Nuclear Magnetic Resonance (NMR) spectroscopy is a quantitative, non-invasive and non-destructive technique useful in biological studies. By manipulating the magnetization of nuclei with non-zero spin, NMR gives insights into atomic level details. Application of NMR as a tool for discovering structure, understanding dynamics of bio-molecules such as proteins, metabolites, DNA, RNA and their interactions constitutes the field of bio-molecular NMR. In this thesis, new methods for rapid data analysis of NMR spectrum of proteins and metabolites are proposed. The first computational method, PROMEB (Pattern Recognition Based Assignment in Metabolomics) is useful for the identification and assignments of metabolites. This is an important step in metabolomics and is necessary for the discovery of new biomarkers. In NMR spectroscopy based studies, the conventional approach involves a database search, wherein chemical shifts are assigned to specific metabolites by use of a tolerance limit. This is inefficient because deviation in chemical shifts associated with pH or temperature variations, as well as missing peaks, impairs a robust comparison with the database. These drawbacks are overcome in PROMEB, which is a method based on matching the pattern of peaks of a metabolite in 2D [13C, 1H] HSQC NMR spectrum, rather than conventionally used absolute tolerance thresholds. A high success rate is obtained even in the presence of large chemical shift deviations such as 0.5 ppm in 1H and 3 ppm in 13C and missing peaks (up to 50%), compared to nearly no assignments obtained under these conditions with existing methods that employ a direct database search approach. The pattern recognition approach thus helps in identification and assignment of metabolites in-dependent of the pH, temperature, and ionic strength used, thereby obviating the need for spectral calibration with internal or external standards. Another computational method, ChemSMP(Chemical Shifts to Metabolic Path-ways), is described which facilitates the identification of metabolic pathways from a single two dimensional (2D) NMR spectrum. Typically in other approaches, this is done after relevant metabolites are identified to allow their mapping onto specific metabolic pathways. This task is daunting due to the complex nature of cellular processes and the difficulty in establishing the identity of individual metabolites. ChemSMP uses a novel indexing and scoring system comprised of a uniqueness score and a coverage score. Benchmarks show that ChemSMP has a positive prediction rate of > 90% in the presence of decluttered data and can sustain the same at 60 − 70% even in the presence of noise, such as deletions of peaks and chemical shift deviations. The method tested on NMR data acquired for a mixture of 20 amino acids shows a success rate of 93% in correct recovery of metabolic pathways. The third method developed is a new approach for rapid resonance assignments in proteins based on amino acid selective unlabeling. The method involves choosing a set of multiple amino acid types for selective unlabeling and identifying specific tripeptides surrounding the labeled residues from specific 2D NMR spectra in a combinatorial manner. The methodology directly yields sequence specific resonance assignments, without requiring a contiguously assigned stretch of amino acid residues to be linked, and is applicable to deuterated proteins. The fourth method involves a simple approach to rapidly identify amino acid types in proteins from a 2D NMR spectrum. The method is based on the fact that 13Cβ chemical shifts of different amino acid types fall in distinct spectral regions. By evolving the 13C chemical shifts in the conventional HNCACB or HN(CO)CACB type experiment for a single specified delay period, the phase of the cross peaks of different amino acid residues are modulated depending on their 13Cβ chemical shift values. Following this specified evolution period, the 2D HN projections of these experiments are acquired. The 13C evolution period can be chosen such that all residues belonging to a given set of amino acid types have the same phase pattern (positive or negative) facilitating their identification. This approach does not re-quire the preparation of any additional samples, involves the analysis of 2D [15N,1H] HSQC-type spectra obtained from the routinely used triple resonance experiments with minor modifications, and is applicable to deuterated proteins. Finally, the practical application of these methods for laboratory research is presented. PROMEB and ChemSMP is used to study cancer cell metabolism in previously unexplored oncogenic cell line. PROMEB helped in assigning a differential metabolite present at high concentration in cancer cell line compared to control non-cancerous cell line. ChemSMP revealed active metabolic pathways responsible for regulating energy homeostasis of cancer cells which were previously reported in literature. The two methods developed for rapid protein resonance assignments can be used in applications such as identifying active-site residues involved in ligand binding, phosphorylation, or protein-protein interactions. The phase modulated experiments will be useful for quick assignment of signals that shift during ligand binding or in combination with selective labeling/unlabeling approaches for identification of amino acid types to aid the sequential assignment process. Both the methodology was applied to two proteins: Ubiquitin (8 kDa) and L-IGFBP2 an intrinsically disordered protein (12 kDa), for demonstrating rapid resonance assignment using only set of 2D NMR experiments.

