Electrochemical studies of titanium, manganese and cobalt phthalocyanines
- Authors: Nombona, Nolwazi
- Date: 2009
- Subjects: Titanium , Manganese , Cobalt , Phthalocyanines , Electrochemistry , Electrodes , Self-assembly (Chemistry)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4312 , http://hdl.handle.net/10962/d1004970 , Titanium , Manganese , Cobalt , Phthalocyanines , Electrochemistry , Electrodes , Self-assembly (Chemistry)
- Description: Syntheses, spectral, electrochemical and spectroelectrochemical studies of phenylthio and amino derivatised metallophthalocyanines complexes are reported. The complexes are immobilized onto a gold macro disk, gold ultramicroelectrode and gold coated fiber electrodes via self assembly with phenylthio MPc derivatives or onto a glassy carbon electrode via electropolymerisation with amino MPc derivatives. For the first time MPc SAMs were formed on gold coated fiber. The electrocatalytic behavior of the modified electrodes was studied for the detection of nitrite and L-cysteine, all modified electrodes showed improved electrocatalytic oxidation compared to the unmodified electrode. The MPc complexes catalyzed nitrite oxidation via a two-electron mechanism producing nitrate. Cobalt tetraaminophthalocyanine showed the best catalytic activity for nitrite oxidation in terms of overpotential lowering compared to other complexes and thus was used for nitrite detection in a food sample, the nitrite concentration was determined to be 59.13 ppm, well within the limit for cured meat products. Electrocatalytic oxidation of L-cysteine on SAM modified gold coated fiber was reported for the first time. The gold coated fiber and ultamicro cylinder electrode were less stable towards the electro-oxidation of cysteine compared to its oxidation on the gold disk. The gold disk electrode gave better catalytic performance in terms of stability and reduction of overpotential. The phenylthio cobalt phthalocyanine derivative gave the best catalytic activity for L-cysteine oxidation in terms of overpotential lowering compared to other phenylthio derivatized MPc complexes. The amount of L-cysteine in human urine was 2.4 mM, well within the urinary L-cysteine excretion range for a healthy human being.
- Full Text:
- Date Issued: 2009
- Authors: Nombona, Nolwazi
- Date: 2009
- Subjects: Titanium , Manganese , Cobalt , Phthalocyanines , Electrochemistry , Electrodes , Self-assembly (Chemistry)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4312 , http://hdl.handle.net/10962/d1004970 , Titanium , Manganese , Cobalt , Phthalocyanines , Electrochemistry , Electrodes , Self-assembly (Chemistry)
- Description: Syntheses, spectral, electrochemical and spectroelectrochemical studies of phenylthio and amino derivatised metallophthalocyanines complexes are reported. The complexes are immobilized onto a gold macro disk, gold ultramicroelectrode and gold coated fiber electrodes via self assembly with phenylthio MPc derivatives or onto a glassy carbon electrode via electropolymerisation with amino MPc derivatives. For the first time MPc SAMs were formed on gold coated fiber. The electrocatalytic behavior of the modified electrodes was studied for the detection of nitrite and L-cysteine, all modified electrodes showed improved electrocatalytic oxidation compared to the unmodified electrode. The MPc complexes catalyzed nitrite oxidation via a two-electron mechanism producing nitrate. Cobalt tetraaminophthalocyanine showed the best catalytic activity for nitrite oxidation in terms of overpotential lowering compared to other complexes and thus was used for nitrite detection in a food sample, the nitrite concentration was determined to be 59.13 ppm, well within the limit for cured meat products. Electrocatalytic oxidation of L-cysteine on SAM modified gold coated fiber was reported for the first time. The gold coated fiber and ultamicro cylinder electrode were less stable towards the electro-oxidation of cysteine compared to its oxidation on the gold disk. The gold disk electrode gave better catalytic performance in terms of stability and reduction of overpotential. The phenylthio cobalt phthalocyanine derivative gave the best catalytic activity for L-cysteine oxidation in terms of overpotential lowering compared to other phenylthio derivatized MPc complexes. The amount of L-cysteine in human urine was 2.4 mM, well within the urinary L-cysteine excretion range for a healthy human being.
