Masters Degrees (Chemistry)

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Browsing Masters Degrees (Chemistry) by Advisor "Conradie, J."

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    Synthesis, characterization and electrochemistry of phthalocyanine derivatives with biomedical applications
    (University of the Free State, 2016) Oosthuizen, Dina Naudé; Fourie, E.; Swarts, J. C.; Conradie, J.
    English: A series of metal-free phthalocyanines, with ethylene glycol and alkyl peripheral and nonperipheral substituents, were synthesized and characterized with the aid of 1H NMR, IR and UV/vis spectroscopy. The electrochemical study (cyclic voltammetry) showed smaller peak potentials for phthalocyanines with shorter ethylene glycol substituents, thus the shorter the ethylene glycol chain, the higher the electron density of the macrocycle. Electrochemical (cyclic, square wave and linear sweep voltammetry) and computational (including the determination of relevant geometries and molecular orbitals) studies were done on a series of ruthenium phthalocyaninato complexes. A comparison of the peak oxidation potential of the first experimental oxidation process and computed energy of the highest occupied molecular orbitals (HOMO) for the series of (CO)RuPc, showed a linear correlation.. An RC1 reactor was used to study the hydrogenation reaction of 4-nitrophthalonitrile as weak as the oxidation reaction of 2,5-dihexylthiophene and 2,5didodecylthiophene utilizing dimethyldioxirane of oxidizing agent. By making use of the RC1 reactor, the reactions were followed kinetically and thermodynamically, yielding rate constants as well as reaction enthalpies. These results were compared to theoretical reaction enthalpies determined by DFT calculations. Good correlation was found between the experimentally obtained reaction enthalpies and theoretical reaction enthalpies.
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    Synthesis, electrochemical, kinetic and thermodynamic properties of new ferrocene-containing betadiketonato rhodium(I) complexes with biomedical applications
    (University of the Free State, 2002-11) Klaas, Palesa; Swarts, J. C.; Conradie, J.
    English: Synthetic routes to prepare new ferrocene-containing β-diketones, FcCOCH2COR, with Fc = ferrocenyl, R = H, CH3, CH2CH3, CH(CH3)2 and C(CH3)3, have been developed. Rhodium complexes of the type [Rh(FcCOCHCOR)(cod)] were obtained in yields approaching 80% by treating these β-diketones with [Rh2Cl2-(cod)2]. Group electronegativities XR of R substituents were determined from a linear relationship between ethyl ester IR carbonyl stretching frequencies of the type RCOOCH2CH3 and group electronegativities of known R groups. pKa values of new β -diketones were determined. 1H NMR studies on FcCOCH2COR indicated that enolisation in the direction furthest from the ferrocenyl group always dominate. This finding is considered to be the result of resonance driving force rather than inductive electronic effects of substituents on the pseudo-aromatic β-diketone core. Formal reduction potentials (Eol values vs. Ag/Ag+) of the iron core in the free β-diketones, FcCOCH2COR, and in [Rh(FcCOCHCOR)(cod)] complexes as well as the peak anodic oxidation potentials, Epa, of the rhodium(I) nucleus were determined. The roles of pKa and group electronegativities on redox potentials are also discussed. Second-order rate constants, k2, for the substitution of the β-diketonato ligand, (FcCOCHCOR), from the complexes [Rh(FcCOCHCOR)(cod)] with 1,10-phenanthroline at 25°C in methanol were determined. Large negative values obtained for entropy of activation suggested an associative substitution mechanism. All substitution reactions were independent of a solvent step. Cytotoxic properties in terms of potential anticancer applications of these newly synthesised β- diketones and their rhodium complexes on cancer cells are described. Cytotoxicity was tested on HeLa, A2780 and A2780 platinum resistant cancer cells lines. Rhodium complexes were observed to be more effective in killing cancer cells than the free β-diketones.
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    Synthesis, electrochemical, kinetic and thermodynamic studies of new ruthenocene-containing betadiketonato rhodium(I) complexes with biomedical applications
    (University of the Free State, 2004-05) Kemp, Kingsley Christian; Swarts, J. C.; Conradie, J.
