Symmetry-based recoupling of proton chemical shift anisotropies in ultrahigh-field solid-state NMR

A two-dimensional NMR experiment for estimating proton chemical shift anisotropies (CSAs) in solid powders under magic-angle spinning conditions is demonstrated in which H-1 CSAs are reintroduced with a symmetry-based recoupling sequence while the individual proton sites are resolved according to their isotropic chemical shifts by magic-angle spinning (MAS) or combined rotation and multiple pulse (CRAMPS) homonuclear decoupling. The experiments where carried out on an ultrahigh-field solid-state NMR instrument (900 MHz H-1 frequency) which leads to increased resolution and reliability of the measured H-1 CSAs. The experiment is expected to be important for investigating hydrogen bonding in solids. Crown Copyright (c) 2006 Published by Elsevier Inc. All rights reserved.