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Title: Solid-state NMR measurements of proton chemical shift anistropies
Author: Miah, Habeeba Khatun
ISNI:       0000 0004 6352 0054
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2016
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A new isotropic-anisotropic correlation experiment has been designed. This combines ultrafast magic angle spinning (MAS) at rates up to 80 kHz for good resolution of isotropic sites with a symmetry-based recoupling sequence to reintroduce the chemical shift anisotropy (CSA) in the indirect dimension. The experiment was implemented for protons at a Larmor frequency of 600 MHz, with some further development at a higher field corresponding to 850 MHz. The experiment was also successfully extended to the case of 19F CSAs. The CSA can be extracted by fitting the resulting lineshapes when the isotropic line is resolved in the direct dimension. The effects of couplings to abundant heteronuclei have also been investigated, since the sequences also recouple the heteronuclear dipolar coupling in certain circumstances. In this case both the dipolar coupling constant and the CSA can be extracted by fitting the resulting lineshapes. Alternatively, the dipolar coupling can be removed, using a dual-channel version of the experiment, to leave only the CSA. CASTEP has been used, in conjunction with experimental results, to refine the X- ray crystal structures of a variety of systems. The success of the refinement process depends on the presence of accurate heavy atom positions since this has a large effect on the calculated *H NMR parameters. A secondary aim was to investigate the correlation between proton CSAs and hydrogen bond lengths. Plotting the optimised hydrogen bond lengths and the corresponding calculated anisotropies revealed linear relationships dependent on the nature of the hydrogen bond acceptors and donors. In contrast, the relationship between the isotropic shifts and hydrogen bond lengths was found to be less linear than previously proposed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available