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Soon after the importance of Nuclear Magnetic Resonance Spectroscopy was established more sophisticated instruments started coming into use. At present High Resolution Spectroscopes which are of the self-recording type are extensively used in research. However, the high cost of the instrument prevents its use in smaller and poorer schools. In recent years a low cost instrument of the single coil type has been constructed by the Aero Medical Laboratory which is alright for demonstration purposes but cannot be used for research because of low resolution. The idea of the present project was to see whether a similar instrument of double coil type could be made at a low cost of about $200. This instrument could give the proton resonance peak of water and be used for demonstration purposes.

The increased demand for electric vehicles in recent years has driven the development of Li ion battery technology, yielding interesting trends in cathode materials. The layered cathode material Li(Ni1/3Mn1/3Co1/3)O2 gives 30% more reversible lithium extraction than the earlier LiCoO2 and the “overlithiated” material Li(Li0.2Mn0.54Ni0.13Co0.13)O2 gives a semi-reversible capacity 25% higher than Li(Ni1/3Mn1/3Co1/3)O2.1,2 6,7Li MAS NMR and 7Li MATPASS NMR were used to investigate the relation between the lithium ion and metal positions within these materials. It was found that Li(Ni1/3Mn1/3Co1/3)O2 showed a preference for Li ions to associate with Co at high voltages, that Mn4+ and Ni2+ showed some association and that the metals were not highly ordered. Li(Li0.2Mn0.5Ni0.13Co0.13)O2 showed a decrease in transition metal layer lithium upon cycling, in agreement with previous models, an ordering of the metal ions with the reinsertion of the lithium ions and a significant change in structure on deep discharge.3 These results will hopefully lead to more accurate modelling of the materials, understanding of reversibility and to increased reversible capacities in future cathode materials. Additionally work was done to enable high rate in-situ NMR spectra in which spectra are obtained from a cell while cycling in the bore of an NMR spectrometer. A Teflon Swagelok-style cell was designed and the effectiveness of solenoid and saddle coils were tested. It was found that for a 6 mm diameter cathode with a Li metal anode, at least half of the signal intensity could be obtained with a saddle coil whereas the signal was not detected when using a solenoid coil. / Thesis / Master of Science (MSc)

<p> Studies of the bonding and reactivity of transition metal complexes constitute a large fraction of current research in inorganic chemistry. The present thesis describes three contributions to this area. In each case, Nuclear Magnetic Resonance studies of paramagnetic complexes are involved. An introductory chapter briefly reviews some of the pertinent background. In the second chapter the NMR theory which forms the basis for interpreting the experimental results is developed. </p> <p> The major topic of the thesis is concerned with the effect of ligand substitution on the charge distribution of a transition metal complex. Interest in this topic is aroused by the many reports that the reactivity of transition metal complexes can be considerably affected by modification of the ligands. This is particularly notable in the area of homogeneous catalysis. It seemed possible that NMR studies of paramagnetic complexes might provide a probe for these effects. With this objective in view the NMR spectra of a series of trisβ diketonato V(III) complexes have been examined. It was found that substituent changes on one ligand brought about very large (several thousand Hz) changes in the isotropic shifts of protons or fluorine atoms located on another ligand. A rather complete study has been carried out on the series of complexes formed by systematically substituting CF₃ groups for CH₃ groups on tris-acetyl-acetonato V(III). Ninety-nine of the possible one hundred different ¹H and ¹⁹F resonances in this system have been observed and identified. This relatively large body of data enabled us to attempt an empirical analysis of the results in terms of changes in the charge distribution in the complex brought about by substitution. Arguments are presented to show that the isotropic shifts arise predominantly from contact interactions. It was found necessary to introduce two terms in the empirical equations describing the shifts. The first represents changes in the distribution of the unpaired electrons in the Vanadium(III) d orbitals brought about by modification of the crystal field potential produced by the ligands. The second represents variations in the ability of a ligand to accept electron density by metal to ligand charge transfer due to inductive effect of the substituent. Two term empirical equations of this type reproduce the observed shifts to within 2%. The significance of the parameters obtained from this analysis is discussed in some detail. These studies have been extended to include several other substituted β-diketone ligands. A similar analysis has proved feasible and a consistent pattern of substituent parameters is obtained. </p> <p> The second topic considered is closely related to the above study. The interest in this case was in the possible importance of dipolar shifts in determining the isotropic shifts of mixed chelates. A series of six coordinated Co(II) complexes wa.a chosen for this purpose. These compounds are known to possess considerable magnetic anisotropy and dipolar shifts are therefore to be expected. However analysis of the results reveals that the substituent shifts are very similar to those for the V(III) compounds. It appears that the mode of transmission of substituent effects proposed may be quite general for many transition metal complexes. </p> <p> The third topic involved in this thesis concerns the structure of the second coordination sphere of transition metal complexes. The participation of various solvents in the second coordination sphere of tris-pyrazolylborate Co(II) has been investigated. Equilibrium constants relative to carbon tetrachloride as a second sphere ligand have been obtained. The ability of a solvent to participate in the second sphere depends predominantly on its dipole moment and it is concluded that Van der Waals forces are responsible for outer sphere binding. </p> / Thesis / Doctor of Philosophy (PhD)

