Date of Award
Chemistry and Biochemistry
Schurko, Robert (Chemistry and Biochemistry)
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Nuclei are termed unreceptive if they are not amenable to solid-state NMR (SSNMR) experimentation at standard magnetic field strengths due to (i) low natural abundances or dilution; (ii) low gyromagnetic ratios; (iii) inefficient longitudinal relaxation; (iv) large quadrupole moments; or (v) combinations of these factors. This thesis focuses on applying a variety of SSNMR methods to study unreceptive nuclei in a variety of systems. The first portion of this thesis focuses upon ultra-wideline (UW) SSNMR of three main group nuclei: 209Bi, 137Ba and 115In. 209Bi and 137Ba SSNMR were applied to a series of systems with important structural motifs, while 115In SSNMR was applied to systems with In in the +1 oxidation state. Extremely broad SSNMR spectra were acquired at field strengths of 9.4 and 21.1 T. In all cases, the electric field gradient (EFG) and the chemical shift (CS) tensor parameters obtained from these spectra are used to probe the metal coordination environments. These data are complemented by first principles calculations of the NMR tensors using molecular orbital (MO) and plane wave density functional theory (DFT) methods. The second portion of this thesis examines applications of SSNMR of unreceptive nuclei to some practical problems. First, 109Ag and 15N SSNMR experiments were performed to study silver supramolecular frameworks, and structural changes which occur upon their reactions with primary amines. 1H-109Ag cross polarization/magic-angle spinning (CP/MAS) NMR spectra were used to differentiate Ag sites, and 1H-15N CP/MAS NMR spectra provided measurements of 1J(109Ag, 15N) coupling constants, which are used to probe bonding Ag-N bonding. First principles calculations of silver and nitrogen CS tensors and 1J(109Ag, 15N) constants aided in formulating the structural models for the new materials. Second, 35Cl SSNMR spectra, single-crystal and powder X-ray diffraction data, and ab initio calculations were utilized to study HCl pharmaceuticals and some of their polymorphs. The sensitivity of the 35Cl EFG tensor parameters to subtle changes in the chlorine environments is reflected in the powder patterns, which can be used for structural interpretation, identifying and distinguishing polymorphs, and rapidly providing a spectral fingerprint of each pure pharmaceutical and its polymorphs.
Hamaed, Hiyam, "Solid-State NMR Spectroscopy of Unreceptive Nuclei in Inorganic and Organic Systems" (2010). Electronic Theses and Dissertations. 391.