Nuclear magnetic resonance studies in single crystals of thallium have been performed for the first time. The resonance frequency, line width and second moment were studied as a function of crystal orientation with respect to the magnetic field. The Knight shift parameters were determined at liquid helium and liquid nitrogen temperatures. The anisotropic Knight shift results were in disagreement with the results obtained on powder specimens by other workers. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Satellite lines originating from the first nearest neighbours have been observed on the Al²⁷ N.M.R. spectrum in dilute single crystal samples of Al-Mn and Al-Cr. The field and orientation dependence of the satellite position has revealed the quadrupole coupling constant and asymmetry parameter of [formula omitted] = 60 ± 1kHz and [formula omitted] = -0.01 ± 0.005 for Al-Cr, and [formula omitted] = 19 ± 1kHz, [formula omitted] = -0.08 ± 0.02 for Al-Mn. An anisotropic magnetic perturbation of ∆ K[₁₁₁] = -0.05 ± 0.01% and ∆ K[₀₀₁] = -(0.07 ± 0.1)% in Al-Mn is attributed to a spin density perturbation at the impurity sites. The Al-Cr results agree with those of Janossy and Gruner [18] and Minier and Berthier [22]. The satellite line observed in the Al-Mn system was also seen by Launois and Alloul [2], with approximately the same values of [formula omitted] and ∆ K. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A series of isomeric, six-membered, cyclic phenyl phosphate esters has been obtained by column chromatography of the mixtures of isomers obtained by reaction of phenyl phosphorodichloridate with appropriate 1,3-diols. The conformational analysis of the isomers was undertaken using both ¹ʜ and ³¹p n.m.r.. The basic conformation of the 2 oxo-2-phenoxy-1,3,2-dioxaphosphorinane ring system is that of a "flattened-chair". The thermodynamic free energy difference between "chair" conformations is sufficiently large for the basic ring to exist essentially in one favoured conformation, rationalized to have an axial phenoxy substituent. The stereospecific nature of Jpoch has been confirmed by using ¹ʜ n.m.r. to determine conformations. Long-range, ⁴J, ³¹p- ¹ʜ coupling constants have been found to be stereospecific in nature and useful in facilitating assignment of conformations for methyl-substituted-2-oxo-2-phenoxy-l,3,2-dioxaphosphorinanes. Similar ring systems having different substituents at phosphorus have been studied and the conformations of these derivatives are seen to differ depending on the nature of the phosphorus substituent. The conformation of a cyclic nucleotide has been determined from its ³¹p n.m.r. spectrum. The use of computer programming techniques and hetero-nuclear double resonance techniques, greatly facilitated the analysis of the n.m.r. spectra discussed. An interesting deceptively-simple type of ABX n.m.r. spectrum has been found for many of these cyclic phosphate derivatives and the explicit analysis of this system is presented. / Science, Faculty of / Chemistry, Department of / Graduate

The nuclear magnetic resonance in single crystal magnesium has been studied at 4.2°K. The isotropic Knight shift, the anisotropic Knight shift and the quadrupole interaction have been investigated. The values for the parameters measured are K = (0.1127 ± 0.0005)%, K' = (0.0004 ± 0.0002)%, e²qQ/h = 324 ± 6 KHz. These results are compared with those of Rowland in powdered magnesium to reveal the Knight shift is independent of temperature. This contrasts directly with the behavior of cadmium. The quadrupole interaction is shown to increase by 40% as temperature is lowered to 4.2°K from room temperature. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Proton and fluorine nuclear magnetic resonance spectroscopy was used to investigate the favoured forms of several furanosyl fluorides. The low energy barrier to pseudo-rotation in these systems precludes the assignment of only one favoured conformation for each molecule. A systematic study of five membered ring sugar conformations was undertaken by examining three types of systems, varying from a relatively rigid molecule involving three fused rings, to more flexible molecules involving a "free" furanosyl fluoride ring. The spectral assignment was greatly facilitated by heteronuclear fluorine decoupling and computer analysis. 5-fluoro-3,6-anhydro-α-L-idofuranose was synthesized in good yield from several precursors and the molecule's furanose ring conformation of ₂T³was assigned on the basis of vicinal ¹H-¹H coupling constants. Using the values for vicinal ¹H- ¹⁹F couplings obtained from this molecule, together with data from other workers, a partial Karplus type curve was constructed relating vicinal ¹H- ¹⁹F couplings to dihedral angles. This curve - which was found to be more asymmetric than the Karplus relationship for vicinal ¹H-¹H couplings - was then used, together with the known Karplus curve for vicinal ¹H-¹H couplings, to determine the conformations of the triester furanosyl fluorides of ribose, arabinose and xylose. Assuming pure sp³ hybridization and maximum ring puckering, the conformations for most of the sugars studied were found to involve the displacement of C₂ and/or C₃ positions out of the plane of the ring formed by the other atoms. The conformation for α-fluoro-ribo-furanosyl triester ( ₃T⁴ ) was found to be different than that of the β-fluoro-ribofuranosyl triester (₃T⁴). A significant and apparently stereospecific long-range ⁴J[subscript H].₄,F coupling through oxygen of ca. 6.5 Hz, is observed when H₄ and F are in a trans arrangement, while a much smaller coupling for ⁴J[subscript H].₄,F of ca. 1.0 Hz. is observed when these two nuclei are in a cis or approximately "planar M" arrangement. On the other hand, ⁴J[subscript H].₃,F couplings were found to have a value of ca. 2.2 Hz. in the cis or "planar M" geometry, while in the trans geometry, ⁴J[subscript H].₄,F is ca. 0.5 Hz. / Science, Faculty of / Chemistry, Department of / Graduate

