CN)2]2–, respectively.
- Full Text:
- Date Issued: 1993
Kinetics of the reaction of cyanide with ruthenium phthalocyanine complexes
- Nyokong, Tebello, Guthrie-Strachan, Jeffry
- Authors: Nyokong, Tebello , Guthrie-Strachan, Jeffry
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295509 , vital:57348 , xlink:href="https://doi.org/10.1016/S0020-1693(00)85128-2"
- Description: Kinetic studies of the reaction of cyanide with (CO)(DMF)RuPc and (DMSO)2RuPc in DMF are reported. In the presence of a large excess of cyanide, the (CN)2RuPc complex is formed by pseudo first order kinetics. The reaction is first order in both cyanide and phthalocyanine, with specific rate constants of 5.2×10−2 and 7.2×10−2 M−1 s−1 for reactions of cyanide with (CO)(DMF)RuPc and (DMSO)2RuPc, respectively. The rate constants correspond to the coordination of the second cyanide ligand to the ruthenium phthalocyanine species.
- Full Text:
- Date Issued: 1993
- Authors: Nyokong, Tebello , Guthrie-Strachan, Jeffry
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295509 , vital:57348 , xlink:href="https://doi.org/10.1016/S0020-1693(00)85128-2"
- Description: Kinetic studies of the reaction of cyanide with (CO)(DMF)RuPc and (DMSO)2RuPc in DMF are reported. In the presence of a large excess of cyanide, the (CN)2RuPc complex is formed by pseudo first order kinetics. The reaction is first order in both cyanide and phthalocyanine, with specific rate constants of 5.2×10−2 and 7.2×10−2 M−1 s−1 for reactions of cyanide with (CO)(DMF)RuPc and (DMSO)2RuPc, respectively. The rate constants correspond to the coordination of the second cyanide ligand to the ruthenium phthalocyanine species.
- Full Text:
- Date Issued: 1993
The nature of the oxidation products of dicyanoruthenium phthalocyanine in aqueous and non-aqueous solvents
- Authors: Nyokong, Tebello
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295543 , vital:57352 , xlink:href="https://doi.org/10.1016/S0277-5387(00)81741-6"
- Description: The cyclic voltammetry of [(CN)2RuIIPc]2− in acetonitrile or dichloromethane shows two oxidation couples at E12 = 0.31 and 0.85 V (vs S.C.E.) in CH2Cl2 and E12 = 0.45 and 1.15 V (vs S.C.E.) in acetonitrile. The spectroelectrochemistry of [(CN)2RuIIPc]2− in these solvents showed that oxidations occur at the phthalocyanine ligand. K2[(CN)2RuIIPc] dissolves in water at pHs greater than 5. The cyclic voltammetry of this complex showed oxidation couples at 0.32 and 0.29 V (vs S.C.E.) for aqueous solutions containing sodium sulphate (0.1M) and for buffered solutions (pH = 9), respectively. Both cyclic voltammetry and controlled potential coulometry gave evidence of electrocrystallization of the oxidation product. Chemical oxidations of [(CN)2RuIIPc]2− in water also showed phthalocyanine ligand oxidation.
- Full Text:
- Date Issued: 1993
- Authors: Nyokong, Tebello
- Date: 1993
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295543 , vital:57352 , xlink:href="https://doi.org/10.1016/S0277-5387(00)81741-6"
- Description: The cyclic voltammetry of [(CN)2RuIIPc]2− in acetonitrile or dichloromethane shows two oxidation couples at E12 = 0.31 and 0.85 V (vs S.C.E.) in CH2Cl2 and E12 = 0.45 and 1.15 V (vs S.C.E.) in acetonitrile. The spectroelectrochemistry of [(CN)2RuIIPc]2− in these solvents showed that oxidations occur at the phthalocyanine ligand. K2[(CN)2RuIIPc] dissolves in water at pHs greater than 5. The cyclic voltammetry of this complex showed oxidation couples at 0.32 and 0.29 V (vs S.C.E.) for aqueous solutions containing sodium sulphate (0.1M) and for buffered solutions (pH = 9), respectively. Both cyclic voltammetry and controlled potential coulometry gave evidence of electrocrystallization of the oxidation product. Chemical oxidations of [(CN)2RuIIPc]2− in water also showed phthalocyanine ligand oxidation.
