Physical
and Biophysical Chemistry Division (I)
Further Conventions for NMR Chemical Shifts
IUPAC has published a number of recommendations regarding
the reporting of nuclear magnetic resonance (NMR) data, especially chemical
shifts. The most recent publication [Pure
Appl. Chem.
73, 1795-1818 (2001)] recommended that tetramethylsilane
(TMS) serve as a universal reference for reporting the shifts of all
nuclides, but it deferred recommendations for several aspects of this
subject. This document first examines the extent to which the shielding
in TMS itself is subject to change by variation in temperature, concentration,
and solvent. On the basis of recently published results, it has been
established that the shielding of TMS (along with that of DSS, often
used as a reference for aqueous solutions) varies only slightly with
temperature but is subject to solvent perturbations of a few tenths
of a ppm. Recommendations are given for reporting chemical shifts under
most routine experimental conditions and for quantifying effects of
temperature and solvent variation, including the use of magnetic susceptibility
corrections and of magic-angle spinning (MAS).
This document provides the first IUPAC recommendations
for referencing and reporting chemical shifts in solids, based on high-resolution
MAS studies. Procedures are given for relating 13C
NMR chemical shifts in solids to the scales used for high-resolution
studies in the liquid phase. The notation and terminology used for describing
chemical shift and shielding tensors in solids is reviewed in some detail,
and recommendations are given for best practice.
> Download full text of the Provisional Recommendations (pdf
file - 770KB)
Comments by 31 May 2007
Prof. Robin K. Harris
University of Durham
Department of Chemistry
South Road
Durham, DH1 3LE
United Kingdom
TEL: +44 (191) 374 3121
FAX: +44 (191) 384 4737
E-MAIL: [email protected]
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