A series of SNS ligands have been successfully synthesised and characterised by IR, NMR and MS. The ligands are divided into two groups and represented by the general formulae: 2,6- bis(RSCH2)pyridine [R= methyl, ethyl, butyl, cyclohexyl, phenyl] and bis(RSCH2CH2)amine [R= ethyl, butyl, decyl]. Cobalt complexes of the respective ligands with the general formulae Co[2,6-bis(RSCH2)pyridine]Cl2 and Co[bis(RSCH2CH2)amine]Cl2 were synthesised and characterised by IR, elemental analysis and X-ray crystallography (for selected complexes). Thus, to investigate the electronic and steric effects of the ligand structure on the chemistry and reactivity of the complexes, the substituents bonded to the two sulfur donor atoms were sequentially varied and two different nitrogen sources were chosen. Crystal structures of Co[2,6- bis(CH2SCH2)pyridine]Cl2 (Ia), Co[2,6-bis(CH2CH2SCH2) pyridine]Cl2 (IIa) and Co[2,6- bis(CH2CH2CH2CH2SCH2)pyridine]Cl2 (IIIa) were obtained. It was found that complex Ia exists as a molecular dimer linked through two chloride bridges resulting in an octahedral geometry around each metal centre, while complexes IIa and IIIa are monomers exhibiting a trigonal bypyrimidal geometry. The complexes were tested as catalysts for the activation of paraffinic C−H bonds towards the formation of oxygenated products: octanol, octanone, octanal and octanoic acid from the substrate n-octane. Gas chromatography was utilised to quantify the products formed and also to calculate the conversion and selectivity of each catalyst system. The catalytic testing revealed that the ketone products were the most dominant with selectivities of ca. 90%. The catalyst that was the most active was Co[bis(CH2CH2SCH2CH2)amine]Cl2 (Ib) with a total n-octane conversion of 23%. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2012.

This study covered both the Hass and Fuerte varieties of avocado pears. The quality of extracted avocado oil produced by different extraction techniques was assessed to determine the effect the extraction method had on the nutritional and storage value of the oil. While microwave extraction produced the highest yield of oil (70.0 %), supercritical fluid extraction produced oil with a wider range of fatty acids. Although the Hass variety produced a higher oil yield, oil extracted from the Fuerte variety was shown to have a higher monounsaturated fatty acid to saturated fatty acid ratio, which makes the latter oil more beneficial to health. Oils of the Fuerte variety also possessed a higher concentration of co-extracted metals, which makes it more susceptible to lipid oxidation. The overall choice for the most efficient extraction method was microwave extraction as it produced the highest yield and quality of oil. The impact of soil quality on elemental uptake into locally grown avocado fruit sampled from six different locations was determined. Of the 14 selected metals investigated, avocado fruit was found not to accumulate Cd, Co, Cr, Pb and Se. Generally, the concentration of elements in both varieties of fruit was in the order of Mg > Ca > Al > Zn > Fe > Mn > Cu > Ni > As. Relative bioaccumulation plots were used to establish the essential and non-essential elements for normal growth of avocado fruit. It was found that the plant has an involuntary uptake mechanism for As due to similarity in ion species to P, which is an essential element. The impact of soil quality parameters pH, cation exchange capacity and soil organic matter were determined and their impact on plant-soil interactions was analysed. Statistical analysis revealed a plethora of metal interactions at the plant-soil interface. However, the plant was still seen to control uptake of specific elements such as Cu, Fe and Ca, due to its physiological requirements. CEC was found to have a greater effect on availability of elements than pH and SOM. Geoaccumulation indices indicated moderate enrichment of Pb in soils; however this result had no bearing on the elemental uptake of the fruit at all sites. Comparisons to recommended dietary allowances (RDAs) for human diet reveal the average contribution of avocado to be 70% and 45% for Cu and Mn, respectively. Low levels of As was found in fruit which warrants continued monitoring of this element in the plant due to its similarity to P. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2011.

