- K. Saalwächter.
Robust NMR Approaches for the Determination of
Homonuclear Dipole–Dipole Coupling Constants in Studies
of Solid Materials and Biomolecules.
Chem. Phys. Chem. 14, 3000-3014(2013).
This review addresses the NMR spectroscopy study of molecular
structure and dynamics by way of homonuclear dipole–
dipole couplings by relying on their orientation and direct distance
dependence. The study of homonuclear couplings as opposed
to heteronuclear couplings poses specific challenges.
On the one hand, two like spins cannot be independently manipulated
easily, which means that simple shift-refocusing concepts
by using hard p pulses cannot be used to cope with potentially
large chemical-shift dispersions at the high fields used
today. On the other hand, the noncommutativity of the different
pair Hamiltonians in a multispin system leads to complications
associated with the isolation of specific pair couplings
while minimizing the influence of the other spins. In particular,
the so-called dipolar-truncation effect challenges the observation
of weak couplings of interest in the presence of stronger
ones. Recent advances in determining homonuclear dipole–
dipole coupling constants are reviewed, stressing the use of
double-quantum spectroscopy approaches and their similarity
to the popular heteronuclear rotational-echo double-resonance
experiment. Particular emphasis is put on corrections for the
influence of transverse relaxation effects on the measured
data, and the handling of distribution effects as well as potential
dynamic heterogeneities in complex substances.