Linseed oil has been and is used for vast number of applications, such as in food and paint industry, and wood preservation. It is a good environmental choice, as it originates from renewable sources. Linseed oil is mainly a mixture of triglyceride of fatty acids, both saturated and mono- or polyunsaturated, which allows the oil to oxidize. The oxidation occurs via an auto-oxidation mechanism with the carbon-carbon double bonds and oxygen from the air, reacts to form a polymer. Herein, four different linseed oils (three commercial ones and one industrially available) were analyzed to obtain a better understanding of why different oils provide different protection of wooden materials. This was done by a study of the unoxidized oil, followed by an oxidation time-resolved study of oxidized oil films. The analysis was done by nuclear magnetic resonance, gas chromatography - mass spectrometry and/or inductively coupled plasma atomic emission spectroscopy. This study provided the fatty acid profile of the oils, which were similar for all oils. The unoxidized oils contained some metals ions which probably originate from additives. Aluminum, cobalt, iron, manganese, and zinc was detected in some of the oils at concentrations up to 135 mg/L, but only manganese was detected in all oils and its concentration was much higher than all other metals together. The time-resolved oxidation study had some problems with the solubility of the formed polymers. Several solvents were examined, such as dimethylsulfoxide, alkaline alcohol solutions and toluene, before chloroform-d was chosen as solvent. Though, chloroform-d was not a perfect solvent; it was capable to solve a fraction of the sample, but the fraction decreased with oxidation time. After fifteen days of oxidation, only a few percent of the sample could be dissolved, but for short oxidation times (<48 h) the majority of the samples were dissolved. The oils were analyzed after thirteen different oxidation times. Some structural changes appeared, for example loss of unsaturated protons and some oxidation products arose, such as peroxides and aldyhydes. The diffusion coefficient decreased over the first 3-4 days of oxidation, as expected when the polymerization progressed. After a week of oxidation, the diffusion coefficient increased again, this could possibly be explained by the solubility problem for the large polymer formed. Contrary, at shorter oxidation times this method probably could still be used, as the majority of the sample was dissolved. However, the solubility problem made it impossible to conclude anything about the oxidation rate at longer oxidation times and thus prevented any ranking of the oils. / Linolja har använts och används för många olika tillämpningar, till exempel i mat- och färgindustrin, samt för att bevara trä. Det är klimatmässigt ett bra val, då det kommer från en förnyelsebar källa. Linolja innehåller huvudsakligen en blandning av triglycerider av fettsyror, som både kan vara mättade, enkelomättade eller fleromättade, detta gör att linolja kan oxidera och torka. Oxidationen sker via en auto-oxidation mekanism, med kol-kol dubbelbindningarna och syre från luften som producerar till en polymer. I detta projekt undersöktes fyra olika linoljor (tre kommersiella och en industriell), för att ge en bättre förståelse till varför olika oljor ger olika bra skydd för trämaterial. Detta gjordes genom att undersöka de icke-oxiderade oljorna och sedan göra en tidsstudie på oxiderade oljefilmer. Alla dessa prover analyserades med nuclear magnetic resonance, gas chromatography - mass spectrometry and/or inductively coupled plasma atomic emission spectroscopy. Studien gav resultat på sammansättningen av fettsyror i oljorna, vilken var liknande för alla oljorna. De icke-oxiderade oljorna innehöll ett par metaller, som förmodligen kommer från additiv. Aluminium, kobolt, järn, mangan och zink hittades i några av oljorna i koncentrationer upp till 135 mg/L, men bara mangan var detekterad i alla oljorna och dess koncentration var högre än alla andra metaller tillsammans. Tidsstudien hade problem med lösligheten av proverna. Flertalet lösningsmedel undersöktes, exempelvis dimetylsulfoxid, alkaliska alkohollösningar och toluen, innan kloroform-d valdes som lösningsmedel. Däremot var kloroform-d inte ett perfekt lösningsmedel, den hade förmågan att lösa en del av proverna, men den delen minskade med oxidationstid. Efter femton dagar kunde den bara lösa ett par procent, men efter kortare oxideringstider (<48 h) gick majoriteten av proven att lösa. Oljorna analyserades vid tretton olika oxideringstider. Några strukturella förändringar uppmättes, till exempel minskade mängden dubbelbindningar, och ett par biprodukter från oxideringen detekterades, så som peroxider och aldehyder. Diffusionskonstanterna för oljorna minskade under de första 3-4 dagarna av oxidering, precis som förväntat under polymeriseringen. Efter en vecka av oxidering ökade diffusionskonstanterna igen, det kan förmodligen förklaras av löslighetsproblemen, då diffusionskonstanten är beroende av koncentrationen. Å andra sidan, vid kortare oxideringstider kan denna metod fortfarande användas, eftersom vid denna tidpunkt löste sig fortfarande majoriteten av provet. Dock, löslighetsproblemet gjorde det omöjligt att dra slutsatser kring längre oxideringstider och därmed förhindrades rangordning av oljorna.