Os-Zn-Al hydrotalcite-like compounds (HTlc’s) were synthesised by the co-precipitation method and characterised using different techniques (powder XRD, ICP-OES, FT-IR spectroscopy, BET-surface area measurements, SEM and SEM-EDS, cryo-TEM, 27Al SS-NMR and TGA-DSC). The hydrotalcite-like catalyst was used to heterogenise the aminohydroxylation reaction. Among the three solvents investigated (toluene, MeCN/water (1:1 v/v) and t- BuOH/water (1:1 v/v)) in the aminohydroxylation reaction, toluene showed the slowest reaction rate, MeCN/water (1:1 v/v) and t-BuOH/water (1:1 v/v) demonstrated fast reaction rates comparable to each other. The reaction temperature was only significant when toluene was used as the solvent system (reaction time (100% depletion of starting material) and temperature are inversley proportional). The catalyst HTlc structure demonstrated a significant effect in terms of the reaction time and isolated yield of the -amino alcohols. Under the same testing conditions a heat treated catalyst (non-HTlc) showed a shorter reaction time, a reduction in the isolated yield of -amino alcohols with a rise in diol formation. All the different classes of olefins (aliphatic, aromatic, and functionalised) that were tested, gave 99.99% depletion of starting material. However, due to the same purification difficulties encountered in the homogeneous amino hydroxylation (AA) reaction, the isolated yield of -amino alcohols achieved here, ranged from 13 to 35 %, with the highest yield (35%) obtained when methylcinnamate was used as the olefin. Characterisation of the spent catalyst showed that HTlc structure is maintained, but crystallinity was lost (the material becomes polycrystalline) after the reaction. The leaching test showed that 4.5% and 5.5% of Os leached from the catalyst to the reaction solution when MeCN/water (1:1 v/v) and t-BuOH /water (1:1 v/v) were used as the solvent system, respectively. The leached form of Os was determined to be inactive, indicating that this system is truly heterogeneous. The recycling study (three cycles) indicated that the catalyst can be recycled, but with a decrease in the reaction rate (which could be due to structure defects and loss of crystallinity), and with no significant difference in the isolated yield of the amino-alcohol. The crystal structure of three -amino alcohols are also reported. The crystal structure of the - amino alcohol of cyclohexene, methylcinnamte and t-butylcrotonate were needle-like triclinic, pi, needle-like monoclinic, p21/c and cubic-like triclinic, p-1, respectively. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / The focus of this study was the pathways for β-alanine production in Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis. The major pathway for β-alanine production is the decarboxylation of L-aspartate by L-aspartate-α-decarboxylase (PanD). This enzyme is not essential for the survival for Mtb which implies that an alternative pathway for β-alanine production must exist. We postulated that such a secondary pathway may be based on the oxidation of various polyamines by a polyamine oxidase to give the β-alanine precursor 3-aminopropanal, and therefore set out to find data in support of this hypothesis. Based on sequence homology to the FAD-dependent Saccharomyces cerevisiae polyamine oxidase Fms1, Mtb AofH was identified as a likely candidate. The soluble expression and purification of AofH proved troublesome and lead to the investigation of various techniques to increase protein yield. These methods include fusion to various tags, coexpression with the protein chaperones, addition of scarce codon tRNA’s to the translation mixture and protein refolding. AofH was eventually purified as fusions to the Nus and MBP proteins and its activity determined by analysis of the enzymatic reactions by TLC, reverse phase HPLC, ESI-MS and LC-MS. TLC analysis indicated that 3- aminopropanol formed as a product during polyamine oxidation, but this could not be confirmed by any of the more sensitive analytical techniques. We set out to confirm the presence of the FAD cofactor in the enzyme by various methods and concluded that the AofH fusions did not contain FAD. Efforts to refold the protein in the presence of FAD also failed. From this study it is clear that the biochemical confirmation of the presumed activity of AofH will remain elusive until the enzyme can be purified in its active form, i.e. with FAD bound. A genetic test for activity based on functional complementation studies of Escherichia coli ΔpanD strains proved inconclusive since no difference in growth rate was found between cell transformed with the aofH gene and the negative control. We continued our studies of β-alanine biosynthesis by attempting the design of mechanism-based inhibitors for the PanD enzyme. Various structural analogues were identified and tested by qualitative and quantitative methods. Our results show that β- substituted aspartate analogues may be good potential inhibitors of Mtb’s PanD protein and can thus be used in rational drug design.

Thesis (MSc)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The equilibrium distribution coefficients of 42 elements [Li(I), Na(I), K(I), Rb(I), Cs(I), Sc(III), Ti(IV), V(IV), V(V), Mn(II), Fe(III), Ni(II), Zn(II), Al(III), Ga(III), As(V), Y(III), Zr(IV), Nb(V), Mo(VI), Cd(II), In(III), Sn(IV), Sb(V), Ta(V), W(VI), Pb(II), Bi(III), La(III), Ce(III), Th(IV), U(VI), Co(II), Ag(I), Ge(IV),Mg(II), Sr(II), Ba(II), Tb(III), Yb(III), Cr(III) and Cu(II)] on Bio Rad AG MP-50 macroporous cation exchange resin in varying citric acid – nitric acid mixtures were successfully determined. The equilibrium distribution coefficients of these selected elements were determined in 0.1 M and 0.25 M citric acid at various concentrations of nitric acid, namely, 0.2 M, 0.5 M, and 1.0M, respectively. Two component [Mo(VI)-Y(III); Zr(IV)-La(III) and As(V)-Zn(II)] and three component [Nb(V)-Ta(V)-V(V)] elemental separations on a 10 ml AG MP-50 resin column were successfully determined to illustrate how the results of the above equilibrium distribution coefficients can be utilised. From the equilibrium distribution coefficients obtained for magnesium(II) and sodium(I), a proposal was put forward to modify the current sodium-22 production performed at iThemba LABS. While the results did not predict a possible separation between the two elements, a theory concerning the use of citric acid in the production was proven not to hold under the chosen conditions. / AFRIKAANSE OPSOMMING: Die ewewig verdelingskoëffisiënte van 42 elemente [Li(I), Na(I), K(I), Rb(I), Cs(I), Sc(III), Ti(IV), V(IV), V(V), Mn(II), Fe(III), Ni(II), Zn(II), Al(III), Ga(III), As(V), Y(III), Zr(IV), Nb(V), Mo(VI), Cd(II), In(III), Sn(IV), Sb(V), Ta(V), W(VI), Pb(II), Bi(III), La(III), Ce(III), Th(IV), U(VI), Co(II), Ag(I), Ge(IV),Mg(II), Sr(II), Ba(II), Tb(III), Yb(III), Cr(III) en Cu(II)] is op Bio Rad se AG MP-50 makroporeuse kationiese uitruilerhars in verskillende sitroensuur – salpetersuur mengsels met sukses bepaal. Die verdelingskoëffisiënte is in 0.1 M en 0.25 M sitroensuur met verskillende konsentrasies van salpetersuur (0.2 M, 0.5 M en 1.0 M) bepaal. Twee-komponent [Mo(VI)-Y(III); Zr(IV)-La(III) en As(V)-Zn(II)] en drie-komponent [Nb(V)-Ta(V)-V(V)] skeidings op ’n 10 ml AG MP-50 harskolom is suksesvol bepaal om te demonstreer hoe die verdelingskoëffisiëntresultate gebruik kan word. As ’n uitvloeisel van die verdelingskoëffisiëntresultate vir Mg(II) en Na(I), is ’n voorstel ingedien om die huidige natrium-22 produksiemetode, tans in gebruik by iThemba LABS, te modifiseer. Die resultate het nie ’n skeiding tussen die twee elemente voorspel nie, maar het bewys dat ’n teorie oor die gebruik van sitroensuur in die produksie nie heeltemal korrek was onder die huidige toestande nie.