- Full Text:
- Date Issued: 1993
Cyclic voltammetry and photooxidation of molybdenum (V) phthalocyanine
- Authors: Nyokong, Tebello
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295475 , vital:57344 , xlink:href="https://doi.org/10.1016/S0277-5387(00)86594-8"
- Description: Cyclic voltammetry of OMoV(OH)Pc in chloronaphthalene shows two quasi-reversible oxidation couples at 0.38 and 1.22 V and three quasi-reversible reduction couples at −0.74, −1.15 and −1.85 V vs S.C.E. Bulk electrolysis of OMoV(OH)Pc (Pc2 = phthalocyanine dianion) shows that the first oxidation couple is due to the oxidation of the central MoV metal to MoVI and the first reduction couple due to reduction to OMoIVPc. Cyclic voltammetry and spectroelectrochemistry in DMSO also showed redox activity at the metal. Further reductions or oxidations in OMoVPc complexes occur at the phthalocyanine ring. OMoV(OH)Pc is readily photooxidized at the metal in the presence dichloromethane or dichlorobenzene, with the formation of OMoVIPc species.
- Full Text:
- Date Issued: 1994
- Authors: Nyokong, Tebello
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295475 , vital:57344 , xlink:href="https://doi.org/10.1016/S0277-5387(00)86594-8"
- Description: Cyclic voltammetry of OMoV(OH)Pc in chloronaphthalene shows two quasi-reversible oxidation couples at 0.38 and 1.22 V and three quasi-reversible reduction couples at −0.74, −1.15 and −1.85 V vs S.C.E. Bulk electrolysis of OMoV(OH)Pc (Pc2 = phthalocyanine dianion) shows that the first oxidation couple is due to the oxidation of the central MoV metal to MoVI and the first reduction couple due to reduction to OMoIVPc. Cyclic voltammetry and spectroelectrochemistry in DMSO also showed redox activity at the metal. Further reductions or oxidations in OMoVPc complexes occur at the phthalocyanine ring. OMoV(OH)Pc is readily photooxidized at the metal in the presence dichloromethane or dichlorobenzene, with the formation of OMoVIPc species.
- Full Text:
- Date Issued: 1994
Cyclic voltammetry and spectroelectrochemistry of rhodium phthalocyanines
- Authors: Nyokong, Tebello
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295486 , vital:57346 , xlink:href="https://doi.org/10.1039/DT9940001359"
- Description: The electrochemistry of RhIII(pc)(pc = phthalocyanine dianion) complexes containing chloride, pyridine, dimethyl sulfoxide (dmso) and cyanide as axial ligands was investigated by cyclic voltammetry and UV/VIS spectroelectrochemistry. The compounds were K[Rh(pc)(CN)2], [Rh(pc)(Cl)(py)] and [Rh(pc)Cl(dmso)]. For all of these the first oxidation occurs at the phthalocyanine ligand with the formation of a π-cation radical species. The addition of one electron to the complexes leads to one of two different reduction products depending on the nature of the axial ligands. The first reduction of [Rh(pc)Cl(py)] and [Rh(pc)Cl(dmso)] occurs at the metal, followed by rapid dimerization of the reduced species. The first and subsequent reductions of K[Rh(pc)(CN)2] occur at the ring.
