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NMR spectroscopy is a very powerful technique for the characterization of structure and dynamics of a variety of systems starting from small organic molecules to large biological macromolecules. In solids, the study of protons becomes more interesting because they are very sensitive to inter-molecular packing and are directly involved in hydrogen-bonding and aromatic π-π interactions, etc. The present thesis is devoted essentially to utilizing information from proton resonances obtained using multinuclear and multiple-quantum approaches. The thesis has two parts. The first part deals with methodological developments in the area of solid-state NMR, relevant to the study of rigid powder samples as well as partially ordered liquid crystalline materials. Methods have been proposed to investigate the structure of small molecules at moderate spinning frequencies and thermotropic liquid crystals at static conditions. Proton detected heteronuclear experimental methods based on both first and second-order cross polarization at moderate and ultra-fast magic angle spinning rates are also proposed. The second part of the thesis deals with the application of both newly proposed and existing solid state NMR methods to the study of several biologically relevant systems. These include the study of several designed as well as naturally occurring peptides. The use of first-principles calculations based on GIPAW method for supporting the experimentally obtained results has also been made. The thesis is divided into five chapters. In the second chapter, a new pulse sequence to correlate Double Quantum (DQ) proton frequencies to carbon Single Quantum (SQ) chemical shifts in the solid state has been proposed. In this sequence, named as MAS-J-1H (DQ)-13C-HMQC, the correlation between 1H and 13C is achieved through scalar coupling, while the double-quantum coherence among protons is generated through dipolar couplings. This experiment is particularly suited for the study of 13C in natural abundance. The advantages of the technique with applications to alanine, histidine and a model liquid crystalline material have been demonstrated. The assignment of 13C spectra of partially ordered systems has also been considered. In this case the assignment of the spectrum is a major challenge due to the interplay of anisotropic order and chemical shift parameters. The DQ-SQ correlation experiment described in the thesis has been applied to a well known liquid crystal and also to a novel thiophene based liquid crystal and the local order parameters of the liquid-crystal have been obtained. The thesis also presents results on the azelaic acid -isonicotinamide co-crystal as well as the drug ibuprofen obtained by using novel methodologies. In the case of the former, the problem of overlap of resonances was overcome with the use of the REVERSE-CP approach to separate out the carbon attached protons from the rest of the protons. Subsequently, by the use of several combined approaches, the structural features were identified. A new heteronuclear correlation pulse sequence for solids under fast MAS conditions has also been tested. With low r.f powers, a second-order dipolar term mediated transfer of magnetization between I and S spin known as second order cross-polarization (SOCP) was exploited to obtain the entire spin system connectivity. Both carbon detected and proton detected experiments have been carried out and their utility evaluated. Similar approaches to shed light on the structure and conformation of a set of proline and pseudoproline based designed β-turn peptides that are used as templates for understanding protein folding have been made. Results of studies on two biologically important forms of the short-chain peptides namely glutathione reduced (GSH) and oxidized (GSSG) tripeptides are also presented.

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Since the development of the ruthenium containing precatalysts Grubbs 1 (1) and Grubbs 2 (2), there was an increase in the development of new precatalysts. The NMR characterization could not cope with this. The NMR characterization mainly consists of 1H, 31P, COSY and rarely 13C. Due to the high natural abundance of 1H and 31P (99.98% and 100%), these experiments could be carried out quickly and easily. The only change that had to be made was to the spectral width, to accommodate the carbene signal (Ru=CH) between δ 20.02 and δ 17.32 ppm. The lack of 13C characterization is attributed to the low natural abundance of these nuclei that is only 1.10% and the lack of published parameters. Furthermore, the broad spectral width of 300 ppm increases the difficulty because the number of scans has to be increased to increase the sensitivity of the spectra and obtain useful data. In this study the precatalyst 1 was used to learn the NMR technique as well as to acquire the NMR parameters. 2 and two other commercial Grubbs-type precatalysts 3 and 4 underwent NMR characterization so that acquired values could be compared with the literature. Six other non-commercial Grubbs-type precatalysts 5-10 were synthesized and characterized. Due to the instability of the precatalysts and taking into account the duration of these experiments, the characterization was done over three steps. The first step was to do the following experiments: 1H, COSY, HSQC and HMBC, which took four hours. The next step was the DEPT135 experiment of three hours, and finally the 13C experiment of seven hours. The maximum amount of information could be obtained in this way. The combined NMR parameters for this study was obtained and used to characterize the Grubbs-type precatalysts 5-10 partially. Due to the large amount of overlapping peaks in the aromatic and alkane areas the resolution was not sufficient for full characterization. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

