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Carbon NMR chemical shit tensors are measured for two forms of solid 10-deacetyl baccatin lll to find out more about the origins of solid-state NMR shift differences in polymorphs. Tensor differences that were observed seem to be basically because of conformational variations in ring substituents and the cyclohexenyl ring.

Research was conducted to examine the application of the PHORMAT and FIREMAT solid-state NMR analyses to the terpene parthenolide to obtain all shift tensors. A comparison of the two sets of principal values can be carried out statistically to estimate the precision in the tensor measurements after having determined the tensors from both approaches. The assignments were given for all carbons and it was observed for the first time that most of the carbons may be assigned to one or the other of the two distinct molecules in the crystallographic asymmetric unit.

A study using single-crystal X-ray diffraction and solid-state 15N NMR spectroscopy examined an azobenzene dyestuff which goes through conformational exchange in the solid state. The combined utilization of the two techniques provided a thorough understanding of the disordered character of a common azobenzene dyestuff. The X-ray analysis demonstrated two conformations with an almost equal weighting within the asymmetric unit. Meanwhile, solid-state NMR showed that a motional process that interconverted two trans conformations on a time scale influenced the quality of the disorder.

McGeorge is an experienced analytical scientist with more than 13 years of industrial experience. He has led various projects in the area of PAT, noninvasive method development, materials characterization, and [...]

Two different crystalline polymorphs of valinomycin, the triclinic and monoclinic forms, have been studied by high resolution, solid state 13C CP-MAS NMR spectroscopy. Although the two polymorphs of the crystal are remarkably similar, there are distinct differences in the isotropic chemical shifts between the two spectra. For the triclinic form, the carbon chemical shift tensor components for the alpha carbons adjacent to oxygen in the lactic acid and hydroxyisovaleric acid residues and the ester carbonyls of the valine residue were obtained using the FIREMAT experiment. From the measured components, it was found that the behavior of the isotropic chemical shift, δiso, for valine residue ester carbonyl carbons is predominately influenced by the intermediate component, δ22. Additionally it was found that the smallest shift component, δ33, for the L-lactic acid (L-Lac) and D-α-hydroxyisovaleric acid (D-Hyi) Cα -O carbon was significantly displaced depending upon the nature of individual amino acid residues, and it is the δ33 component that governs the behavior of δiso in these alpha carbons. [ABSTRACT FROM AUTHOR]

Presents a study which described the application of PHORMAT and FIREMAT solid-state nuclear magnetic resonance (NMR) techniques in analyzing shift values in terpene parthenolide. Explanation of the NMR analysis techniques; Methodology used; Results and discussion; Conclusion.

Reports on the measurement of carbon nuclear magnetic resonance (NMR) chemical shift tensors for two forms of solid 10-deacetyl baccatin III to investigate the origins of solid-state NMR. Finding that lattice interactions cannot fully account for the shift differences in the two forms; Possible appearance of the observed tensor differences from conformational variations in ring substituents.