13C CP MAS NMR of halogenated (Cl,Br, I) pharmaceuticals at ultrahigh magnetic fields |
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Authors: | Victor V Terskikh Stephen J Lang Peter G Gordon Gary D Enright John A Ripmeester |
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Institution: | 1. Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, Canada K1A 0R6;2. Department of Chemistry, Carleton University, Ottawa, Canada K1S 5B6 |
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Abstract: | This work reports significantly improved spectral resolution of 13C CP MAS NMR spectra of chlorinated, brominated and iodinated solid organic compounds when such spectra are recorded at ultrahigh magnetic field strengths. The cause of this is the residual dipolar coupling between carbon atoms and quadrupolar halogen nuclides (chlorine‐35/37, bromine‐79/81 or iodine‐127), an effect inversely proportional to the magnetic field strength which declines in importance markedly at 21.1 T as compared to lower fields. In favorable cases, the fine structure observed can be used for spectral assignment, e.g. for Cl‐substituted aromatics where the substituted carbon as well as the ortho‐carbons show distinct doublets. The experimental results presented are supported by theoretical modeling and calculations. The improved spectral resolution in the studied systems and similar halogenated materials will be of particular interest and importance for polymorph identification, drug discovery and quality control in the pharmaceutical industry. Copyright © 2009 John Wiley & Sons, Ltd. |
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Keywords: | solid‐state NMR ultrahigh magnetic field 13C CP MAS halogenated compounds chlorinated brominated iodinated pharmaceuticals drugs |
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