Thesis (MSc)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: This investigation comprised the synthesis and characterisation of new Au(I) phosphonium ylide complexes and other compounds formed during coordination reactions. These complexes could exploit the synergism between two pharmacologically active substances (gold complex unit and phosphorus ylide) to furnish an even more active substance. Four phosphonium salts were prepared, [C6H5CH2PPh3]Br (1), [Ph3P(CH2)3PPh3]Br2 (2a), p-[{Ph3PCH2}2C6H4]Br2 (3a) and m- [{Ph3PCH2}2C6H4]Br2 (4a), by reacting PPh3 with the corresponding alkylbromides. The 13C and 1H NMR spectra of the compounds 1 – 4a indicated that many of the nuclei are magnetically inequivalent. The aromatic units in PPh3 are normally identical, but multiple, overlapping signals proved that the corresponding ortho, meta and para carbon and proton nuclei are in magnetically different environments from each other. Single crystal structures of salts 3a and 4a were determined. Different methods were followed to deprotonate the phosphonium salts to afford the corresponding ylides and to coordinate the ylides to gold precursor compounds. Most of the reactions yielded inseparable mixtures of products and pure compounds could not be isolated in large enough quantities for characterisation by all physical methods. Sufficient crystals for structure determination by X-ray diffraction were obtained. The product mixtures were characterised by 1H, 13C and 31P NMR spectroscopy and mass spectrometry. Characteristic downfield chemical shift changes after coordination of the ylides to Au(I) were observed for the carbon and phosphorus nuclei, while the protons displayed upfield shifts. Reaction of (C6F5)Au(tht) with the salts 1 – 4a, and subsequent deprotonation yielded the gold(I) ylide complexes [C6H5CH(AuC6F5)PPh3] (5), [{Ph3PCH(AuC6F5)}2CH2] (6), p-[{Ph3PCH(AuC6F5)}2C6H4] (8), and m- [{Ph3PCH(AuC6F5)}2C6H4] (9). The crystal and molecular structures of compounds 5 and 9 were determined. Deprotonation of 4a with n-BuLi, followed by reaction with (C6F5)Au(tht) yielded complexes 9 and [{Ph3PCH2}2C6H4][BrAuC6F5]2 (10). The crystal structure of compound 10 was determined. Two aurocyclic compounds, [μ- {(Ph3PCH)2CH2}2Au2][BF4]2 (12) and [μ–{(Ph3PCH)2C6H4}2Au2][BF4]2 (13) were synthesised by deprotonating salts 2b and 3b with n-BuLi and subsequently reacting the corresponding bisylides with ClAu(tht). Reaction procedures in which Ag2O was used as deprotonating agent for the phosphonium salts 2a, 3a and 4a, yielded mixtures of products. Single crystals of complexes m-[Ph3PCH(AuC6F5)C6H4CH3] (14), [C6F5Au(tht)] (15) and [(C6F5)2Au][(Ph3PCH2)2C6H4] (16) were isolated from the reaction mixtures and subjected to X-ray crystal structure determination. The molecular structure of 15 exhibited unusual aurophilic interactions and represents the first example of a linear gold chain in which the gold···gold distances systematically alternate between 3.13Å, 3.31Å and 3.20Å. Salt 2b was reacted with Ph3PAu(acac) to afford the desired compound, [{Ph3PCH(AuPPh3)}2CH2](BF4)2 (19), along with [CH3C(O)C(AuPPh3)2C(O)CH3] (17) and some byproducts. Compound 17 was characterised by single crystal Xray diffraction. The fluorobiphenylgold(I) complexes, 4,4’-[(AuPPh3)2C12F8] (21) and 2,2’- [(AuPPh3)2C12F8] (22) were synthesised by reaction of ClAuPPh3 with the lithiated 2,2’-dibromooctafluorobiphenyl and 4,4’-dibromooctafluorobiphenyl respectively. The molecular structure of 21 revealed that one of the C–Au–P bond angles deviates from linearity by 12.5°, probably as a result of π-stacking of the tetrafluorophenyl rings and steric requirements of the bulky PPh3 units. The other C–Au–P bond angle is linear [177.9(3)°]. / AFRIKAANSE OPSOMMING: Hierdie studie behels die sintese en karakterisering van nuwe fosfoniumylied goud(I)-komplekse en ander verbindings wat gedurende koördinasiereaksies vorm. Sulke komplekse kan sinergisme tussen twee farmakologies-aktiewe entiteite (goud(I) en fosfoniumylied) om ʼn meer aktiewe verbinding te vorm meebring. Vier fosfoniumsoute is berei, [C6H5CH2PPh3]Br (1), [Ph3P(CH2)3PPh3]Br2 (2a), p- [{Ph3PCH2}2C6H4]Br2 (3a) en m-[{Ph3PCH2}2C6H4]Br2 (4a), deur PPh3 met die ooreenstemmende alkielbromiedes te reageer. Die 13C- en 1H- KMR-spektra van dié verbindings toon dat ʼn aantal kerne in aromatiese ringe magneties onekwivalent is. Normaalweg is die koolstowwe in PPh3-eenhede ekwivalent, maar meervoudige, oorvleuelende pieke het nou getoon dat die ooreenstemmende orto-, meta- en para-koolstof sowel as die ooreenstemmende protonkerne in verskillende magnetiese omgewings voorkom. Die kristalstrukture van die soute 3a en 4a hierbo is met behulp van X-straal tegnieke bepaal. Verskillende metodes is gevolg om die fosfoniumsoute te deprotoneer na die ooreenstemmende yliede en om die yliede dan aan goud-bevattende uitgangstowwe te probeer koördineer. Die meeste reaksies het nie-skeibare mengsels gevorm en enkelprodukte kon nie in groot genoeg konsentrasies geïsoleer word om hulle afsonderlik te karakteriseer nie. Kristalle vir X-straal kristalstruktuur bepalings is verkry. Die produkmengsels is gekarakteriseer met behulp van 1H-, 13C- en 31P- KMR-spektroskopie en massaspektrometrie. Karakteristieke veranderinge in chemiese verskuiwings na laer veldsterktes vir die koolstof en fosfor kerne is waargeneem na koördinasie van die yliede aan Au(I), terwyl die protone na höer veldsterktes verskuif het. Die reaksie tussen (C6F5)Au(tht) (tetrahidrotiofeen) en soute 1 – 4a gevolg deur deprotonering, vorm die goud-yliedkomplekse [C6H5CH(AuC6F5)PPh3] (5), [{Ph3PCH(AuC6F5)}2CH2] (6), p-[{Ph3PCH(AuC6F5)}2C6H4] (8), en m- [{Ph3PCH(AuC6F5)}2C6H4] (9). Die kristalstrukture van komplekse 5 en 9 het al die molekulêre interaksies daarin blootgelê. Deprotonering van 4a met n-BuLi, gevolg deur reaksie met (C6F5)Au(tht) lewer komplekse 9 en [{Ph3PCH2}2C6H4][BrAuC6F5]2 (10). Die kristal- en molekulêre struktuuur van kompleks 10 is bepaal. Twee aurosikliese verbindings, [μ- {(Ph3PCH)2CH2}2Au2][BF4]2 (12) en [μ–{(Ph3PCH)2C6H4}2Au2][BF4]2 (13) is gesintetiseer deur gedeprotoneerde bisyliede verkry van 2b en 3b met substitusie van tht aan die ClAu-eenheid te koördineer. Reaksieprosedures waarin Ag2O vir deprotonering van die fosfoniumsoute 2a, 3a en 4a gebruik is, het tot mengsels van produkte aanleiding gegee. Enkelkristalle van komplekse [Ph3PCH(AuC6F5)C6H4CH3] (14), [C6F5Au(tht)] (15) en [(C6F5)2Au][(Ph3PCH2)2C6H4] (16) is geïsoleer uit die reaksies en kristalstruktuurbepalings is uitgevoer. Die molekulere struktuur van 15 toon ongewone aurofiliese interaksies en verteenwoordig die eerste voorbeeld van ʼn linieêre goudketting; met goud···goud afstande wat sistematies varieër tussen 3.13Å, 3.31Å en 3.20Å. Sout 2b is met Ph3PAu(acac) gereageer om die gewenste produk, [{Ph3PCH(AuPPh3)}2CH2](BF4)2 (19), saam met [CH3C(O)C(AuPPh3)2C(O)CH3] (17) en ander byprodukte te vorm. Verbinding 17 is as enkelkristalle Xstraalkristallografies gekarakteriseer. Die fluorobifeniel goud(I)-komplekse, 4,4’-[(AuPPh3)2C12F8] (21) en 2,2’- [(AuPPh3)2C12F8] (22), is gesintetiseer deur koördinasie van AuPPh3 aan die gelitieërde 2,2’-dibromooktafluorobifeniel en 4,4’-dibromooktafluorobifeniel respektiewelik. Die molekulere struktuur van 21 het getoon dat een van die C-Au- P bindingshoeke met 12.5º afwyk van 180º, waarskynlik as gevolg van π- interaksie van die tetrafluorofenielringe en die steriese vereistes van die groot PPh3-eenhede. Die ander C-Au-P bindingshoek is linieêr [177.9(3)°].