Nuclear Magnetic Resonance (NMR) and computational methods increasingly play a predominant and indispensable role in modern chemical research. The insights into the local nuclear environment that NMR can provide is unique information which allows the structural characterization of novel materials, as well as the understanding and explanation of their relevant properties on an atomic scale. Computational methods, on the other hand, can be used to support experimental findings, providing a rigorous theoretical basis. Furthermore, when more complex chemical systems are considered, calculations can prove to be invaluable for the interpretation of experimental data and often allow an otherwise impossible spectral assignment. This thesis presents a series of studies in which NMR spectroscopy, in combination with computational methods, is utilized to investigate a variety of chemical systems both in solution and the solid state. An overview of the thesis and experimental and computational details are given in Chapter 1. In Chapter 2, the quantum mechanical basis necessary for the description of the NMR phenomenon is presented. Chapter 3 explores the main experimental techniques employed routinely for the acquisition of NMR spectra in both solution and the solid state. Chapter 4 describes the main features of density functional theory (DFT) and its implementation in computational methods for the calculation of relevant NMR parameters. Chapter 5 reports an experimental solution-phase NMR study and a parallel computational investigation of the poly(CTFE-co-EVE) fluoropolymer. In Chapter 6, the combination of [superscript(14/15)]N solution-phase NMR techniques and DFT methods for the study of alkylammonium cationic templates used in the synthesis of microporous materials is presented. The characterization of a boroxoaromatic compound in the solid state and the study of its reactivity are described in Chapter 7. In Chapter 8, two experimental NMR methods for the study of the anisotropic chemical shift interaction in the solid state are compared and used to characterize a range of materials. Cross-polarization and nutation of quadrupolar nuclei are computationally investigated under both static and spinning conditions in Chapter 9. A general conclusion and a summary are given in Chapter 10.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / Please refer to full text for abstract. Abstract contains special characters.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / This thesis begins with the description of the preparation of thirteen dithioesters (of the form Z- (C=S)-S-R) which were characterized via Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR) and ultraviolet spectroscopy (UV). The dithioesters were then used as reversible addition-fragmentation chain transfer (RAFT) mediating agents in the bulk polymerization of styrene, in order to observe differences in the kinetic behaviour of the polymerizations and, as a result, the efficiencies of the dithioesters in mediating the polymerizations.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Due to the commercial, nutritional and health value of vegetable oils, seeds and beans, the analysis of their components is of much interest. In this dissertation oil-containing food products, specifically vegetable oils, seeds and beans, were investigated. Selected minor components of three locally produced vegetable oils, namely apricot kernel, avocado pear and macadamia nut oils were investigated using 31P NMR spectroscopy. These minor components, including 1,2 diacylglycerols, 1,3 diacylglycerols and free fatty acids, were identified in the 31P NMR spectra of each of the three vegetable oils for the first time. Two approaches were used for the quantification of the minor components present in the spectra. A calibration curve approach used known concentrations of standard minor components to establish calibration curves while a direct correlation approach calculated the unknown concentration of minor components in the vegetable oils using a known amount of standard compound within the analysis solution. These approaches aided in determining the concentration of minor components during storage studies in which vegetable oils were stored in five different ways: exposed to light, in a cupboard, in a cupboard wrapped in tin foil, at -8 °C and at 5 °C. It was found that determining the best storage condition for each oil was difficult since individual minor components were affected differently by the various storage conditions. However, in general the best storage conditions appeared to be 5 °C and -8 °C. The oil, protein and carbohydrate contents of sesame, sunflower, poppy, and pumpkin seeds, and soy, mung, black and kidney beans were analysed by thermogravimetric analysis and 13C NMR solid state NMR spectroscopy. It was shown that the first derivative of TGA data for seeds and beans can give valuable information about the carbohydrate, moisture, protein and fat content. This has not been previously demonstrated. For the seeds, the integration of a region between 270–480 ºC was equal to the sum of the oil and protein content and compared well to quantitative results obtained by other conventional methods. For beans the integration of a region between 180-590 ºC, gave a value which represented the sum of the oil, protein and carbohydrate content. 