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Long‐range 19 F– 15 N heteronuclear shift correlation: examination of J ‐modulations associated with broad range accordion excitation
Author(s) -
Russell David J.,
Hadden Chad E.,
Martin Gary E.,
Krishnamurthy Krish
Publication year - 2002
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.992
Subject(s) - heteronuclear molecule , chemistry , range (aeronautics) , pulse sequence , analytical chemistry (journal) , amplitude , excitation , two dimensional nuclear magnetic resonance spectroscopy , spectral line , correlation function (quantum field theory) , atomic physics , molecular physics , nuclear magnetic resonance , nuclear magnetic resonance spectroscopy , physics , stereochemistry , optics , quantum mechanics , materials science , chromatography , dielectric , composite material
The first demonstrated example of 19 F– 15 N long‐range heteronuclear shift correlation spectroscopy at natural abundance is reported. Because of the very large variation in the size of 2 J (N,F) vs 3 J (N,F) long‐range heteronuclear couplings, the utilization of one of the new accordion‐optimized long‐range heteronuclear shift correlations experiments is essential if all possible correlations are to be observed in a single experiment. A modified IMPEACH‐MBC pulse sequence was used in conjunction with an optimization range from 4 to 50 Hz to demonstrate the technique using a mixture of 2‐ and 3‐fluoropyridine, which had 2 J (N,F) and 3 J (N,F) long‐range couplings of −52 and 3.6 Hz, respectively. Because of the size of the 2 J (N,F) long‐range coupling constant, a J ‐modulation of the long‐range correlation response is observed in the spectrum resulting in a ‘doublet’ in F 1 due to amplitude modulation. The size of the ‘doublet’ is shown to be a function of the parameter selection ( t 1max , T max , T min and spectral width in F 1 ). This behavior is similar to F 1 ‘skew’ associated with long‐range correlation responses in ACCORD‐HMBC spectra which has been analyzed in detail previously. Copyright © 2002 John Wiley & Sons, Ltd.