Thesis (MSc)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: This study comprises the synthesis and full characterization of two novel pendant-arm donor macrocyclic ligands. The stability and structure of the complexes of these two ligands with a series of metals ions [Mn(II), Co(II), Zn(II), Cd(II), Pb(II)], was subsequently investigated. The two parent macrocyclic ligands, 1,4,7-triazacyclodecane ([10]-ane-N3) and 1,4,8- triazacycloundecane ([11]-ane-N3) were synthesized by means of the "direct synthesis" method using tosylates as protecting groups. Pendant arms were then added to the parent molecules to create hexadentate ligands. The two macrocyclic ligands are asymmetric because of the different lengths of the carbon bridges between the N-donor atoms of the rings. This feature gives the ligands the possibility to form both five- and six-membered rings when coordinated to metal centers. The ligands were fully characterized by means of NMR, mass spectrometry and elementalanalysis. Melting points were also determined. These two novel (triaza macrocyclic) ligands now complete the series between 9-ane- N3 [with its 2-(S)-hydroxypropyl pendant arms] and 12-ane-N3 [with its 2-(S)- hydroxypropyl pendant arms]. Protonation data of the ligands were determined using potentiometric titrations. The respective protonation constants for both ligands in 0.1000 mol dm-3 NaNO3 are: THTD log H 1 K = 9.176 and log H 2 K = 4.20 THTUD log H 1 K = 11.32 and log H 2 K = 5.87 A third protonation constant for both ligands (THTD and THTUD) was observed, but the use of potentiometric methods could not produce reliable values at very low pH values. stability constants of the new ligands with a series of metal ions were determined using 0.1000 mol dm-3 NaNO3 as ionic medium. The log(K) values at 25°C with THTD are: Co(II) 22.93 Zn(II) 14.82 Cd(II) 19.38 Pb(II) 15.47 The log(K) values at 25°C with THTUD are: Co(II) 17.52 Zn(II) 16.43 Cd(II) 18.05 Pb(II) 14.63 Very stable complexes were obtained with the larger Cd(II) ion when compared to other similar ligands. Crystal structures of some of the metal complexes were determined by X-ray crystallography. Metal perchlorates were used in the preparation of the metal complexes with THTD and THTUD, and various methods were utilized for the crystallization process. The general formula for these complexes is [M(L)]2+·2(ClO4)- where M=metal ion and L= neutral ligand. The bond lengths between the nitrogen atom and the metal ion, and the oxygen atom and the metal ion are very much the same in the respective crystal structures. This means that the metal ion lies almost halfway between the nitrogen and the oxygen atoms. The Mn(II)-THTD complex featured both a distorted octahedral and distorted trigonal prismatic configuration in the unit cell. Co(II)-THTUD contains three molecules per unit cell all having a distorted octahedral configuration. Zn(II)-THTUD crystallizes with six molecules per unit cell. / AFRIKAANSE OPSOMMING: Hierdie studie behels die bereiding en volledige karakterisering van twee oorspronklike hangkroonarmdonor makrosikliese ligande. Die stabiliteite en struktuur van komplekse van hierdie twee ligande met ’n reeks metaalione [Mn(II), Co(II), Zn(II), Cd(II), Pb(II)] is ondersoek. Die twee basis ligande 1,4,7-triazasiklodekaan (10-ane-N3) en 1,4,8-triazasikloundekaan (11- ane-N3) is gesintetiseer deur middel van die "direkte bereidingsmetode" met tosilate as beskermingsgroepe. Hangkroonsyarms is aangeheg om die vorming van ’n heksadentate ligand te bewerkstellig. Die twee makrosikliese ligande is asimmetries as gevolg van die verskillende lengtes van die koolstofbrûe tussen die N-donor atome van die ringe. Hierdie eienskap gee aan die ligande die vermoë om beide vyf- en seslidringe te vorm wanneer komplekse gevorm word met metaalione. Die ligande is ten volle gekarakteriseer deur middel van KMR-metings, massa-spektroskopie en element analise. Smeltpuntbepalings is ook uitgevoer. Die twee nuwe ligande voltooi nou die homoloë reeks tussen 9-ane-N3 [en sy 2-(S)- hidroksiepropiel hangkroonarms] en 12-ane-N3 [en sy 2-(S)-hidroksiepropiel hangkroonarms]. Protonasiedata van die ligande is bepaal deur middel van potensiometriese titrasie. Die onderskeie protonasiekonstantes vir beide ligande in 0.1000 mol dm-3 NaNO3 is: THTD log H 1 K = 9.176 en log H 2 K = 4.20 THTUD log H 1 K = 11.32 en log H 2 K = 5.87 ’n Duidelik-waarneembare derde protonasiekonstante vir beide ligande (THTD en THTUD) is opgemerk, maar potentiometriese metodes kon nie betroubare waardes lewer by die uiters lae pH-lesings nie. Vormingskonstantes van die ligande met ’n reeks oorgangsmetale is bepaal deur gebruik te maak van ’n 0.1000 mol dm-3 NaNO3 as ioniese medium. Die log(K) waardes by 25°C vir THTD is: Co(II) 22.93 Zn(II) 14.82 Cd(II) 19.38 Pb(II) 15.47 Die log(K) waardes by 25°C met THTUD is: Co(II) 17.52 Zn(II) 16.43 Cd(II) 18.05 Pb(II) 14.63 Uiters stabiele komplekse is verkry met die groter Cd(II) ioon in vergelyking met ander soortgelyke ligande. Kristalstrukture van sommige van die metaalkomplekse is bepaal deur middel van X-straal kristallografie. Metaalperchlorate is gebruik om metal komplekse met THTD en THTUD te berei, en ’n verskeidenheid kristallisasieprosesse is gebruik. Die algemene formule vir hierdie komplekse is [M(L)]2+·2(ClO4)- waar M = metaal ioon en L = neutrale ligand is. Die bindingslengtes tussen die stikstof atoom en die metaalioon, en die suurstof atoom en die metaalioon is nagenoeg dieselfde in die onderskeie kristalstukture. Dit beteken dat die metaalioon ongeveer halfpad tussen die stikstof en die suurstof atome voorkom. Die Mn(II)- THTD-kompleks vertoon beide oktahedrale - en trigonaal prismatiese konfigurasie in die eenheidsel. Co(II)-THTUD het drie molekule per eenheidsel, almal verwronge oktahedrale konformasies. Zn(II)-THTUD het gekristaliseer met ses molekule per eenheidsel.

