Doctor of Philosophy (Ph.D.)
Solid state deuteron NMR experiments, especially magic angle spinning (MAS) and off-magic angle spinning (OMAS), are developed to explore dynamical systems. A theoretical discussion of interactions relevant for spin-1 nuclei is presented. Practical aspects of MAS/OMAS experiments are described an detail. The dominant quadrupolar coupling interaction in deuteron NMR has been simulated and the effects of multiple-frame molecular motions on MAS/OMAS spectra are taken into account in this calculation. Effects of chemical shift anisotropy are also simulated, and shown to be small under conditions of rapid sample spinning.;Two numerical methods, direct integration and an efficient simulation routine based on Floquet thoery, are discussed. Improvements in computational efficiency of the Floquet method in computing solid stae deuteron MAS/OMAS spectrum makes the quantitative analysis of molecular motion possible: complex multiple frame molecular motions, deuteron quadrupolar interactions and chemical shift anisotropy are now included in a single simulation routine and the effects of the multiple-frame molecular motions can be analyzed by comparing the line shapes of simulations with those of experiments.;The enhanced motional sensitivity of deuteron NMR MAS/OMAS makes it possible to detect temperature-dependent motion rates of urea molecules in octanoic acid/urea inclusion compounds. Temperature-dependent deuteron OMAS line shapes have been recorded and fitted through least-square procedures, to provide rates of rotation about both CN and CO bonds. Activation energies have been calculated for these motions. The power and utility of OMAS is demonstrated by this investigation.;The phenyl ring motions in appropriately labeled L-phenylalanine and N-acetyl-L-phenylalanine methyl ester/cyclodextrin inclusion compound have also been studied through high field deuteron MAS experiments. Phenylalanine MAS spectra with ultra-fast ring-flip motion have been simulated and the range of phenyl ring flip rates is obtained by comparing the simulated and experimental spectra. In the studies of phenylalanine/cyclodextrin inclusion compound, an approach to a physically reasonable diffusion model has also been made by increasing the number of jump sites per unit solid angle included in the calculation. These simulations involve repeated diagonalization of very large matrices and demonstrate the capability of the approach to handle complex dynamical systems.
© The Author
Huang, Yuanyuan, "Effects of molecular motion on deuteron magic angle spinning NMR spectra" (2007). Dissertations, Theses, and Masters Projects. Paper 1539623519.