- Full Text:
- Date Issued: 1994
- Authors: Nyokong, Tebello
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295486 , vital:57346 , xlink:href="https://doi.org/10.1039/DT9940001359"
- Description: The electrochemistry of RhIII(pc)(pc = phthalocyanine dianion) complexes containing chloride, pyridine, dimethyl sulfoxide (dmso) and cyanide as axial ligands was investigated by cyclic voltammetry and UV/VIS spectroelectrochemistry. The compounds were K[Rh(pc)(CN)2], [Rh(pc)(Cl)(py)] and [Rh(pc)Cl(dmso)]. For all of these the first oxidation occurs at the phthalocyanine ligand with the formation of a π-cation radical species. The addition of one electron to the complexes leads to one of two different reduction products depending on the nature of the axial ligands. The first reduction of [Rh(pc)Cl(py)] and [Rh(pc)Cl(dmso)] occurs at the metal, followed by rapid dimerization of the reduced species. The first and subsequent reductions of K[Rh(pc)(CN)2] occur at the ring.
- Full Text:
- Date Issued: 1994
Photoassisted electron transfer between sulfur dioxide and tin (IV) phthalocyanines
- Authors: Nyokong, Tebello
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295520 , vital:57349 , xlink:href="https://doi.org/10.1039/C39940001983"
- Description: Photolysis of tin(IV) phthalocyanine complexes in the presence of sulfur dioxide shows a first-order kinetic dependence on sulfur dioxide, and a one-electron reduction of SnPc to an anion radical species.
- Full Text:
- Date Issued: 1994
- Authors: Nyokong, Tebello
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295520 , vital:57349 , xlink:href="https://doi.org/10.1039/C39940001983"
- Description: Photolysis of tin(IV) phthalocyanine complexes in the presence of sulfur dioxide shows a first-order kinetic dependence on sulfur dioxide, and a one-electron reduction of SnPc to an anion radical species.
- Full Text:
- Date Issued: 1994
Photoreduction of tin (IV) phthalocyanines
- Authors: Nyokong, Tebello
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293413 , vital:57083 , xlink:href="https://doi.org/10.1016/S0277-5387(00)83491-9"
- Description: Photolysis of Sn(IV)Pc(OH)2 (Pc = phthalocyanine dianion) and Sn(IV)Pc(Cl)2 using a tungsten lamp, and in the presence of SnCl2·2H2O as an electron donor results in the reduction of these complexes of π anion radical species. The reduction shows second order dependence on the concentration of the Sn(IV)Pc complexes and a first order dependence on SnCl2·H2O.
- Full Text:
- Date Issued: 1994
- Authors: Nyokong, Tebello
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293413 , vital:57083 , xlink:href="https://doi.org/10.1016/S0277-5387(00)83491-9"
- Description: Photolysis of Sn(IV)Pc(OH)2 (Pc = phthalocyanine dianion) and Sn(IV)Pc(Cl)2 using a tungsten lamp, and in the presence of SnCl2·2H2O as an electron donor results in the reduction of these complexes of π anion radical species. The reduction shows second order dependence on the concentration of the Sn(IV)Pc complexes and a first order dependence on SnCl2·H2O.
- Full Text:
- Date Issued: 1994
Redox reactions of an Mo (V) tetrasulfophthalocyanine
- Ferraudi, Guillermo, Nyokong, Tebello, Feliz, Mario, Perkovic, Marc, Rillema, D Paul
- Authors: Ferraudi, Guillermo , Nyokong, Tebello , Feliz, Mario , Perkovic, Marc , Rillema, D Paul
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295530 , vital:57351 , xlink:href="https://doi.org/10.1016/0020-1693(93)03664-V"
- Description: The preparation of an Mo(V) tetrasulfophthalocyanine and some of its thermal and photochemical reactions have been investigated in this work. Electrochemical processes have been followed by means of the UVVis spectral changes and compared with those observed in flash photolysis. Mo(IV) and Mo(V)-ligand-radical species are common intermediates of the electrochemical and photochemical reactions. In 254 nm irradiations of the Mo(V) tetrasulfophthalocyanine in aqueous solutions of 2-propanol, the macrocycle can be photohydrogenated and the product of the photolysis can be reoxidized with O2 back to the parent complex.