Thesis (MSc)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Quantum mechanics is the method of choice when it comes to the accurate modeling of single molecules and clusters. The correlation energy is the single most important aspect when studying clusters computationally, and reproducing the correlation energy accurately poses a bigger challenge to the computational chemist than in the modeling of single molecules. Very high levels of theory and large basis sets need to be used. Nevertheless, since the calculation of large systems, such as crystals and biological systems, is generally beyond the capacity of quantum mechanics, molecular mechanics is generally used for these systems. Unfortunately due to its nature, molecular mechanics cannot model important quantum effects, but this problem can be solved by a hybrid system in which one part of the system is treated by quantum mechanics and the remaining part by molecular mechanics. In order to combine quantum mechanics with molecular mechanics one needs to optimize the parameters for the molecular mechanics part to allow it to function with the quantum mechanics. The research described in this work is based on the ONIOM-EE method, which is such a hybrid method. In this work we investigate the applicability of the ONIOM-EE method in modeling hydrogen fluoride, carbon monoxide and CO/HF clusters. Most of the clusters’ geometries in this work are not experimentally or computationally known. We therefore perform a computational analysis of all of the clusters by using various methods including Atoms in Molecules, Natural Bond Orbital analysis, Mulliken population analysis and the analysis of delocalized molecular orbitals to obtain information for the development of hybrid systems. During this process we look at different charge derivation schemes and at two different methods of optimizing force field parameters for these clusters. We develop a method to make force field optimization faster and better for specific hybrid systems. This method showed that in all cases the optimized parameters were an improvement on those of the Universal Force Field. We show the importance of an accurate description of the electrostatic interactions in HF, CO and CO/HF clusters and that this is the Achilles heel when attempting to optimize van der Waals parameters for force fields. We further show that atomic point charges are not a good approximation of a molecules’ charge density in hybrid methods. In addition, we make suggestions on how the present method for ONIOM-EE can be improved to make the modeling of van der Waals clusters feasible. / AFRIKAANSE OPSOMMING: Kwantum meganika is die metode van keuse wanneer enkele molekule en molekulêre sisteme op rekenaar gemodeleer moet word. Dit is egter bekend dat die modelering van molekulêre sisteme ’n groter uitdaging stel aan die molekulêre modeleerder, aangesien baie hoë vlakke van teorie en groot basisstelle gebruik moet word om die korrelasie-energie, rekenkundig te produseer. Die akkurate herprodusering van die korrelasie-energie is seker die heel belangrikste vereiste waaraan voldoen moet word as molekulêre sisteme d.m.v. ’n rekenaar gemodeleer word. Nietemin is dit onprakties om kwantum meganiese metodes te gebruik vir groot sisteme soos kristalle of biologiese molekule en juis om dié rede word molekulêre meganika meestal ingespan vir sulke gevalle. Molekulêre meganika is egter ondoeltreffend om belangrike kwantumeffekte te modeleer. Tog is daar ’n oplossing vir hierdie probleem in die vorm van ’n hibried sisteem waar een deel van die sisteem met kwantum meganika en die oorblywende deel van die sisteem met molekulêre meganika behandel word. Om dit moontlik te maak om molekulêre meganika met kwantum meganika te kombineer, moet parameters vir die molekulêre meganika deel geoptimiseer word sodat dit saam met die kwantum meganiese deel kan funksioneer. Die navorsing wat in hierdie studie beskryf word is gebaseer op so ’n hibriedmetode wat bekend staan as ONIOM-EE. In hierdie studie bestudeer ons die moontlikheid om ONIOM-EE te gebruik vir die modelering van molekulêre sisteme van waterstoffluoried, koolstofmonoksied en CO/HF sisteme. Die meeste van die sisteme, wat in hierdie studie behandel word, se strukture is onbekend, beide in terme van eksperimentele gegewens en molekulêre modelering. Ons voer dus ’n volledige analise van al die sisteme uit deur van verskeie metodes soos “Atoms in Molecules”, “Natural Bond Orbital” analise, Mulliken populasie analise en die analise van gedelokaliseerde molekulêre orbitale, gebruik te maak. Dit stel ons in staat om ’n hibriedsisteem te ontwikkel vir die molekulêre sisteme. Gedurende die proses ondersoek ons ook die gebruik van verskillende ladingsafleidings-sisteme en twee metodes word ondersoek waarop ’n kragveld vir ’n hibriedsisteem geoptimiseer kan word. Ons toon aan dat die geoptimiseerde parameters beter resultate lewer as die van die “Universal Force Field” en lig ook die belangrikheid daarvan uit dat die elektrostatiese interaksies se beskrywing ’n hibriedsisteem se Achilles hiel is indien van der Waals parameters geoptimiseer moet word. Ons toon aan dat die gebruik van puntladings op atome om die ladingsdigtheid in molekulêre sisteme te beskryf, ’n onakkurate benadering is. Sekere aanbevelings hoe om die ONIOM-EE metode sodanig te verbeter, dat dit wel gebruik kan word om van der Waals sisteme suksesvol te modeleer, word ook gemaak.