Resonance absorption spectra have been observed which may be interpreted as many-quantum transitions where the axis of quantization is along the effective magnetic field in the rotating frame. By this description, resonances which required up to five quanta were observed. The spin system used was that of conduction electrons of lithium metal in neutron irradiated lithium fluoride crystals. An analysis of the experimental results using a modified Bloch equation under the assumption that Ƭ₁= Ƭ₂= Ƭ 1.5x10 ̄⁷sec. and that the spin system relaxes toward the instantaneous field is presented. A brief outline of the concept of spin temperature is included. A comparison is made between some of the predictions of the spin temperature concept and the simple Bloch theory used in analyzing the experimental data. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Spin-lattice relaxation times have been measured in metal single crystals with a pulsed nuclear magnetic resonance apparatus at both room and liquid nitrogen- temperatures. The values obtained for aluminum and vanadium agreed well with the values given in the literature for powdered samples. The niobium value was slightly lower than the most reliable powder value, possibly because of impurities. Measurements were made on isotopically pure tin to see if any anisotropy could be detected in the spin-lattice relaxation time. No anisotropy could be detected, but the crystal orientation used was so unfavourable that an anisotropy of less than about 50% could not be detected. The spin-spin relaxation time was measured in the isotopically pure tin for five different magnetic field orientations. These showed that exchange narrowing occurred. With a suitable choice of operating conditions, the apparatus measured the equivalent of the absorption mode in steady state nuclear magnetic resonance as a function of magnetic field orientation. This was combined with the spin-spin measurements to give the complete orientation dependence of the latter. These measurements gave a value of (2.1±0.3)Kc/s. for the pseudo-exchange constant in tin. The pseudo-dipolar second moment was found to be twice the dipolar second moment. Spin echoes were observed in the isotopically pure tin and were used to measure the spin-spin relaxation time. These gave values which were much shorter than those measured by free induction decays. The reason for this was not determined. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A new method of synthesizing organic fluorides stereospecifically was developed; the elements 'BrF' and 'IF' were added quantitatively across the double bond of simple olefins such as cyclohexene, using elemental halogen and silver fluoride at room temperature in benzene. Application of this reaction to the activated olefin, acenaphthylene, resulted in a variety of products, depending on solvent; with pure acetonitrile solvent, quantitative 'BrF' addition occurs, but with an increasing proportion of benzene various side reactions take place, including difluorination and dimerization. Another series of compounds was synthesized from fluoro- acenaphthylene by various addition and substitution reactions, and all together fifteen acenaphthene fluorides were made, including thirteen new compounds. The ¹H and ¹⁹F N.M.R. spectra of these substances were measured and a set of ³JHF values obtained for a wide variation in the electronegativity of the substituents, and for two values of dihedral angle (0°and 100°). This data showed that the dependence of ³JHF upon electronegativity was far from linear, as had hitherto been supposed, but rather exponential, which is in retrospect more logical. Application of this data on ³JHF to some flexible systems, derivatives of indene and benzofuran, allowed their conformations to be determined. In all cases the pucker of the five-membered ring is small (∼25°), except in the cis-bromofluoride of benzofuran where it is much larger, (45-50°). A separate study was made of the conformational inversion of trans-1-fluoro-2-iodocyclohexane (I) and its specifically deuterated analogue, derived from 3,3,6,6-tetradeutero-cyclohexene. Several methods were employed to measure the position of the conformational equilibrium and this permitted a comparison of the methods themselves. It was found that all chemical shifts and coupling constants were temperature dependent, those involving ¹⁹F being particularly susceptible. The only reliable methods were found to be area measurements (at -90°C), linewidth measurements (at -45°C), and temperature-corrected ¹⁹F chemical shift measurements; thus the compound in question was found to have a preference for the