- Full Text:
- Date Issued: 1994
- Authors: Ferraudi, Guillermo , Nyokong, Tebello , Feliz, Mario , Perkovic, Marc , Rillema, D Paul
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/295530 , vital:57351 , xlink:href="https://doi.org/10.1016/0020-1693(93)03664-V"
- Description: The preparation of an Mo(V) tetrasulfophthalocyanine and some of its thermal and photochemical reactions have been investigated in this work. Electrochemical processes have been followed by means of the UVVis spectral changes and compared with those observed in flash photolysis. Mo(IV) and Mo(V)-ligand-radical species are common intermediates of the electrochemical and photochemical reactions. In 254 nm irradiations of the Mo(V) tetrasulfophthalocyanine in aqueous solutions of 2-propanol, the macrocycle can be photohydrogenated and the product of the photolysis can be reoxidized with O2 back to the parent complex.
- Full Text:
- Date Issued: 1994
Equilibrium and kinetic studies of the reaction between pyridine and cobalt (II) phthalocyanine in DMSO
- Authors: Nyokong, Tebello
- Date: 1995
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293380 , vital:57080 , xlink:href="https://doi.org/10.1016/0277-5387(95)00090-F"
- Description: Kinetics and equilibria for the reaction between pyridine and cobalt(II) phthalocyanine [CoPc] (H2Pc = phthalocyanine) in dimethyl sulphoxide (DMSO) were studied at 25°C. The complex, CoPc(py)2, is formed in two consecutive steps. The formation of the mono-substituted CoPc(py)(DMSO) occurs first with a pseudo-first-order rate constant of k1f = 7.7 ± 0.3 × 10−3 dm3 mol−1 s−1. The final disubstituted CoPc(py)2 complex is formed with k2f= 1.1 ± 0.1 × 10−4dm3mol−1−1. The equilibrium constants were found to be K1 = 160 ± 20dm3 mol−1 and K2 = 15 ± 3 dm3mol−1 for the formation of CoPc(py)(DMSO) and CoPc(py)2, respectively.
- Full Text:
- Date Issued: 1995
- Authors: Nyokong, Tebello
- Date: 1995
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293380 , vital:57080 , xlink:href="https://doi.org/10.1016/0277-5387(95)00090-F"
- Description: Kinetics and equilibria for the reaction between pyridine and cobalt(II) phthalocyanine [CoPc] (H2Pc = phthalocyanine) in dimethyl sulphoxide (DMSO) were studied at 25°C. The complex, CoPc(py)2, is formed in two consecutive steps. The formation of the mono-substituted CoPc(py)(DMSO) occurs first with a pseudo-first-order rate constant of k1f = 7.7 ± 0.3 × 10−3 dm3 mol−1 s−1. The final disubstituted CoPc(py)2 complex is formed with k2f= 1.1 ± 0.1 × 10−4dm3mol−1−1. The equilibrium constants were found to be K1 = 160 ± 20dm3 mol−1 and K2 = 15 ± 3 dm3mol−1 for the formation of CoPc(py)(DMSO) and CoPc(py)2, respectively.
- Full Text:
- Date Issued: 1995
The reaction of cyanide with iron (II) hexadecachlorophthalocyanine
- Authors: Nyokong, Tebello
- Date: 1995
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293447 , vital:57086 , xlink:href="https://doi.org/10.1016/0277-5387(94)00291-L"
- Description: Kinetics and equilibria for the reaction between cyanide and iron(II) hexadecachlorophthalocyanine ((Cl)16PcFe(DMSO)2, where Pc(−2) = phthalocyanine dianion) in dimethyl sulphoxide (DMSO) are reported. Only the spectrophotometric changes due to the formation of the dicyano, [(Cl)16PcFe(CN)2]2−, complex were observed. This complex is formed with the equilibrium constant, K3 = 1.6 × 103 dm3 mol−1 and a rate constant of k3f = 4.2 × 10−3 dm3 mol−1 s−1. The K2[(Cl)16PcFe(CN)2] complex dissolves in DMSO and dimethyl formamide (DMF) with ϵ = 110 000 and 92 000 dm3 mol−1 cm−1, respectively.
