[PDF] Solid State Nuclear Magnetic Resonance Of Exotic Quadrupolar Nuclei As A Direct Probe Of Molecular Structure In Organic Ionic Solids eBook

Author : Kevin Burgess
Publisher :
Page : pages
File Size : 23,6 MB
Release : 2015
Category : University of Ottawa theses
ISBN :

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In the past decade, the field of NMR spectroscopy has seen the emergence of ever more powerful superconducting magnets, which has opened the door for the observation of many traditionally challenging or non-receptive nuclei. In this dissertation, a variety of ionic solids with organic coordination environments are investigated using quadrupolar solid-state NMR experiments with an ultrahigh-field magnet (21.1 T). Two general research directions are presented including a 79/81Br solid-state NMR study of a series of 6 triphenylphosphonium bromides for which single-crystal X-ray structures are reported herein. A second research direction is also presented wherein alkaline-earth metal (25Mg, 43Ca, and 87Sr) solid-state NMR is used to characterize a systematic series of 16 aryl and alkyl carboxylates. In both studies, the quadrupolar nuclei studied are deemed zexoticy due to their unreceptive nature to NMR spectroscopic analysis including low natural abundances, large quadrupole moments, or low resonance frequencies. A variety of coordination modes to alkaline-earth metals, including N-atom coordination, are characterized herein for the first time using alkaline-earth metal solid-state NMR. In all cases, the electric field gradient (EFG) and chemical shift (CS) tensors are characterized and correlated to structural features such as interatomic distances measured from the crystal structure of the compound under study. In all of the projects undertaken herein, the gauge-including projector-augmented-wave density functional theory (GIPAW DFT) method is used, which allows for the prediction and rationalization of the experimental EFG and CS tensor parameters based on the input crystal structure. In the case of 43Ca solid-state NMR experiments reported in this dissertation, a linear correlation between the calculated and experimental 43Ca quadrupolar coupling constants, CQ, is used as a calibration curve for GIPAW DFT calculations performed on the 18 structural models currently available for the vaterite polymorph of CaCO3. Vaterite cannot be fully characterized by X-ray diffraction alone; therefore an NMR crystallography protocol is used in order to identify the model that best accounts for 43Ca solid-state NMR experiments performed on vaterite. It is expected that the conclusions from this dissertation can be used for future studies involving structural refinement and elucidation of solid materials containing challenging quadrupolar nuclei.

Author : Alexandra Faucher
Publisher :
Page : 234 pages
File Size : 12,40 MB
Release : 2016
Category : Exotic nuclei
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This thesis is concerned with NMR studies of solids containing NMR-active quadrupolar nuclei typically overlooked due to their unfavorable NMR properties, particularly moderate to large nuclear electric quadrupole moments. It is shown that 75As, 87Sr, and 121/123Sb NMR spectra of a wide range of solid materials can be obtained. Traditional 1D pulse sequences (e.g., Bloch pulse, spin echo, QCPMG) are used alongside new methods (e.g., WURST echo, WURST-QCPMG) to acquire the NMR spectra; the advantages of these new methods are illustrated. Most of these NMR spectra were acquired at an external magnetic field strength of B0 = 21.14 T. Central transition (mI = 1/2 to -1/2) linewidths of half-integer quadrupolar nuclei of up to a breadth of ca. 32 MHz are obtained at B0 = 21.14 T, demonstrating that nuclear sites with large nuclear quadrupolar coupling constants can be characterized. Many of the NMR spectra contained in this research depict situations in which the nuclear quadrupolar interaction is on the order of or exceeds the magnitude of the Zeeman interaction, thus rendering the high-field approximation invalid and requiring exact treatment in which the full Zeeman-quadrupolar Hamiltonian is diagonalized in order to properly simulate the NMR spectra and extract NMR parameters. It is also shown that both direct (Reff) and indirect (J) spin-spin coupling between quadrupolar nuclei can be quantified in some circumstances, and that the signs of the isotropic indirect spin-spin coupling and the nuclear quadrupolar coupling constants can be obtained experimentally in cases of high-field approximation breakdown. This research represents a relatively large and valuable contribution to the available 75As, 87Sr, and 121/123Sb NMR data in the literature. For example, experimentally determined chemical shift anisotropy is reported for the 87Sr nucleus in a powdered solid for the first time, and the NMR parameters for 11B-75As spin-spin coupling constants reported here add to a sparse collection of information on quadrupolar spin-pairs. Overall, this research is a step towards the goal of utilizing the entire NMR periodic table for the characterization of molecular and crystallographic structure as well as structural dynamics.

Author : Jerry C. C. Chan
Publisher : Springer
Page : 328 pages
File Size : 12,45 MB
Release : 2011-10-12
Category : Science
ISBN : 3642248039

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Dipolar Recoupling, by Niels Chr. Nielsen, Lasse A. Strassø and Anders B. Nielsen.- Solid-State NMR Techniques for the Structural Determination of Amyloid Fibrils, by Jerry C. C. Chan.- Solid-State 19F-NMR of Peptides in Native Membranes, by Katja Koch, Sergii Afonin, Marco Ieronimo, Marina Berditsch and Anne S. Ulrich.- Probing Quadrupolar Nuclei by Solid-State NMR Spectroscopy: Recent Advances, by Christian Fernandez and Marek Pruski.- Solid State NMR of Porous Materials Zeolites and Related Materials, by Hubert Koller and Mark Weiß.- Solid-State NMR of Inorganic Semiconductors, by James P. Yesinowski.-

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Publisher :
Page : pages
File Size : 45,47 MB
Release : 2003
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This dissertation describes recent developments in solid state nuclear magnetic resonance (NMR), for the most part involving the use of dynamic-angle spinning (DAS) NMR to study quadrupolar nuclei. Chapter 1 introduces some of the basic concepts and theory that will be referred to in later chapters, such as the density operator, product operators, rotations, coherence transfer pathways, phase cycling, and the various nuclear spin interactions, including the quadrupolar interaction. Chapter 2 describes the theory behind motional averaging experiments, including DAS, which is a technique where a sample is spun sequentially about two axis oriented at different angles with respect to the external magnetic field such that the chemical shift and quadrupolar anisotropy are averaged to zero. Work done on various rubidium-87 salts is presented as a demonstration of DAS. Chapter 3 explains how to remove sidebands from DAS and magic-angle spinning (MAS) experiments, which result from the time-dependence of the Hamiltonian under sample spinning conditions, using rotor-synchronized[pi]-pulses. Data from these experiments, known as DAH-180 and MAH-180, respectively, are presented for both rubidium and lead salts. In addition, the applicability of this technique to double rotation (DOR) experiments is discussed. Chapter 4 concerns the addition of cross-polarization to DAS (CPDAS). The theory behind spin locking and cross polarizing quadrupolar nuclei is explained and a method of avoiding the resulting problems by performing cross polarization at 0[sup o] (parallel) with respect to the magnetic field is presented. Experimental results are shown for a sodium-23 compound, sodium pyruvate, and for oxygen-17 labeled L-akmine. In Chapter 5, a method for broadening the Hartmann-Hahn matching condition under MAS, called variable effective field cross-polarization (VEFCI?), is presented, along with experimental work on adamantane and polycarbonate.