13C solid state NMR spectroscopy, including SPE-MAS, CP-MAS and variable contact time experiments, was carried out on these seeds and beans and gave valuable information on the solid-like and liquid-like components. To our knowledge these seeds and beans have never been previously analysed using this technique. 13C SPE-MAS NMR spectroscopy indicated that the seeds contained more liquid-like components than the beans. In turn the 13C CP-MAS NMR spectra indicated that beans had higher levels of solid-like components than the seeds. These conclusions correlated well with the quantities of liquid-like components and solid-like components that were determined by conventional methods and TGA. Preliminary studies using T1pH experiments on the components present in the seeds and beans led to a few observations. Most interesting is that a model using a two- phase fit in order to determine T1pH values appears to be more accurate than a one-phase model. / AFRIKAANSE OPSOMMING: Groente olies, sade en bone is ‘n onderwerp van groot belang omrede hul kommersiële, voeding en gesondheidswaardes. In hierdie tesis is olie-bevattende voedselprodukte, spesifiek groente-olies, sade en bone geanaliseer. Geselekteerde komponente teenwoordig in klein hoeveelhede in drie lokaal geproduseerde groente-olies, naamlik appelkoos-pit, avokadopeer en makadamia-neut olies is geanaliseer met behulp van 31P KMR spektroskopie. Hierdie komponente, insluitend 1,2 diasielglyserole, 1,3 diasielglyserole en ongebonde vetsure, is vir die eerste keer geïdentifiseer in die 31P KMR spektra van die drie groente olies. Twee benaderings is gebruik vir die hoeveelheids-bepaling van die komponente in die spektra. ‘n Yking-kurwe metode het gebruik gemaak van bekende hoeveelhede konsentrasies standaard komponente vir die opstel van yking-kurwes, terwyl ‘n direkte korrelasie metode gebruik is om die onbekende konsentrasie van komponente in groente olies te bepaal met behulp van ‘n bekende hoeveelheid standaard verbinding teenwoordig in die oplossing. Hierdie metodes het gelei tot die bepaling van die konsentrasies van die komponente gedurende vyf verskillende berging toestande wat ingesluit het: Blootgestel aan lig, in ‘n donker kas, in ‘n donker kas toegevou in tin foelie, bevries by -8 °C en in ’n koelkas by 5 °C. Dit was bevind dat bepaling van die beste bergingstoestand vir elke olie moeilik is aangesien die individuele komponente verskillend geaffekteer word deur die verskeie berging toestande. Die beste bergings toestand oor die algemeen blyk egter om by 5 °C en -8 °C te wees. Sesamsaad, sonneblomsaad, papawersaad en pampoensaad sowel as sojaboontjie, mungboontjie, swartboontjie en pronkboontjie se olie, protein en koolhidraat komponente was geanaliseer met behulp van termogravimetriese analise (TGA) en 13C soliede toestand KMR spektroskopie. Dit was bevind dat die eerste afgeleide van die TGA data waardevolle inligting lewer oor die komponent inhoud van elk van die sade en bone. Hierdie is nog nie vantevore bevind nie. Vir die sade, was die integrasie van ‘n area tussen 270–480 ºC gelyk aan die som van die olie en proteïen inhoud en het goed vergelyk met die waardes verky deur algemene analitiese metodes. Vir die boontjies, was die integrasie van ‘n area tussen 180-590 ºC gelyk aan die som van die olie, protein en koolhidraat inhoud. 13C vaste staat KMR spektroskopie, insluitende SPE-MAS, CP-MAS en variëerbare kontak-tyd eksperimente, was gedoen en het waardevolle inligting gelewer omtrent die solied-agtige en mobiel-agtige komponente. Hierdie sade en bone is tot ons kennis nog nie van te vore met die tegnieke ondersoek nie. 13C SPE-MAS NMR spektroskopie het aangedui dat daar ‘n groter hoeveelheid mobiel-agtige komponente in sade as in bone teenwoordig is. 13C CP-MAS NMR spektroskopie het weer aangedui dat daar ‘n groter hoeveelheid solied-agtige komponente in bone as in sade teenwoordig is. Hierdie gevolgtrekkings het goed vergelyk met die waarnemings verkry deur konvensionele analitiese metodes en TGA. Voorlopige studies op die komponente van sade en bone deur T1pH eksperimente het tot ‘n paar gevolgtrekkings gelei waarvan die mees interessantste was dat ‘n twee-fase model vir die bepaling van T1pH waardes beter resultate lewer as ‘n een-fase model.

