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|Title:||Applications of Nuclear Quadrupole Double Resonance Spectroscopy|
|Author(s):||Woyciesjes, Peter Michael|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Nuclear Quadrupole Resonance (NQR) spectroscopy measures the interaction of a nucleus possessing an electric quadrupole moment Q with the electric field gradient (efg) produced at the nucleus by its local electronic environment. As a result, the NQR technique provides information on the ground state charge distribution in the vicinity of the quadrupolar nucleus.
In this work the ('14)N and ('17)O NQR spectra for a series of substituted aromatic amine oxides were utilized to probe the electronic nature of the N-O group. With the aid of CP-MAS ('13)C NMR the orientation of the ('14)N efg tensor was determined. The Z axis of the ('17)O efg tensor was determined to be coincidental to the N-O bond. Using a modified Townes-Dailey model, analysis of the hydrogen bonding, coordination, and ring substituent effects on the nature of the N-O group are interpreted in terms of changes in the nitrogen and oxygen valence p orbital populations. The NQR results also provide a quantitative measure of the sensitivity of the pi-bond order to variations in the para substituent. Changes in the solid state N-O pi-bond order correlates well with N-O stretching frequencies and ('17)O and ('15)N NMR chemical shifts.
The ('2)H and ('14)N NQR spectra for a series of urea adducts were studied to develop a better understanding of the nature and extent of charge transfer that occurs in the peptide linkage, -CONH(,2), upon the formation of N-H---O and O-H---O hydrogen bonds. Crystallographic data indicates the presence of dramatic variations in the electronic structure of the amide framework with varying hydrogen bond strengths. The ('2)H and ('14)N NQR data provides quantitative measures of electronic changes as well as the variations in valence shell orbital populations that occur with changing hydrogen bonding character.
In the last section the ('2)H NQR spectra were obtained for a series of inorganic and organic crystal hydrates. The ('2)H NQR spectrum for water of hydration appear to fall into three categories, one which is characterized by a six-line multiplet (nu)(,+) and (nu)(,-) ('2)H pattern and two which give rise to two separate (nu)(,+) and (nu)(,-) peaks.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.
|Date Available in IDEALS:||2014-12-15|