- Full Text:
- Date Issued: 1995
- Authors: Nyokong, Tebello
- Date: 1995
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293447 , vital:57086 , xlink:href="https://doi.org/10.1016/0277-5387(94)00291-L"
- Description: Kinetics and equilibria for the reaction between cyanide and iron(II) hexadecachlorophthalocyanine ((Cl)16PcFe(DMSO)2, where Pc(−2) = phthalocyanine dianion) in dimethyl sulphoxide (DMSO) are reported. Only the spectrophotometric changes due to the formation of the dicyano, [(Cl)16PcFe(CN)2]2−, complex were observed. This complex is formed with the equilibrium constant, K3 = 1.6 × 103 dm3 mol−1 and a rate constant of k3f = 4.2 × 10−3 dm3 mol−1 s−1. The K2[(Cl)16PcFe(CN)2] complex dissolves in DMSO and dimethyl formamide (DMF) with ϵ = 110 000 and 92 000 dm3 mol−1 cm−1, respectively.
- Full Text:
- Date Issued: 1995
Cyclic voltammetry and spectroelectrochemistry of osmium phthalocyanines in aqueous and non-aqueous solvents
- Sekota, Mantoa, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 1996
- 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.
- Full Text:
- Date Issued: 1996
Electrocatalytic oxidation of cysteine by molybdenum (V) phthalocyanine complexes
- Mafatle, Tsukutlane J, Nyokong, Tebello
- Authors: Mafatle, Tsukutlane J , Nyokong, Tebello
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293369 , vital:57079 , xlink:href="https://doi.org/10.1016/0022-0728(95)04519-8"
- Description: Chemically modified electrodes, constructed by incorporating oxomolybdenum(V) phthalocyanine (OMo(V)(OH)Pc, Pc = phthalocyanine dianion) into graphite powder were used to catalyse the oxidation of cysteine. Solution catalysis of cysteine by oxomolybdenum(V) tetrasulfophthalocyanine, [OMo(V)(OH)TSPc]4−, was also investigated. A considerable reduction in overpotential for cysteine oxidation was observed. Cysteine oxidation occurred at 0.26 and 0.28 V vs. Ag/vbAgCl for catalysis by Omo(V)(OH)Pc and [OMo(V)(OH)TSPc]4− respectively as opposed to 0.77 V vs. Ag/vbAgCl observed on CoPc chemically modified electrodes. The anodic peak currents vary linearly with cysteine concentration in the range 0.02 to 0.08 mol dm−3 and 0.008 to 0.02 mol dm−3 for [OMo(V)(OH)TSPc]4− and OMo(V)Pc respectively.
- Full Text:
- Date Issued: 1996
- Authors: Mafatle, Tsukutlane J , Nyokong, Tebello
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293369 , vital:57079 , xlink:href="https://doi.org/10.1016/0022-0728(95)04519-8"
- Description: Chemically modified electrodes, constructed by incorporating oxomolybdenum(V) phthalocyanine (OMo(V)(OH)Pc, Pc = phthalocyanine dianion) into graphite powder were used to catalyse the oxidation of cysteine. Solution catalysis of cysteine by oxomolybdenum(V) tetrasulfophthalocyanine, [OMo(V)(OH)TSPc]4−, was also investigated. A considerable reduction in overpotential for cysteine oxidation was observed. Cysteine oxidation occurred at 0.26 and 0.28 V vs. Ag/vbAgCl for catalysis by Omo(V)(OH)Pc and [OMo(V)(OH)TSPc]4− respectively as opposed to 0.77 V vs. Ag/vbAgCl observed on CoPc chemically modified electrodes. The anodic peak currents vary linearly with cysteine concentration in the range 0.02 to 0.08 mol dm−3 and 0.008 to 0.02 mol dm−3 for [OMo(V)(OH)TSPc]4− and OMo(V)Pc respectively.
