The performance of deuterium−carbon correlation
(DECOR) spectroscopy for the assignment and measurement
of deuterium quadrupolar couplings in fully deuterated liquid
crystalline phases is analyzed. The experiment
relies on a broadband polarization transfer step from deuterium to
carbons. The efficiency of this step is
demonstrated experimentally together with a brief study of
cross-polarization dynamics. We show that
resolution can be improved by removing the substantial contributions
from heteronuclear dipolar couplings
in a refocused version of the experiment. Quantification of the
quadrupolar couplings is illustrated by the
application to the thermotropic liquid crystal 5CB. A complete
assignment is obtained by using both short-range and long-range correlations, allowing the individual measurement
of all the aromatic couplings that are
overlapping in the one-dimensional deuterium spectrum. The
heteronuclear C−D couplings are shown to be
measurable by direct inspection of the 2D spectra. By way of
demonstration, we show that the experiment
allows the measurement of quadrupolar couplings as a function of
temperature.
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