- Full Text:
- Date Issued: 2009
Studies towards the synthesis of novel tridentate ligands for use in ruthenium metathesis catalysts
- Authors: Millward, Tanya
- Date: 2009
- Subjects: Ligands , Catalysis , Metathesis (Chemistry) , Ruthenium , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4360 , http://hdl.handle.net/10962/d1005025 , Ligands , Catalysis , Metathesis (Chemistry) , Ruthenium , Complex compounds
- Description: This work has focussed on the preparation of a variety of tridentate ligands, designed to form ruthenium complexes as potential metathesis catalysts. Various approaches to the tridentate, malonate-tethered imidazolidine system have been investigated, and a promising route to accessing ligands of this type is discussed. A tridentate malonate-tethered pyridine ligand has been successfully prepared and its dithallium salt has been accessed by hydrolysis with thallium carbonate; approaches to a longer-chain analogue have also been investigated. A thallium pyridine-2,6- dicarboxylate ligand has been has been successfully prepared, as have a range of pyridine diamine ligands, with various alkyl and aromatic substituents on the amine donor atoms. Preliminary investigations into the potential of these compounds as ligands for alkylidene ruthenium complexes are reported using molecular modelling techniques. The geometries and steric energies of the ligands and their corresponding complexes have been analysed, and results obtained from two different software packages are compared. Finally, some preliminary complexation studies have been undertaken.
- Full Text:
- Date Issued: 2009
- Authors: Millward, Tanya
- Date: 2009
- Subjects: Ligands , Catalysis , Metathesis (Chemistry) , Ruthenium , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4360 , http://hdl.handle.net/10962/d1005025 , Ligands , Catalysis , Metathesis (Chemistry) , Ruthenium , Complex compounds
- Description: This work has focussed on the preparation of a variety of tridentate ligands, designed to form ruthenium complexes as potential metathesis catalysts. Various approaches to the tridentate, malonate-tethered imidazolidine system have been investigated, and a promising route to accessing ligands of this type is discussed. A tridentate malonate-tethered pyridine ligand has been successfully prepared and its dithallium salt has been accessed by hydrolysis with thallium carbonate; approaches to a longer-chain analogue have also been investigated. A thallium pyridine-2,6- dicarboxylate ligand has been has been successfully prepared, as have a range of pyridine diamine ligands, with various alkyl and aromatic substituents on the amine donor atoms. Preliminary investigations into the potential of these compounds as ligands for alkylidene ruthenium complexes are reported using molecular modelling techniques. The geometries and steric energies of the ligands and their corresponding complexes have been analysed, and results obtained from two different software packages are compared. Finally, some preliminary complexation studies have been undertaken.
- Full Text:
- Date Issued: 2009
Synthesis and electrochemistry of octapentylthio phthalocyanine complexes of manganese, titanium and vanadium
- Authors: Mbambisa, Gcineka
- Date: 2009
- Subjects: Electrochemistry , Phthalocyanines -- Synthesis , Manganese , Titanium , Vanadium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4368 , http://hdl.handle.net/10962/d1005033 , Electrochemistry , Phthalocyanines -- Synthesis , Manganese , Titanium , Vanadium
- Description: Synthesis of new thio derivatised Pcs with manganese, titanium and vanadium as a central metal is reported. The complexes synthesised were characterised using spectroscopic and electrochemical means. The complexes displayed interesting spectroscopic properties with absorption of the Q band being observed in the near infrared region. These complexes have unusual colours for MPc complexes, with purple or red colour being observed in solution. Interesting electrochemical properties were observed, with rare observation of the MnIV/MnIII redox couple. There was observation of oxidation peaks for the pentylthio derivatised Pc with titanium as the central metal; this is unusual since for reported thio derivatives based on TiPc, no oxidation was observed. The vanadium based Pc showed an interesting spectrum for the first ring based reduction. The absorption spectrum obtained for the 1st reduction of the vanadium complex using spectroelectrochemistry would normally indicate a metal based process but comparing with literature it was concluded that it is a ring based reduction process. Generally all the MPc complexes formed a well ordered stable monolayer on the gold electrode. Electrocatalytic studies using L-cysteine revealed that the SAM based on manganese (III) octapentylthio phthalocyanine (AcOMnOPTPc) was the most effective since it catalyses L-cysteine at much lower oxidation potentials and it is also much more stable.