Thesis (MSc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: This study comprises the preparation and characterization of various novel organometallic complexes of palladium(ll) which contain symmetric and unsymmetric (heteroatom-containing) r..-dicarbonyl-type ligands, T]3-heteroallyl ligands and T]3-coordinated trimethylsilyl-containing ligands. With the ultimate objective of preparing potential catalytic precursors similar to known catalytic precursors which exhibit hemilabile activity, the main goals of this study were the following: - • Investigate the coordination mode of the aforementioned ligand-types to the palladium of the starting compound, trans-[Pd(CeHs)CI{P(CeHshhl (1), by physical measurements. • Carry out single crystal structure determinations where possible. • Investigate the influence of the properties of the ligands on the stability of the prepared complexes. • Investigate the existence of hemilability (if any) in the prepared complex. The deprotonated symmetric and unsymmetric f!,-dicarbonyl-type ligands readily bind to the palladium of the starting compound in a bidentate fashion through the oxygens by displacing a triphenylphosphine group and producing easily removable sodium chloride. These complexes show that a negative charge can be accommodated in a delocalized fashion by the -S=O and - P=O groups of these acac--type ligands in a similar manner to the carbonyl groups of acetylacetonate. However, no evidence of hemilabile activity was found in this series of complexes. In a similar fashion, the deprotonated T]3-heteroallyl ligands, L = [PhzPS£], [PhCOz-], [PhC{NSi(CH3hhl [(Ph)zP{NSi(CH3hh-], were linked to palladium in the same starting complex, in T]3-fashion by triphenylphosphine substitution. No evidence of hemilabilty was evident in this series of complexes, but when L = [PhzPSz-], an exchange of the coordinated triphenylphosphine group with the free triphenylphosphine group was observed in the reaction mixture. Finally, the preparation, isolation and spectroscopic characterization of several T\3-allyl paliadium(lI) complexes with ligands of the type R-TeCH2CH2CQQCH3, (R = isopropyl, t-butyl ,ethyl) were attempted with the compound bis-( T\3-allyl )-di-~ -iodo-dipalladium( II), [T\3 -( CH2CHCH2J2Pd212J, which had also now been crystallographically characterized. Chelate formation by TeAQ coordination seemed possible by halide precipitation with silver tetrafluoroborate. Unfortunately the resulting compounds were too unstable to be isolated in the pure form for characterization. / AFRIKAANSE OPSOMMING: Die studie behels die bereiding en karakterisering van verskeie nuwe palladium(lI) organometaalkomplekse met inbegrip van simmetriese en onsimmetriese (heteroatoom bevattende) ~-dikarboniel-tipe ligande, 113- heteroallielligande en 113_gekoordineerdetrimetielsiliel bevattende ligande. Met die beoogde einddoel die bereiding van potensiele katalitiese voorgangers soortgelyk aan bekende katalitiese voorgangers met hemilabiele aktiviteit, sluit die hoof mikpunte van die studie die volgende in: - • 'n Ondersoek na koordinasie-wyse van die bogenoemde ligand tipes aan die palladium van die uitgangstof, trans-[Pd(C6Hs)CI{P(C6Hshhl (1), met behulp van fisiese bepalings. • Enkel kristal struktuur bepalings waar moontlike. • 'n Ondersoek na die invloed van die einskappe van die ligande op die stabilitiet van die komplekse. • 'n Ondersoek na die bestaan van hemilabiele aktiwiteit (indien enige) in die voorbereide complekse. Die gedeprotoneerde simmetriese en onsimmetriese ~-dikarboniel-tipe ligande het geredelik, bidentaat deur middel van die suurstowwe gebind aan die palladium van die uitgangstof deur die verplasing van die trifenielfosfien group en die vorming van verweiderbare natriumchloried. Hierdie komplekse dui aan dat 'n negatiewe lading wei geakkommodeer kan word deur delokalisasie by die -S=O- en -P=O-groepe van hierdie acac"-tipe Iigande, soortgelyk aan die karbonielgroep van asetielasetonaat. Geen hemilabiliteit is waargeneem in hierdie reeks komplekse nie. Die gedeprotoneerde 113-heteroalliel Iigande, L = [Ph2PS£), [PhCO£), [PhC{NSi(CH3h}£), [(PhhP{NSi(CH3hhl is op 'n soortgelyke wyse 113- gekoppel aan palladium van dieselfde uitgangstof met trifenielfosfien verplasing. Geen hemilabiliteit is waargeneem in hierdie reeks komplekse nie, maar wanneer L = [Ph2PS£], is 'n uitruiling van 'n gekoordineerde trifenielfosfien met 'n vrye trifenielfosfien in die reaksiemengsel waargeneem. Die bereiding, isolasie en spektroskopiese karakterisering van Tj3-alliel paliadium(lI) komplekse met ligande van die tipe R-TeCH2CH2COOCH3, (R = isopropiel, t-butiel ,etiel) is gepoog met die uitgangstof bis-(Tj3-alliel)-di-ll-iododipaliadium( II), [Tj3-(CH2CHCH2hPd2b], wat volledig gekarakteriseer was. Chelaat-vorming deur TeAO-koordinasie het moonlik blyk te wees deur halied presipitasie met behulp van AgBF4. Die komplekse is baie onstabiel en is dit gevolglik nie moontlik am die komplekse suiwer te isoleer en te karakteriseer nie.