This thesis describes double-resonance solid-state NMR connectivity experiments
involving quadrupolar and spin-1/2 nuclei. Cross-polarization, transferred-echo double-resonance
(TEDOR), rotational-echo double-resonance (REDOR), and dipolar-dephasing
difference experiments were used to determine connectivities via the heteronuclear dipolar-couplings
between quadrupolar and spin-1/2 nuclei. Two-dimensional extensions of the
cross-polarization and TEDOR experiments reveal connectivities between specific
resonances in two-dimensional correlation spectra.
Cross-polarization experiments were performed between 27Al and 31P nuclei in the
aluminophosphate molecular sieves VPI-5 and AIPO4-8, and an experimental investigation
of the parameters controlling the efficiency of the transfer is presented. REDOR, TEDOR,
and dipolar-dephasing difference experiments are also demonstrated.
Increased efficiency in cross-polarization experiments involving quadrupolar nuclei
is obtained between 27Al and 31P spins in VPI-5 by carrying out the cross-polarization step
with the spinning axis parallel to the applied magnetic field. After the cross-polarization
step, the spinning axis is rapidly switched to the "magic angle" for detection of the high-resolution
signal.
The experiments developed for 27Al and 31P nuclei were extended to 27Al and 29Si
nuclei for a series of representative zeolite frameworks, in which there is a relative
enhancement of a given Si resonance which is approximately linear with the number of
aluminum atoms in the neighbouring tetrahedral sites. Further extensions of the techniques
to include 11B, 23Na, and 29Si nuclei are demonstrated for borosilicate glasses.
The 27Al/ 31P and 27Al/29 Si connectivity experiments were used to determine the
method of silicon substitution and reveal the presence of three types of aluminum
environments in the sihcoaluminophosphate molecular sieve SAPO-37. The experiments.
were also applied to the aluminophosphate AIPO4-5, confirming that the octahedral
aluminum formed upon hydration remains bonded in the framework.
For the first time, INEPT and DEPT experiments were performed in the solidstate.
These experiments utilize coherence-transfer based on heteronuclear J-couplings to
detect through-bond connectivities. Examples presented show that the experiments are
applicable to both quadrupolar and spin-1/2 nuclei, and that only the +1/2 energy levels of
the quadrupolar nuclei are involved in the coherence transfer. / Science, Faculty of / Chemistry, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/6206 |
| Date | 05 1900 |
| Creators | Wong-Moon, Kirby Charles |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Format | 12242369 bytes, application/pdf |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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