Thesis (PhD)--Stellenbosch University, 2012. / See full text for abstract. / Sien volteks vir opsomming

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In this thesis, the recovery of RhIII from both synthetically prepared and authentic industrial PGM-containing solutions was systematically investigated via organic precipitation methods using several commercially available, N-containing organic receptors including (amongst others) diethylenetriamine (Deta), triethylenetetramine (Teta), tetraethylenepentamine (Tepa) and tris(2-aminoethyl)amine (Tren). These organic receptors act as precipitating agents in the presence of an appropriate protonating agent (HCl) by lowering the solubility of the PGM chlorido-anions through an ion-pairing mechanism. The recovery of RhIII from synthetically prepared PGM (RhIII and PtIV) containing solutions using these precipitants was excellent, while poor Rh recovery from authentic industrial process solutions was achieved. The poor Rh recovery from these process solutions was ascribed to the species distribution of the [RhCln(H2O)6-n]3-n complexes. In order to validate the proposition that RhIII speciation effects are responsible for the poor Rh recovery observed during the precipitation studies, attempt were made to describe the species distribution of the [RhCln(H2O)6-n]3-n (n=3-6) by means of high-resolution 103Rh NMR spectroscopy. A detailed high-resolution 103Rh NMR spectroscopic study of the series of [RhCln(H2O)6-n]3-n (n=3-6) complexes was conducted. During this study, all six RhIII aqua chlorido-complexes have unambiguously been characterized by means of high-resolution 103Rh NMR spectroscopy, proving the powerful analytical capability of this technique. Characterization of these complexes is based on the detailed analysis of the 35Cl/37Cl isotope effects which is observed in the 19.11 MHz 103Rh NMR resonances of the [RhCln(H2O)6-n]3-n (n=3-6) complexes in aqueous HCl solutions at 292 K. These resonances show that the “finestructure” of each of the 103Rh resonances may be understood in terms of its unique isotopologue, and in certain cases, the isotopomer distribution of each complex, which manifests as a result of its statistically expected 35Cl/37Cl isotopologue and isotopomer distributions. As a result, the 103Rh NMR resonance structure serves as a unique “NMRfingerprint”, which allows for the unambiguous assignment of [RhCln(H2O)6-n]3-n (n=3-6) complexes, without the reliance on accurate δ(103Rh) chemical shifts. Furthermore, this study reports the first direct species distribution diagram for the [RhCln(H2O)6-n]3-n (n=3-6) series of complexes (in aqueous HCl solutions at 292 K) as a function of the “free” (unbound) chloride concentration, constructed from 103Rh NMR measurements. The need for a revised speciation diagram of [RhCln(H2O)6-n]3-n (n=3-6) complexes is clearly reflected by the vast differences observed in the literature reported species distribution diagrams, which makes it difficult to decide which set of experimental conditions (if any) is required for the quantitative and “selective” recovery of RhIII from aqueous HCl solutions containing associated PGMs (Pt, Pd, Ir, Ru) as well as other transition metals. The documented species distribution diagrams for RhIII have been generally constructed via data from indirect (kinetic and spectrophotometric) measurements using dilute RhIII solutions at relatively high HCl concentrations, which implies that the RhIII:Clmole ratio is higher than what may be expected in authentic process solutions – an important aspect to consider when optimizing RhIII recovery methods. In addition, RhIII kinetic investigations reported in this study shows that ionic strength and temperature effects are important factors that dramatically influences the rate of RhIII ligand exchange (i.e. RhIII aquation reactions) which, in turn, have contributing effects on the species distribution of [RhCln(H2O)6-n]3-n complexes. Notable differences exist between the speciation diagram reported in this study and those documented in