The 2D Fully-Coupled (FUCOUP) experiment is the simplest
2D heteronuclear chemical-shift correlation experiment based on carbon
detection. Presently, its application is very limited.
REQUIREMENTS
Easy implementation on any AVANCE spectrometer.
VERSIONS
The basic pulse sequence is based in an heteronuclear antiphase
coherence transfer by means of simultaneous 1H and 13C 90º pulses
(
78JACS320
).
Due to antiphase character of the detected signals, no broadband proton
decoupling can be applied during acquisition. In addition, enhancement
according to the gyromagnetic constant ratio is obtained as known in INEPT-type
experiments. In order to simplify such spectra, a 13C 180º pulse could
be inserted into the evolution period
(
77JMR471-28
).
An altenative phase cycling to the original
(
84JMR515-56
)
and a phase-sensitive version
(
88JMR125-77
)
of the FUCOUP experiment have been proposed. From the basic three-pulse
experiment, the classical and more suitable 2D HETCOR
experiment can be derived by introducing heteronuclear decoupling
in both dimensions. In addition, this same idea can be extended to heteronuclear
long-range correlation experiments.
EXPERIMENTAL DETAILS
The 2D FUCOUP experiment can be recorded in routine/automation
modes. The basic pulse sequence is free of fixed delays and therefore there
is no need to optimize any interpulse delay. Thus, only the standard parameters
as pulse widths, transmitter frequencies, levels of digitization and sweep
widths in both F1 and F2 dimensions must be selected.
All possible direct and long-range XH correlations are observed
in a FUCOUP spectrum. In addition, chemical shift, H-X and H-H J-coupling
informations are also retained in both dimensions, rendering complex 2D
maps with low signal-to-noise ratio. Cross-peaks show antiphase pattern
with respect to the active proton-carbon coupling constant and in-phase
pattern with respect to all passive proton-proton coupling constants.