- Full Text:
- Date Issued: 1996
Perceptions of affirmative action
- Scott, Judith, Amos, Trevor L, Richard Scott, W
- Authors: Scott, Judith , Amos, Trevor L , Richard Scott, W
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270914 , vital:54491 , xlink:href="https://hdl.handle.net/10520/EJC-67e7bffd2"
- Description: Private and public South African employers have instituted affirmative action policies meant to provide employment opportunities to Black South Africans. A body of literature suggests that because of affirmative action policies Black hopes have been raised while Whites view such policies as having a negative impact on their opportunities. However, no extant literature details an empirical investigation of these suggestions. Therefore, this study focusses on the affirmative action perceptions held by 350 South African university commerce students.
- Full Text:
- Date Issued: 1996
- Authors: Scott, Judith , Amos, Trevor L , Richard Scott, W
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270914 , vital:54491 , xlink:href="https://hdl.handle.net/10520/EJC-67e7bffd2"
- Description: Private and public South African employers have instituted affirmative action policies meant to provide employment opportunities to Black South Africans. A body of literature suggests that because of affirmative action policies Black hopes have been raised while Whites view such policies as having a negative impact on their opportunities. However, no extant literature details an empirical investigation of these suggestions. Therefore, this study focusses on the affirmative action perceptions held by 350 South African university commerce students.
- Full Text:
- Date Issued: 1996
Pharmacokinetics of cyclizine following intravenous administration to human volunteers
- Kanfer, Isadore, Walker, Roderick B
- Authors: Kanfer, Isadore , Walker, Roderick B
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184389 , vital:44214 , xlink:href="https://doi.org/10.1016/0928-0987(96)00177-7"
- Description: The pharmacokinetics of cyclizine, a piperazine derivative useful in the prevention and treatment of nausea and vomiting, was investigated in six healthy male volunteers following an intravenous bolus dose. The drug is extensively distributed with a mean volume of distribution of 16.50 ± 3.33 l/kg and a mean total clearance of 0.870 ± 0.105 l/h per kg. Urinary excretion data showed that less than one percent of the dose was excreted up to 36 h as unchanged drug in the urine. The extremely low mean renal clearance (0.005 ± 0.002 l/h per kg) for the parent drug comprised only a small proportion of total clearance indicating that urinary excretion of parent drug is not a major route of elimination for cyclizine. The drug appears to exhibit biexponential pharmacokinetics and has a terminal elimination half-life of approximately 13 h.
- Full Text:
- Date Issued: 1996
- Authors: Kanfer, Isadore , Walker, Roderick B
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184389 , vital:44214 , xlink:href="https://doi.org/10.1016/0928-0987(96)00177-7"
- Description: The pharmacokinetics of cyclizine, a piperazine derivative useful in the prevention and treatment of nausea and vomiting, was investigated in six healthy male volunteers following an intravenous bolus dose. The drug is extensively distributed with a mean volume of distribution of 16.50 ± 3.33 l/kg and a mean total clearance of 0.870 ± 0.105 l/h per kg. Urinary excretion data showed that less than one percent of the dose was excreted up to 36 h as unchanged drug in the urine. The extremely low mean renal clearance (0.005 ± 0.002 l/h per kg) for the parent drug comprised only a small proportion of total clearance indicating that urinary excretion of parent drug is not a major route of elimination for cyclizine. The drug appears to exhibit biexponential pharmacokinetics and has a terminal elimination half-life of approximately 13 h.
- Full Text:
- Date Issued: 1996
Photochemically induced electron transfer between sulfur dioxide and tin (IV) mono-and di-phthalocyanines
- Nensala, Ngudiankama, Nzimande, Ayanda, Nyokong, Tebello
- Authors: Nensala, Ngudiankama , Nzimande, Ayanda , Nyokong, Tebello
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293402 , vital:57082 , xlink:href="https://doi.org/10.1016/1010-6030(96)04344-4"
- Description: Photolysis, using radiation from a tungsten lamp, of tin diphthalocyanine (Pc2Sn(IV)) in dichloromethane containing SO2 results in the one-electron oxidation of this species to [Pc(−2)Sn(IV)Pc(−1)]+. The relative quantum yields for the formation of the oxidized species were in the order of 10−3. The one-electron oxidized complex was also formed when Pc2Sn was photolysed in an acetonitrile/dichloromethane solvent mixture. Photolysis of the monomeric (L)2Sn(IV)Pc(LOH−, Cl−, Br− and F−) in pyridine and in the presence of SO2 resulted in the reduction of these species to (L)2Sn(IV)Pc(−3)]− with quantum yields in the order of 10−2.