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The separation of apple, cocoa and green tea phenolic compounds by comprehensive 2-dimensional liquid chromatography (2-D-LC) has been studied. In the first dimension, phenolic compounds were separated according to polarity by hydrophilic interaction chromatography (HILIC) on a diol stationary phase with a mobile phase containing acetonitrile, methanol, acetic acid and water. Gradient reversed-phase (RP) LC using a C18 column with fluorescence detection was employed in the second dimension to separate compounds according to hydrophobicity. Compounds were identified using negative electrospray ionisation mass spectrometry (ESI-MS) coupled to both HILIC and RP separations. The coupling of HILIC and RP separations proved to be especially beneficial since this provided simultaneous information on both the polarity and hydrophobicity of phenolics. The low degree of correlation (r2 < 0.21) between the two LC modes afforded peak capacities in excess of 3000 for the off-line method. An on-line method was also developed utilizing a short, small particle-packed column to provide fast separation in the second dimension. A 1 mm i.d. column was used in the first dimension for the on-line system to reduce injection volumes onto the second dimension column. A significantly lower practical peak capacity was measured for the on-line system, due largely to the reduction in second dimension peak capacity. On the other hand, analysis could be performed in an automated fashion using the online system reducing the risk of sample alteration and guaranteeing better operation reliability and reproducibility. Especially the off-line comprehensive HILIC × RP-LC method developed demonstrated its utility in the analysis of various groups of phenolic compounds including proanthocyanidins, phenolic acids, flavonols and flavonol conjugates in a variety of natural products. / AFRIKAANSE OPSOMMING: Die skeiding van fenoliese komponente in appel, kakao en groen tee is deur middel van ‘comprehensive’ 2-dimensionele vloeistof chromatografie (2-D-LC) bestudeer. Hidrofiliese interaksie chromatografie (HILIC) is gebruik om die fenoliese komponente in die eerste dimensie te skei op grond van polariteit, deur gebruik te maak van ‘n diol stationêre fase en mobiele fase bestaande uit asetonitriel, metanol, asynsuur en water. ‘n Gradiënt omgekeerde fase (RP) LC analisie op ‘n C18 kolom met fluorosensie deteksie is in die tweede dimensie gebruik om fenole volgens hidrofobisiteit te skei. Negatiewe elektrosproei-ionisasie massa spektometrie (ESIMS) gekoppel aan HILIC en RP skeidings is gebruik vir identifikasie van fenole. Die koppeling van HILIC en RP skeidings veral voordelig deurdat dit gelyktydige informasie verskaf het oor die polariteit sowel as die hidrofobisiteit van die fenoliese komponente. Die lae graad van korrelasie (r2 < 0.21) tussen die twee LC metodes was verantwoordelik vir piek kapasiteite bo 3000 vir die af-lyn metode. ‘n Aanlyn metode was ontwikkel deur gebruik te maak van ‘n kort, klein partikel gepakte kolom om vinnige skeiding in die tweede dimensie te verseker. 1 mm i.d. kolom was gebruik in die eerste dimensie vir die aanlyn sisteem om die inspuit volume op die tweede dimensie kolom te verminder. Aansienlike laer praktiese piek kapasiteit was gemeet vir die aanlyn sisteem, grootliks toegeskryf aan die reduksie in die tweede dimensie piek kapasitiet. Aan die ander kant, analise kan geoutomatiseerd uitgevoer word deur gebruik te maak van die aanlyn sisteem, wat monster alterasie, beter betroubaarheid en reproduseerbaarhied verseker. Veral die ontwikkelde af-lyn ‘comprehensive’ HILIC × RP-LC metode toon demonstreerbare voordele vir die analiese van verskeie groepe fenoliese komponente, insluitende proantosianiede, fenoliese sure, flavonole en gekonjugeerde flavonole in ‘n verskeidenheid natuurlike produkte.