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sup 13 C- sup 31 P cross polarization between isolated spin pairs in organophosphorus substances: Intramolecular structure and internuclear distance determinations in spinning solids

Journal Article · · Journal of the American Chemical Society; (USA)
DOI:https://doi.org/10.1021/ja00177a001· OSTI ID:6226266
Cross polarization between dilute effectively isolated {sup 13}C-{sup 31}P spin pairs provides a unique method to examine selectively the microenvironment around the phosphorus atom in organophosphorus substances. Strong oscillations occur during cross polarization between these isolated spin pairs in MAS experiments on microcrystalline powders. The oscillation frequency is proportional to the {sup 13}C-{sup 31}P dipolar interaction and hence allows specific internuclear distance determinations on powder samples. Maximum carbon signal intensity and experimental simplicity are achieved in double cross polarization (DCP)/MAS {sup 13}C NMR experiments that impose a short T{sub 1p} on the {sup 31}P magnetization by {sup 31}P radio frequency phase modulation. This experimental stratagem suppresses cross-polarization oscillations and yields simple exponential kinetics for the transfer process. It also relaxes the tolerance on the match condition and MAS speed for cross polarization between weakly coupled dipole pairs.
DOE Contract Number:
AC05-84OR21400
OSTI ID:
6226266
Journal Information:
Journal of the American Chemical Society; (USA), Journal Name: Journal of the American Chemical Society; (USA) Vol. 112:21; ISSN 0002-7863; ISSN JACSA
Country of Publication:
United States
Language:
English