    English: New ruthenocene-containing β -diketones 1-Ruthenocenyl-4,4,4,-trifluorobutan-1,3-dione [Hrctfa, pKa / = 7.31(3)], 1-ruthenocenylbutan-1,3-dione [Hrca, pKa / = 10.22(4)] 1-ruthenocenyl-3- phenylpropan-1,3-dione [(Hbrcm, pKa / = 11.31(4)], 1-ruthenocenyl-3-ferrocenylpropan-1,3-dione [(Hrcfcm; pKa / >13)], and 1,3-diruthenocenylpropane-1,3-dione [(Hdrcm, pKa / >13)], were prepared by the Claisen Condensation of acetylruthenocene and the appropriate ester under the influence of lithium diisopropylamide. The group electronegativity of the ruthenocenyl group (Rc) was determined from the linear relationship between the methyl ester (RCOOMe) infrared carbonyl stretching frequencies and the group electronegativities of known R groups, R = CF3, CH3, C5H5, H, Fc. The [Rh(β -diketonato)(cod)] complexes [Rh(rctfa)(cod)], [Rh(rca)(cod)], [Rh(brcm)(cod)], [Rh(rcfcm)(cod)] and [Rh(drcm)(cod)] were obtained by treating the appropriate β -diketones (Hrctfa, Hrca, Hbrcm, Hrcfcm and Hdrcm) with [Rh2(cod)2Cl2]. Kinetics results for the conversion of the β -diketones (Hrctfa, Hrca, Hbrcm, Hrcfcm and Hdrcm) from the enol to the keto form and vice versa are reported. Kinetics results for the substitution of β -diketonato ligand from the [Rh(β -diketonato)(cod)] complexes ( [Rh(rctfa)(cod)], [Rh(rca)(cod)], [Rh(brcm)(cod)], [Rh(rcfcm)(cod)] and [Rh(drcm)(cod)]) with 1,10-phenantroline in methanol are also presented. Large negative activation entropy values obtained, suggested an associative substitution mechanism. All substitution reactions had no observable mechanistic solvent pathway contribution. Oxidation potentials (Epa vs Ag/Ag + ) for the ruthenium core in the free β -diketones (Hrctfa, Hrca, Hbrcm, Hrcfcm and Hdrcm), as well as in the [Rh(β -diketonato)(cod)] complexes ([Rh(rctfa)(cod)], [Rh(rca)(cod)], [Rh(brcm)(cod)], [Rh(rcfcm)(cod)] and [Rh(drcm)(cod)]) are reported. The peak anodic potentials (Epa vs Ag/Ag + ) for oxidation of the rhodium(I) center were determined.
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    Synthesis, electrochemistry and density functional theory calculations on chrome and cobalt carbene and betadiketonato complexes
    (University of the Free State, 2014) Liu, Renyuan; Conradie, J.
    English: Two series of metal(β-diketonato)3 complexes were synthesized: tris(β-diketonato)chromium(III) complexes (where β-diketonato = [R1COCHCOR2]- = acac, ba, dbm, tfba, tfth, tffu, tfaa, hfaa) and tris(β-diketonato)cobalt(III) complexes (where β-diketonato = acac, ba, dbm, tfba, tfaa). These paramagnetic complexes were characterized by mass spectroscopy, X-ray crystallography and melting point measurements. The electrochemical behaviour of tris(β- diketonato)chromium(III) complexes was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and square wave voltammetry (SWV). The reduction potentials of the CrIII(β-diketonato)3 → CrII(β-diketonato)3 process correlate linearly with the following electronic parameters: 1) the acid dissociation constant (pKa) of the uncoordinated β-diketonato ligands, 2) the total electronegativities (Σx) of the side groups (R1 and R2) on the β-diketonato ligands, and 3) the total Hammett sigma constant (Σσ) of the side groups (R1 and R2) on the β-diketonato ligands. DFT-calculations were done on both series of these metal(β-diketonato)3 complexes. Molecular geometry, spin state and respective population of possible isomers were calculated in this study. The understanding of crystal structures was complemented by using DFT-results. For CrIII(β-diketonato)3 complexes, linear dependence was found between their reduction potentials and electron affinity (EA), as well as between reduction potentials and the energies of the lowest unoccupied molecular orbitals (ELUMO). Electrochemical behaviour of chromium(0) carbene complexes was investigated by cyclic voltammetry. The difference in oxidation potential of fac/mer isomers was observed for the first time for chromium(0) carbene complexes and discussed in this study. DFT-calculations revealed the following linear relationships with the redox process of Cr(0) carbene complexes: 1) the linear dependence between the cathodic potential (Epc) and energies of the lowest unoccupied orbitals (ELUMO), and 2) the linear dependence between the anodic potential (Epa) and energies of the highest occupied orbitals (EHOMO).