diequatorial form, with ∆G° = 0.650 ± 0.025 kcal./mole (at -90°C to 0°C), and a near zero entropy, ∆S° = 0.0 ± 0.5 e.u. This value of ∆G° is only 0.1 kcal./mole smaller than the sum of the A-values for iodine and fluorine, and indicates that the repulsion between these two halogens in the diequatorial form is quite small, about one tenth that between iodine and chlorine, or between chlorine and chlorine, etc. A kinetic study of I was made by applying the general lineshape equation of Gutowsky and Holm for two-site exchange; calculated line-widths and positions were matched to the experimental ¹⁹F spectra (with all ¹H couplings removed by irradiation) at various temperatures, and thus an Arrhenius plot was made and activation parameters derived. ∆FƗ = 10.38 kcal./mole; ∆SƗ = 2.1 e.u. / Science, Faculty of / Chemistry, Department of / Graduate

The work described in this thesis was initiated in an attempt to overcome the limitations imposed upon NMR spectroscopy by magnetic field inhomogeneity in two specific areas: high resolution spectroscopy in isotropic liquids, and chemical shift resolved NMR imaging in isotropic liquids. In both cases magnetic field inhomogeneity may degrade the resolution of spectra to such an extent that no useful information can be obtained from them. In high resolution NMR spectroscopy it is necessary to be able to extract accurately the parameters present within the spectrum such as chemical shifts, coupling constants and peak areas. In chemical shift resolved imaging experiments the requirements are less stringent; and it is only necessary that the resonances of different chemical species be resolved. However, even the less stringent requirements of NMR imaging are often difficult to meet as the sample volumes required are often several orders of magnitude larger than those required in conventional high resolution NMR spectroscopy. The use of zero-quantum coherence has been investigated as a potential solution to the magnetic field inhomogeneity problem in both of these areas. Zero-quantum coherences are independent of magnetic field inhomogeneity and contain the parameters desired in both cases, though they are displayed in a way which differs from conventional NMR spectra. In this thesis, existing zero-quantum coherence experiments have been evaluated for use with inhomogeneous magnetic fields, and, where necessary, adapted for this purpose. Several completely new experiments have been developed for producing broad-band decoupled zero-quantum coherence spectra and also for presenting coupling constants and chemical shifts in a manner which is as close to conventional NMR spectra as possible, hence facilitating ease of use. Zero-quantum coherence has been evaluated as a tool for identifying unknown compounds and also for identifying the components of complex mixtures by "signature" recognition. Both decoupled and non-decoupled zero-quantum coherence experiments are adapted to provide imaging experiments which allow the separation of the images of different chemical species in inhomogeneous magnetic fields. The two-dimensional J-resolved experiment is also adapted for this purpose. / Science, Faculty of / Chemistry, Department of / Graduate

The work described in this thesis is divided into two parts: testing and evaluation of some surface coils, and application of the surface coils to in-vivo studies. In particular, the localization properties of surface coils were examined and optimized using the highest performance coil geometry and wire. Application of the surface coil technique to in-vivo studies involved measuring changes in metabolic status of muscle and brain tissue in rats using ³¹P spectroscopy. The properties of surface coils have been studied by evaluating their excitation patterns with ¹H and ³¹P NMR spectroscopy. Surface coils, manufactured in different sizes, geometries, and materials were tested for Q factors, signal-to-noise ratios, and pulse widths required for excitation of the sample. A silver plating on the copper wire used to fabricate the surface coils was found to increase the Q and signal-to-noise of the coil. Examination of the excitation patterns of the surface coils with point samples characterized the B₁ field of the coils as decreasing axially and radially from the coil. Calculations of the magnitude of the B₁ field reveal that its dome-like shape extends to approximately one coil radius above the surface coil. It was found that samples lying outside the domain of this "sensitive volume" did not contribute to a spectrum. These data were all correlated and the "0.9" silver plated coil was deemed to be the most efficient coil with which to pursue further in-vivo studies. In-vivo ³¹P studies of rat tissues were preceded by in-vitro spectral measurements of various metabolites at physiological concentrations. These standards were used to aid in the identification of resonances in the in-vivo spectra. Metabolic changes such as artificially induced ischemia in muscle, deceased brain, and artificially induced brain dementia were compared with "normal" ³¹P spectra of anaesthetized rat tissues. It was found that oxygen deprivation is readily observed with this technique whereas the preparation of brain dementia cannot be diagnosed with ³¹P NMR spectroscopy. / Science, Faculty of / Chemistry, Department of / Graduate