- Full Text:
- Date Issued: 2009
- Authors: Mbambisa, Gcineka
- Date: 2009
- Subjects: Electrochemistry , Phthalocyanines -- Synthesis , Manganese , Titanium , Vanadium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4368 , http://hdl.handle.net/10962/d1005033 , Electrochemistry , Phthalocyanines -- Synthesis , Manganese , Titanium , Vanadium
- Description: Synthesis of new thio derivatised Pcs with manganese, titanium and vanadium as a central metal is reported. The complexes synthesised were characterised using spectroscopic and electrochemical means. The complexes displayed interesting spectroscopic properties with absorption of the Q band being observed in the near infrared region. These complexes have unusual colours for MPc complexes, with purple or red colour being observed in solution. Interesting electrochemical properties were observed, with rare observation of the MnIV/MnIII redox couple. There was observation of oxidation peaks for the pentylthio derivatised Pc with titanium as the central metal; this is unusual since for reported thio derivatives based on TiPc, no oxidation was observed. The vanadium based Pc showed an interesting spectrum for the first ring based reduction. The absorption spectrum obtained for the 1st reduction of the vanadium complex using spectroelectrochemistry would normally indicate a metal based process but comparing with literature it was concluded that it is a ring based reduction process. Generally all the MPc complexes formed a well ordered stable monolayer on the gold electrode. Electrocatalytic studies using L-cysteine revealed that the SAM based on manganese (III) octapentylthio phthalocyanine (AcOMnOPTPc) was the most effective since it catalyses L-cysteine at much lower oxidation potentials and it is also much more stable.
- Full Text:
- Date Issued: 2009
Synthesis and photophysical properties of antimony and lead phthalocyanines
- Modibane, Kwena Desmond, Guest
- Authors: Modibane, Kwena Desmond , Guest
- Date: 2009 , 2009-02-27
- Subjects: Phthalocyanines , Photochemistry , Antimony compounds , Lead compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4370 , http://hdl.handle.net/10962/d1005035 , Phthalocyanines , Photochemistry , Antimony compounds , Lead compounds
- Description: This work hereby presents the synthesis, spectroscopic and photophysical properties of newly synthesized lead (PbPc) and antimony (SbPc) phthalocyanines. The complexes are either unsubstituted or substituted at the peripheral and non-peripheral positions with phenoxy, 4-t-butylphenoxy and 4-benzyloxyphenoxy groups. The photophysical properties of these complexes were studied in dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform as solvents. The fluorescence spectra for PbPc complexes were different to that of the excitation spectra due to demetallation upon excitation. On the other hand, the excitation spectra of oxidized antimony (Sb(V)Pc) derivatives were found to be similar to absorption spectra. High triplet quantum yields for PbPc and SbPc complexes ranging from 0.70 to 0.86, low triplet lifetimes (20–60 μs in DMSO, while they were <10 μs in the rest of the solvents) and low fluorescence quantum yields were observed and is attributed to the presence of heavy atoms (Pb and Sb ions). The nonlinear optical properties of PbPc complexes were studied in dimethylsulfoxide. The optical limiting threshold intensity (Ilim) for the PbPc derivatives were calculated and ranged from 2.1 to 6.8 W/cm2. The photodegradation studies of the PbPc and SbPc complexes synthesized showed that then are stable.
- Full Text:
- Date Issued: 2009
- Authors: Modibane, Kwena Desmond , Guest
- Date: 2009 , 2009-02-27
- Subjects: Phthalocyanines , Photochemistry , Antimony compounds , Lead compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4370 , http://hdl.handle.net/10962/d1005035 , Phthalocyanines , Photochemistry , Antimony compounds , Lead compounds
- Description: This work hereby presents the synthesis, spectroscopic and photophysical properties of newly synthesized lead (PbPc) and antimony (SbPc) phthalocyanines. The complexes are either unsubstituted or substituted at the peripheral and non-peripheral positions with phenoxy, 4-t-butylphenoxy and 4-benzyloxyphenoxy groups. The photophysical properties of these complexes were studied in dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform as solvents. The fluorescence spectra for PbPc complexes were different to that of the excitation spectra due to demetallation upon excitation. On the other hand, the excitation spectra of oxidized antimony (Sb(V)Pc) derivatives were found to be similar to absorption spectra. High triplet quantum yields for PbPc and SbPc complexes ranging from 0.70 to 0.86, low triplet lifetimes (20–60 μs in DMSO, while they were <10 μs in the rest of the solvents) and low fluorescence quantum yields were observed and is attributed to the presence of heavy atoms (Pb and Sb ions). The nonlinear optical properties of PbPc complexes were studied in dimethylsulfoxide. The optical limiting threshold intensity (Ilim) for the PbPc derivatives were calculated and ranged from 2.1 to 6.8 W/cm2. The photodegradation studies of the PbPc and SbPc complexes synthesized showed that then are stable.