literature, especially at a “free” chloride concentration of 1.0 M. At this “free” chloride concentration, the [RhCl5(H2O)]2- complex anion was found to have an abundance of 34%, while literature reports an abundance of 80%. In order to ascertain its practical relevance, the proposed 103Rh NMR speciation method was extended, for the first time, to authentic industrial Rh feed solutions (Anglo Platinum PLC). Each of the 103Rh resonances was unambiguously assigned, and each species quantified. Moreover, the RhIII species distribution of the industrial Rh feed solution was accurately predicted by the “direct” speciation diagram constructed form 103Rh NMR measurements. After careful optimization of the Heraeus industrial feed solutions (optimal chloride concentration followed by thermal treatment for enhancing RhIII chloride anation reactions), the recovery of Rh via precipitation was repeated. In this instance, Rh recovery improved dramatically, with up to 95% of Rh removed from solution. This improvement is ascribed primarily to the increased “free” (unbound) chloride concentration. The presence of associated PGMs as well as other transition metals would lower the effective “free” chloride concentration, since these metals would act as “chloride binders”. By adjusting the total chloride concentration, RhIII chloride anation reactions is enhanced which leads to the [RhCln(H2O)6-n]3-n (n=5,6) complex anions being the dominant species in solution, therefore leading to improved Rh recovery. Moreover, it was shown that, under carefully controlled conditions, “selective” recovery of Rh is achieved using tris(2-aminoethyl)amine (Tren). Considering the fact that Rh is the last precious metal recovered in all PGM refineries, this can possibly provide a cost-effective route for the “upfront” (early stage) recovery of Rh from industrial PGM feed solutions. / AFRIKAANSE OPSOMMING: In hierdie tesis word die herwinning van RhIII uit laboratorium voorbereide sowel as ware industriële PGM-bevattende oplossings sistematies ondersoek deur middel van organiese neerslag metodes, deur gebruik te maak van verskeie kommersieël beskikbare, Nbevattende organiese reseptore insluitende dietileentriamien (Deta), tri-etileentetramien (Teta), tetra-etileenpentamien (Tepa) en tris(2-aminoetiel)amien (Tren). Hierdie organiese reseptore tree op as neerslag-agente in die teenwoordigheid van 'n geskikte protoneringsagent (in hierdie geval HCl) deur 'n verlaging van die oplosbaarheid van die PGM chloriedanione deur middel van 'n ioon parings meganisme. Die herwinning van RhIII vanuit laboratorium voorbereide PGM (RhIII en PtIV) oplossing met behulp van hierdie organiese neerslag-agente was uitstekend, terwyl Rh herwinning vanuit ware industriële oplossings swak was. Die onvolledige Rh herwinning uit hierdie industriële oplossings word toegeskryf aan die spesie-verspreiding van die [RhCln(H2O)6-n]3-n komplekse. Ten einde die effek van RhIII spesie-verspreiding op die herwinning van Rh te bestudeer, is gepoog om die spesieverspreiding van [RhCln(H2O)6-n]3-n (n=3-6) komplekse, deur middel van hoë resolusie 103Rh KMR spektroskopie, te beskryf. 'n Gedetailleerde hoë resolusie 103Rh KMR spektroskopiese studie van die reeks van [RhCln(H2O)6-n]3-n (n=3-6) komplekse was uitgevoer. Tydens hierdie studie was al ses RhIII aqua chlorido-komplekse ondubbelsinnig gekarakteriseer deur middel van hoë resolusie 103Rh KMR spektroskopie, wat bewys lewer van die kragtige analitiese vermoë van hierdie tegniek. Karakterisering van hierdie komplekse is gebaseer op die gedetailleerde analise van die 35Cl/37Cl isotoop effekte wat waargeneem word in die 19.11 MHz 103Rh KMR resonansies van die [RhCln(H2O)6-n]3-n (n=3-6) komplekse in HCl oplossings by 292 K. Hierdie resonansies toon dat die "fyn struktuur" van elk van die 103Rh resonansies verstaan kan word in terme van die unieke isotopoloog, en in sekere gevalle, die isotopomeer verspreiding van elke kompleks, wat manifesteer as 'n gevolg van die die statisties verwagte 35Cl/37Cl isotopoloog en isotopomeer verspreiding. Die 103Rh