Two-dimensional NMR correlations of liquid crystals using switched angle spinning

We present the first application of switched angle spinning (SAS) to correlate the first-order dipolar spectrum of a liquid crystalline sample with the isotropic magic angle spinning (MAS) spectrum in a two-dimensional experiment. In this experiment we are able to select the degree of dipolar couplings introduced via mechanical manipulations of the liquid crystal director in a single oriented sample. The F-19 SAS-COSY correlation of iodotrifluoroethylene, an AMX spin system, dissolved in the nematic liquid crystal 4-octylphenyl-2-chloro-4-(4-heptylbenzoyloxy)-benzoate provides assignment of both the J and dipolar couplings in a single experiment. This work demonstrates the use of oriented samples and sample spinning to resolve hornonuclear dipolar couplings using isotropic chemical shifts. (C) 2002 Elsevier Science (USA).