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13 C CP MAS NMR of halogenated (Cl, Br, I) pharmaceuticals at ultrahigh magnetic fields
Author(s) -
Terskikh Victor V.,
Lang Stephen J.,
Gordon Peter G.,
Enright Gary D.,
Ripmeester John A.
Publication year - 2009
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2399
Subject(s) - chemistry , halogen , bromine , chlorine , nmr spectra database , halogenation , spectral line , carbon fibers , analytical chemistry (journal) , dipole , organic chemistry , alkyl , physics , materials science , astronomy , composite number , composite material
This work reports significantly improved spectral resolution of 13 C 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.