KMR resonansie-struktuur kan sodoende dien as 'n unieke "KMR-vingerafdruk", wat voorsiening maak vir die ondubbelsinnige karakterisering van [RhCln(H2O)6-n]3-n (n=3-6) komplekse, sonder om vertroue op akkurate δ(103Rh) chemiese verskuiwings te plaas. Hierdie studie rapporteer verder die eerste direkte spesie-verspreiding-diagram vir die [RhCln(H2O)6-n]3-n (n=3-6) reeks komplekse (in HCl oplossings by 292 K) as 'n funksie van die "vrye"(ongebonde) chloried-konsentrasie, verkry van 103Rh KMR metings. Die behoefte vir 'n aangepasde spesiasie-diagram vir die [RhCln(H2O)6-n]3-n (n=3-6) komplekse word duidelik weerspieël deur die groot verskille waargeneem in die literatuur gerapporteerde verspreidings diagramme, wat dit moeilik maak om te besluit watter stel eksperimentele toestande (indien enige) benodig word vir die kwantitatiewe en “selektiewe” herwinning van RhIII in HCl oplossings in die teenwoordigheid van gepaardgaande PGM (Pt, Pd, Ir, Ru) sowel as ander oorgangsmetale. Die gedokumenteerde spesie-verspreiding-diagramme vir RhIII is oor die algemeen verkry via data vanaf indirekte (kinetiese en spektrofotometriese metings) deur gebruik te maak van verdunde RhIII oplossings in relatiewe hoë HCl konsentrasies, wat impliseer dat die RhIII:Cl mol verhouding hoër is as wat verwag kan word in ware industriële proses oplossings - 'n belangrike aspek om te oorweeg gedurende die optimalisering van RhIII herwinning-metodes. Verder, die RhIII kinetiese ondersoeke gerapporteer in hierdie studie toon dat ioniese sterkte sowel as temperatuur effekte belangrike faktore is wat die tempo van RhIII ligand uitruiling (d.w.s. RhIII “aquation” reaksies), wat ‘n betekenisvolle invloed hê op die spesie-verspreiding van [RhCln(H2O)6-n]3-n komplekse. Aansienlike verskille bestaan tussen die spesiasie-diagram gerapporteer in hierdie studie en dit gedokumenteer in die literatuur, veral by 'n "vrye" chloried-konsentrasie van 1.0 M. By hierdie "vrye" chloried-konsentrasie was die [RhCl5(H2O)]2- komplekse anioon gevind om in 34% teenwoordig te wees (hierdie studie), terwyl die publiseerde verslae 80% rapporteer. Ten einde die praktiese toepaslikheid van die voorgestelde 103Rh KMR spesiasiemetode te bepaal, was (vir die eerste keer) ware industriële Rh oplossings (Anglo Platinum PLC) gebruik. Elk van die 103Rh resonansies was ondubbelsinnig gekarakteriseer, en elke Rh spesie teenwoordig gekwantifiseer. Daarbenewens is die RhIII spesie-verspreiding van die industriële Rh oplossing deur die "direkte" spesiasie-diagram saamgestel vanuit 103Rh KMR metings akkuraat voorspel. Die berekende RhIII spesie-verspreiding van die industriële Rh oplossings was akkuraat voorspel deur die voorgestelde “direkte” spesiasie-diagram soos saamgestel vanuit die 103Rh KMR metings. Na deeglike optimalisering van Heraeus industriële oplossings (optimale chloriedkonsentrasie gevolg deur termiese behandeling vir effektiewe RhIII chloried anasie reaksies), is die herwinning van Rh via neerslag metodes herhaal. In hierdie geval, het die Rh herwinning dramaties verbeter, met tot 95% van die Rh uit oplossing verwyder. Hierdie verbetering is hoofsaaklik toegeskryf aan die verhoogde "vry" (ongebonde) chloriedkonsentrasie. Die teenwoordigheid van geassosieerde PGM's sowel as ander oorgangsmetale sal die effektiewe "vrye" chloried-konsentrasie verlaag, aangesien hierdie metale sou optree as "chloried-binders". Deur die aanpassing van die totale chloried-konsentrasie, word RhIII chloried anasie reaksies verbeter, wat daartoe lei dat [RhCln(H2O)6-n]3-n (n = 5,6) komplekse anione die dominante spesies in oplossing word, en dus lei tot verbeterde Rh herwinning. Daarbenewens word verder aangetoon dat, onder noukeurig gekontroleerde voorwaardes, "selektiewe" herwinning van Rh bereik word deur gebruik te maak van tris(2-aminoetiel)amien (Tren). Met inagneming van die feit dat Rh die laaste edelmetaal is wat verhaal word in alle PGM-raffinaderye, kan dit 'n koste-effektiewe roete word vir die "vooraf" (vroeë-stadium) herwinning van Rh vanuit industriële PGM bevattende oplossings.