- Full Text:
- Date Issued: 1996
- Authors: Nensala, Ngudiankama , Nzimande, Ayanda , Nyokong, Tebello
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293402 , vital:57082 , xlink:href="https://doi.org/10.1016/1010-6030(96)04344-4"
- Description: Photolysis, using radiation from a tungsten lamp, of tin diphthalocyanine (Pc2Sn(IV)) in dichloromethane containing SO2 results in the one-electron oxidation of this species to [Pc(−2)Sn(IV)Pc(−1)]+. The relative quantum yields for the formation of the oxidized species were in the order of 10−3. The one-electron oxidized complex was also formed when Pc2Sn was photolysed in an acetonitrile/dichloromethane solvent mixture. Photolysis of the monomeric (L)2Sn(IV)Pc(LOH−, Cl−, Br− and F−) in pyridine and in the presence of SO2 resulted in the reduction of these species to (L)2Sn(IV)Pc(−3)]− with quantum yields in the order of 10−2.
- Full Text:
- Date Issued: 1996
Spectroelectrochemical studies of tin (IV) diphthalocyanine
- Nensala, Ngudiankama, Nyokong, Tebello
- Authors: Nensala, Ngudiankama , Nyokong, Tebello
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293436 , vital:57085 , xlink:href="https://doi.org/10.1016/0277-5387(95)00325-1"
- Description: Cyclic voltammetry of tin(IV) diphthalocyanine (Pc2Sn) in dichloromethane containing TEAP shows two reduction couples at −0.56 and −0.89 versus saturated calomel electrode (SCE) and one oxidation couple at 0.35 V versus SCE; all were quasireversible one-electron couples. The oxidation couple corresponds to [Pc(−1)SnIVPc(−2)+/Pc(−2)SnIVPc(−2) and the reduction couples to Pc(−2)SnIVPc(−2)/[Pc(−3)SnIVPc(−2)]− and [Pc(−3)SnIVPc(−2)]−/[Pc(−3)SnIVPc(−3)]2−, respectively. The electronic absorption spectra of the various reduced or oxidized tin(IV) diphthalocyanine species are reported.
- Full Text:
- Date Issued: 1996
- Authors: Nensala, Ngudiankama , Nyokong, Tebello
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293436 , vital:57085 , xlink:href="https://doi.org/10.1016/0277-5387(95)00325-1"
- Description: Cyclic voltammetry of tin(IV) diphthalocyanine (Pc2Sn) in dichloromethane containing TEAP shows two reduction couples at −0.56 and −0.89 versus saturated calomel electrode (SCE) and one oxidation couple at 0.35 V versus SCE; all were quasireversible one-electron couples. The oxidation couple corresponds to [Pc(−1)SnIVPc(−2)+/Pc(−2)SnIVPc(−2) and the reduction couples to Pc(−2)SnIVPc(−2)/[Pc(−3)SnIVPc(−2)]− and [Pc(−3)SnIVPc(−2)]−/[Pc(−3)SnIVPc(−3)]2−, respectively. The electronic absorption spectra of the various reduced or oxidized tin(IV) diphthalocyanine species are reported.
- Full Text:
- Date Issued: 1996
Suppositories: An underutilized dosage form
- Webster, Jessica A, Dowse, Roslind, Walker, Roderick B
- Authors: Webster, Jessica A , Dowse, Roslind , Walker, Roderick B
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184697 , vital:44264 , xlink:href="https://hdl.handle.net/10520/AJA16836707_911"
- Description: The rectal route is useful for the delivery of both local acting and systemic drugs. In certain cases suppositories are the best form of therapy, or else they are an effective alternative when oral therapy is not possible. However; doctors rarely prescribe them and patients are often reluctant to use them. Understanding how suppositories work, and their numerous uses, can overcome the aversion to this particular dosage form. Pharmacists are in an ideal position to educate doctors, other health care providers, and patients, on the benefits of using suppositories and their correct use, and to offer advice on any problems associated with their use.