The quadrupole coupling tensors at the B11 and Na23 sites in borax and tincalconite, two members of the hydrated sodium tetraborate family have been completely evaluated using broadline nuclear magnetic resonance (n.m.r.) techniques. The results have enabled deductions to be made concerning the crystal chemistry of boron, the coordinations of the sodium atoms and the crystallographic symmetries. Changes in the Li7 n.m.r. spectrum of ferroelectric lithium hydrazinium sulphate as a function of temperature were followed in detail. A previously undetected second order phase transition leading to a high temperature polymorph is complete at 164°C, The quadrupole coupling tensors at the Li7 sites have been completely evaluated in the two phases. The second moments or the proton n.m.r. spectrum from powdered lithium hydrazinium sulphate have been determined within the temperature range -183°C to 225°C, and single crystal data on the protons have been obtained at room temperature. It is shown that the nitrogen and hydrogen atoms exist in the structure as the hydrazinium ion NH2 and-NH3+. Detailed information is derived concerning the proton-proton vectors and the modes of reorientation of the NH2 and-NH3+ groups at various temperatures. Mechanisms for the ferro-electric switching at room temperature and for the transition to the high temperature polymorph are proposed on the basis of the experimental evidence. / Thesis / Doctor of Philosophy (PhD)

<p> The temperature dependences of the deuteron spin-lattice relaxation times, T1, in ferroelectric ammonium sulfate, (ND4)2SO4 , and ammonium fluoroberyllate, (ND4)2BeF4, have been studied by transient methods over the range 80 to 47S°K. The ability to resolve the individual correlations of the two independent ND4 groups in the deuteron experiment has thrown new light on the reorientation of the ammonium groups and their behaviour in the phase transition. It has been proposed that the mechanism of the phase transition in ammonium sulfate is a disordering, with respect to the a b plane in the paraelectric phase, of the ND4 dipoles which also make the dominant contribution to the spontaneous polarization. The present N.M.R. results show that in (ND4)2so4 ,T1 at both non-equivalent ND4 groups is affected at the phase transition, whereas in (ND4)2BeF4 , it is affected at only one ND4 group. This suggests that the phase transitions in these two materials are rather different and that in ammonium sulfate both types of ammonium ions are involved whereas in ammonium fluoroberyllate only one type is involved in the transition. Such a conclusion is supported by evidence from measurements of thermal and dielectric properties. An earlier study of the proton spectrum in (NH4)2so4 reported a value of 33 gauss^2 for the second moment at 20°K. This is considerably smaller than the expected rigid lattice value of 5O gauss^2 and it was concluded that while some of the NH4+ groups are effectively rigid at 20°K others are still reorienting. Our new results for the proton second moment confirm the low value down to 4.2°K but our results for T1 indicate that the proton line is not motionally narrowed. </p> / Thesis / Doctor of Philosophy (PhD)

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The nuclear magnetic resonance spectrum and the spin lattice relaxation time of protons in powdered hydrated gallium sulfate have been investigated and compared in order to determine the probable proton configurations. The second moment and the relaxation time of the proton resonance were studied over a wide range of temperature. The NMR evidence is compatible with the existence of protons in OH-and H30+ configurations supporting the suggestion of Johansson (1962) based on an x-ray structure analysis. / Thesis / Master of Science (MS)

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