Since the development of the ruthenium containing precatalysts Grubbs 1 (1) and Grubbs 2 (2), there was an increase in the development of new precatalysts. The NMR characterization could not cope with this. The NMR characterization mainly consists of 1H, 31P, COSY and rarely 13C. Due to the high natural abundance of 1H and 31P (99.98% and 100%), these experiments could be carried out quickly and easily. The only change that had to be made was to the spectral width, to accommodate the carbene signal (Ru=CH) between δ 20.02 and δ 17.32 ppm. The lack of 13C characterization is attributed to the low natural abundance of these nuclei that is only 1.10% and the lack of published parameters. Furthermore, the broad spectral width of 300 ppm increases the difficulty because the number of scans has to be increased to increase the sensitivity of the spectra and obtain useful data. In this study the precatalyst 1 was used to learn the NMR technique as well as to acquire the NMR parameters. 2 and two other commercial Grubbs-type precatalysts 3 and 4 underwent NMR characterization so that acquired values could be compared with the literature. Six other non-commercial Grubbs-type precatalysts 5-10 were synthesized and characterized. Due to the instability of the precatalysts and taking into account the duration of these experiments, the characterization was done over three steps. The first step was to do the following experiments: 1H, COSY, HSQC and HMBC, which took four hours. The next step was the DEPT135 experiment of three hours, and finally the 13C experiment of seven hours. The maximum amount of information could be obtained in this way. The combined NMR parameters for this study was obtained and used to characterize the Grubbs-type precatalysts 5-10 partially. Due to the large amount of overlapping peaks in the aromatic and alkane areas the resolution was not sufficient for full characterization. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014

There is a continuing interest in the subject of arene carbonylation, especially in strong acids and environmentally-benign alternatives are sought to HF/BF3 and to AlCl3 as conversion agents. Ionic liquids offer a powerful solvent for useful conversion agents such as aluminum chloride. The ILs permit AlCl3 to be used at lower HCl partial pressures than with other solvents. The superior reactivity demonstrated by acidic, chloroaluminate ILs is probably due to their enhanced solvation power for HCl and CO. Addition of HCl gas increased reactivity of the system by forming Brnsted acids, and toluene carbonylation is a Brnsted demanding reaction. It was found that reaction is stoichiometric in Al species and only intrinsically acidic ILs are active for toluene carbonylation, therefore it was possible to correlate observed conversion with predicted amounts of Lewis + Brnsted acids. Molecular modeling provided information about the different species present in these ILs and predicted 1H NMR, and 27Al NMR spectrum. Predictions suggested that three types of HCl species are present; and these predictions were confirmed using data of 13C-labeled acetone and its 13C-NMR spectra. These data showed that only one of the three types of HCl in the IL were super acidic. Reactivity towards arene formylation can be tuned by adjusting the ligands R and R in the organic cation and by changing the anion. This reactivity tuning can be exploited in a process where high acidity is required for the conversion of substrate but where separation of product from IL is facilitated by low acidity.

Das Ziel der Arbeit war es, Skalenverhalten und Lösungseigenschaften von flexiblen Dendrimeren als Modell für hochverzweigte Polymere zu untersuchen. Als Untersuchungsmethode wurde die gepulste Feldgradienten NMR (PFG-NMR) eingesetzt, um das hydrodynamische Verhalten der Dendrimere in Lösung zu erforschen. Aus der Konzentrationsabhängigkeit des Diffusionskoeffizienten konnte abgeleitet werden, dass das Verhalten der PAMAM-Dendrimere dem von Proteinen ähnelt, die Dendrimere also starr und globulär sind. Um die Abhängigkeit des hydrodynamischen Radius von der Molmasse zu untersuchen, kamen Lösungen von mehreren Generationen PAMAM-Dendrimeren mit verschiedenen Endgruppen zum Einsatz. Mit PFG-NMR wurden die Diffusionskoeffizienten bestimmt, aus denen die hydrodynamischen Radien nach der Stokes-Einstein-Beziehung berechnet wurden. Ein Skalenansatz lieferte die beste Beschreibung der Daten für alle drei untersuchten Systeme. Die ermittelten Skalenexponenten waren u = 3,7 für alle untersuchten PAMAM-Dendrimere. Dies bedeutet, dass deren Wachstum im dreidimensionalen Raum begrenzt ist, da der Skalenexponent einen Wert größer drei annimmt. Die Art der Endgruppen hatte in diesem Fall keinen erkennbaren Einfluss auf das Skalenverhalten. An Lysin-Dendrimeren wurde der Einfluss der Kernfunktionalität auf den Skalenexponenten untersucht. Die Lysin-Dendrimere standen als Monodendren (Kernfunktionalität, KF=1) und als Dendrimere mit einem Thiacalixaren-Kern (Thia1: KF=2, Thia2: KF=4) zur Verfügung. Die Skalenexponenten waren folgende: Für das Monodendron war u = 2,0, für Thia1 war u = 2,3 und Thia2 hatte einen Skalenexponent von u = 3,9. Da die Dendren in allen drei Fällen identisch waren, muss dieser Unterschied durch den Kern begründet sein. Weiter wurde die effektive Ladung von PAMAM-COONa G1,5 Dendrimeren in verdünnter D2O-Lösung als Funktion des pH-Werts mit Hilfe von Elektrophorese-NMR untersucht. Dabei änderte diese sich von Zeff = -5 e bei pH 12,6 zu Zeff = +5 e bei pH 1,8.