Thesis (PhD)--Stellenbosch University, 2013. / Please refer to full text to view abstract.

The use of solid-state NMR and DFT calculations to study Y₂Sn[subscript(x)]Ti[subscript(2-x)]O₇, Y₂Sn[subscript(x)]Zr[subscript(2-x)]O₇ and Y₂Ti[subscript(x)]Zr[subscript(2-x)]O₇, materials with applications for the safe encapsulation of radioactive actinides is investigated. As a result of cation or anion disorder in these materials, NMR spectra are often complex and difficult to interpret. Therefore, an investigation using a range of NMR active nuclei and measurement of a variety of NMR parameters (isotropic chemical shift, δ[subscript(iso)]; span, Ω and quadrupolar coupling, C[subscript(Q)]) were used to provide a full and detailed picture of each material. The measurement of Ω in these disordered compounds with multiple resonances in the NMR spectra, required the use of 2D CSA-amplified PASS (CAPASS) experiments to enable the separation of each of the spinning sideband manifolds. An experimental assessment of the CAPASS experiment showed that although low ν₁/Ω[subscript(Hz)] ratios (as found in ⁸⁹Y NMR) resulted in distortions in the spectra obtained, a modified fitting procedure could be utilised to compensate for this fact, which allowed the accurate measurement of Ω. Despite the difficulties in acquiring the ⁸⁹Y NMR spectra, they were found to be the most informative of the NMR-active nuclei available. ¹¹⁹Sn NMR spectra, although much easier to acquire than ⁸⁹Y, were more complex and harder to analyse, owing to the overlapping resonances. Therefore, ¹¹⁹Sn NMR could only be used to confirm or support the results obtained using ⁸⁹Y NMR. Although ¹⁷O NMR was found to be useful, a full study could not be implemented due to the lack of ¹⁷O enriched samples; an area where future investigation may prove fruitful. Finally, [superscript(47/49)]Ti and ⁹¹Zr NMR spectra were found to be the most difficult to acquire due to their low receptivities and the quadrupolar broadened lineshapes, and as a result, little additional information was obtained. As a result of this analysis, for the Y₂Sn[subscript(x)]Ti[subscript(2-x)]O₇ pyrochlore solid solution, using primarily ⁸⁹Y δ[subscript(iso)] and Ω, and additionally confirmed with ¹¹⁹Sn δ[subscript(iso)], it was found that the Sn and Ti cations were randomly ordered throughout the B-sites. Additionally, ⁸⁹Y Ω could be used to obtain approximate Y-O[subscript(48f)] and Y-O[subscript(8b)] bond lengths for each type of Y environment. The study of Y₂Sn[subscript(x)]Zr[subscript(2-x)]O₇ using ⁸⁹Y NMR showed that although the end members were single phase, pyrochlore (Y₂Sn₂O₇) or defect fluorite (Y₂Zr₂O₇), the intermediate compositions were mostly two phase mixtures, consisting of an ordered pyrochlore (with an average formula of Y₂Sn₁.₈Zr₀.₂O₇) and a disordered phase, where the proportions of the pyrochlore and disordered phases decreased and increased, respectively, with the Zr content. Additionally, although the coordination states of the Y and Sn cations were easily determined using ⁸⁹Y and ¹¹⁹Sn NMR, respectively, the coordination states of the Zr cations could not be confirmed directly by ⁹¹Zr NMR. However, using indirect analysis from results obtained with ⁸⁹Y and ¹¹⁹Sn NMR, it was determined that 6 coordinate Zr was present in each composition, and it was always present in a greater proportion than 8 coordinate Zr. Finally, although ⁸⁹Y NMR spectra of Y₂Ti[subscript(x)]Zr[subscript(2-x)]O₇ were extremely difficult to analyse, it was tentatively proposed that they could be similar to Y₂Sn[subscript(x)]Zr[subscript(2-x)]O₇ due to some similarities observed between the spectra.