Webber, Amy Louise (2010) Probing intermolecular interactions and three-dimensional packing of organic molecules by solid-state NMR. PhD thesis, University of Warwick.

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Abstract

Identifying the ordered three-dimensional structures formed by atoms and molecules is essential to understanding the properties of solid-state materials. Solid-state NMR is an extremely sensitive structural probe and offers atomic-level information regarding the three-dimensional packing of molecules and the intermolecular interactions, for example, hydrogen bonding, which control this. Recently, the combination of advanced solid-state NMR experiments and complementary computational techniques have led to the emergence of the field of `NMR crystallography', which shows great potential for the structural determination of systems where traditional diffraction-based methods are not suitable. The work in this thesis uses a combined approach of high-resolution MAS NMR experiments and first-principles (GIPAW) calculations of NMR parameters to provide structural insight into a range of challenging organic systems. In particular, 1H-13C and 1H DQ (double-quantum) CRAMPS (combined rotation and multiple pulse spectroscopy) techniques are employed to identify 1H and 13C NMR chemical shifts and close 1H-1H interatomic proximities. A new 1H DQ-13C SQ (single-quantum) experiment is presented that better allows intra- and intermolecular 1H-1H distances to be identified in the pharmaceutical compound, penicillin and the disaccharide, β-maltose monohydrate, notably enabling, for the first time, the full 1H resonance assignment of the latter. Using a similar methodology, a `spectrum to structure' approach is applied to identify modes of self assembly for guanosine derivatives for which single-crystal diffraction structures could not be obtained. In addition, chemical shift calculations on the full unit cell (348 atoms) of a complex pyrazole allow the complete assignment of experimental 1H, 13C resonances for each of the six independent molecules of the asymmetric unit cell. Finally, hydrogen-bond mediated 2hJ15N17O and 2hJ15N13C couplings across NH...O and N...HC hydrogen bonds are determined experimentally for the first time by the use of heteronuclear spin-echo experiments. The J couplings, which have also been determined using first-principles calculations, are a quantitative measure of hydrogen-bonding strength.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QC Physics
Library of Congress Subject Headings (LCSH):	Nuclear magnetic resonance, Solid state physics, Chemical structure
Date:	March 2010
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Brown, Steven P.
Sponsors:	Engineering and Physical Sciences Research Council (EPSRC) ; European Union (EU) (EU-NMR)
Extent:	xv, 196, 16 leaves : ill., charts
Language:	eng
URI:	http://wrap.warwick.ac.uk/id/eprint/3814

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