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Improved 13 C 1 H shift correlation spectra for indirectly bonded carbons and hydrogens: The FLOCK sequence
Author(s) -
Reynolds William F.,
McLean Stewart,
PerpickDumont Marion,
Enríquez Raül G.
Publication year - 1989
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.1260270214
Subject(s) - chemistry , pulse sequence , spectral line , polarization (electrochemistry) , sequence (biology) , coupling constant , analytical chemistry (journal) , molecular physics , nuclear magnetic resonance , physics , organic chemistry , biochemistry , particle physics , astronomy
Several modifications of the basic 13 C 1 H shift correlation sequence as optimized for polarization transfer via long‐range 13 C 1 H coupling constants are described and evaluated. Modifications involve incorporation of BIRD pulse(s) at the mid‐point of the evolution period and/or at the mid‐point of the fixed delay prior to polarization transfer, in addition to the previously discussed incorporation of a BIRD pulse during the final fixed delay. These modifications give significantly improved sensitivity for many cross‐peaks, excellent suppression of one‐bond peaks and, in the case of the sequence incorporating two additional BIRD pulses, some ability to distinguish two‐bond and three‐bond connectivity peaks. The latter sequence is, overall, comparable in sensitivity to the fixed time sequences XCORFE and COLOC. It is also easier to parameterize and gives better suppression of one‐bond peaks and other artifacts.