- Full Text:
- Date Issued: 1996
- Authors: Webster, Jessica A , Dowse, Roslind , Walker, Roderick B
- Date: 1996
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184697 , vital:44264 , xlink:href="https://hdl.handle.net/10520/AJA16836707_911"
- Description: The rectal route is useful for the delivery of both local acting and systemic drugs. In certain cases suppositories are the best form of therapy, or else they are an effective alternative when oral therapy is not possible. However; doctors rarely prescribe them and patients are often reluctant to use them. Understanding how suppositories work, and their numerous uses, can overcome the aversion to this particular dosage form. Pharmacists are in an ideal position to educate doctors, other health care providers, and patients, on the benefits of using suppositories and their correct use, and to offer advice on any problems associated with their use.
- Full Text:
- Date Issued: 1996
Catalytic behavior of osmium (II), rhodium (III) and ruthenium (II) Phthalocyanines towards the electrooxidation of cysteine on glassy carbon electrodes
- Sekota, Mantoa, Nyokong, Tebello
- 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.
- Full Text:
- Date Issued: 1997
- 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.
- Full Text:
- Date Issued: 1997
First-row transition metal phthalocyanines as catalysts for water electrolysis
- Chebotareva, Natalia, Nyokong, Tebello
- Authors: Chebotareva, Natalia , Nyokong, Tebello
- Date: 1997
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293391 , vital:57081 , xlink:href="https://doi.org/10.1016/S0013-4686(97)00033-9"
- Description: Modification of carbon electrodes with first row transition metal phthalocyanines results in the lowering of the potentials needed for water electrolysis in basic media, by 600 to 700 mV when compared to unmodified carbon electrodes. Nickel(II), cobalt(II) and iron(II) phthalocyanines show higher catalytic activity than zinc(II), manganese(II), copper(II) and metal free phthalocyanines.
- Full Text:
- Date Issued: 1997
- Authors: Chebotareva, Natalia , Nyokong, Tebello
- Date: 1997
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293391 , vital:57081 , xlink:href="https://doi.org/10.1016/S0013-4686(97)00033-9"
- Description: Modification of carbon electrodes with first row transition metal phthalocyanines results in the lowering of the potentials needed for water electrolysis in basic media, by 600 to 700 mV when compared to unmodified carbon electrodes. Nickel(II), cobalt(II) and iron(II) phthalocyanines show higher catalytic activity than zinc(II), manganese(II), copper(II) and metal free phthalocyanines.
- Full Text:
- Date Issued: 1997
Management education and training
- Authors: Amos, Trevor L , Quinn, Lynn
- Date: 1997
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270902 , vital:54490 , xlink:href="https://hdl.handle.net/10520/AJA10113487_559"
- Description: The paper outlines the role of language in leaming and cognitive development and argues that management education and training needs to be integrated with language development to enable students to cope with the demands made of them at university as well as with those of careers in the business world. An integrated language developmEint project developed by the Depanment of Management and academic language practitioners at Rhodes Uhlvetsity is descriptionbed and suggestions are outlined as to how university Management departments can integrate language development in their mainstream teaching.
- Full Text:
- Date Issued: 1997
- Authors: Amos, Trevor L , Quinn, Lynn
- Date: 1997
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270902 , vital:54490 , xlink:href="https://hdl.handle.net/10520/AJA10113487_559"
- Description: The paper outlines the role of language in leaming and cognitive development and argues that management education and training needs to be integrated with language development to enable students to cope with the demands made of them at university as well as with those of careers in the business world. An integrated language developmEint project developed by the Depanment of Management and academic language practitioners at Rhodes Uhlvetsity is descriptionbed and suggestions are outlined as to how university Management departments can integrate language development in their mainstream teaching.
- Full Text:
- Date Issued: 1997