- Full Text:
- Date Issued: 2009
The design and synthesis of novel HIV-1 protease inhibitors
- Authors: Tukulula, Matshawandile
- Date: 2009
- Subjects: Protease Inhibitors HIV infections -- Treatment AIDS (Disease) -- Treatment HIV (Viruses) Indolizine -- Derivatives Heterocyclic compounds -- Derivatives Nuclear magnetic resonance Quinoline
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4305 , http://hdl.handle.net/10962/d1004963
- Description: This study has focused on the synthesis of truncated analogues of the hydroxyethylene dipeptide isosteres, such as Ritonavir®, currently in clinical use as HIV-1 protease inhibitors. The reactions of pyridine-2- and quinoline-2-carbaldehydes with methyl acrylate, in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) or 3- hydroxyquinuclidine (3-HQ) as nucleophilic catalysts, have afforded a series of Baylis- Hillman adducts, acetylation and cyclisation of which have provided access to a series of indolizine-2-carboxylate esters. The carboxylic acids, obtained by base-catalyzed hydrolysis of these esters, have been coupled with various protected (and unprotected) amino compounds using the peptide coupling agent, 1,1’-carbonyldiimidazole (CDI), to afford a series of indolizine-2-carboxamides as indolizine-based truncated Ritonavir® analogues in quantitative yield. Aza-Michael reactions of pyridine-3-carbaldehydederived Baylis-Hillman adducts with various amino compounds have provided access to a range of pyridine-based products as mixtures of diastereomeric aza-Michael products. The assignment of the relative stereochemistry of the aza-Michael products has been established using 1-D and 2-NOESY experiments and computer modelling techniques. Computer modelling studies have also been conducted on selected aza-Michael products using ACCELRYS Cerius2 software, followed by interactive docking into the HIV-1 protease receptor site, using AUTODOCK 4.0. The docking studies have revealed hydrogen-bonding interactions between the enzyme and the synthetic ligands. Saturation Transfer Difference (STD) NMR experiments have also indicated binding of some of the aza-Michael products to the HIV-1 protease subtype C enzyme, thus indicating their binding and possible inhibitory potential.
- Full Text:
- Date Issued: 2009
- Authors: Tukulula, Matshawandile
- Date: 2009
- Subjects: Protease Inhibitors HIV infections -- Treatment AIDS (Disease) -- Treatment HIV (Viruses) Indolizine -- Derivatives Heterocyclic compounds -- Derivatives Nuclear magnetic resonance Quinoline
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4305 , http://hdl.handle.net/10962/d1004963
- Description: This study has focused on the synthesis of truncated analogues of the hydroxyethylene dipeptide isosteres, such as Ritonavir®, currently in clinical use as HIV-1 protease inhibitors. The reactions of pyridine-2- and quinoline-2-carbaldehydes with methyl acrylate, in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) or 3- hydroxyquinuclidine (3-HQ) as nucleophilic catalysts, have afforded a series of Baylis- Hillman adducts, acetylation and cyclisation of which have provided access to a series of indolizine-2-carboxylate esters. The carboxylic acids, obtained by base-catalyzed hydrolysis of these esters, have been coupled with various protected (and unprotected) amino compounds using the peptide coupling agent, 1,1’-carbonyldiimidazole (CDI), to afford a series of indolizine-2-carboxamides as indolizine-based truncated Ritonavir® analogues in quantitative yield. Aza-Michael reactions of pyridine-3-carbaldehydederived Baylis-Hillman adducts with various amino compounds have provided access to a range of pyridine-based products as mixtures of diastereomeric aza-Michael products. The assignment of the relative stereochemistry of the aza-Michael products has been established using 1-D and 2-NOESY experiments and computer modelling techniques. Computer modelling studies have also been conducted on selected aza-Michael products using ACCELRYS Cerius2 software, followed by interactive docking into the HIV-1 protease receptor site, using AUTODOCK 4.0. The docking studies have revealed hydrogen-bonding interactions between the enzyme and the synthetic ligands. Saturation Transfer Difference (STD) NMR experiments have also indicated binding of some of the aza-Michael products to the HIV-1 protease subtype C enzyme, thus indicating their binding and possible inhibitory potential.
- Full Text:
- Date Issued: 2009
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