Heteronuclear local field NMR spectroscopy under fast magic-angle sample spinning conditions

The acquisition of bidimensional heteronuclear nuclear magnetic resonance l ocal field spectra under moderately fast magic-angle spinning (MAS) conditi ons is discussed. It is shown both experimentally and with the aid of numer ical simulations on multispin systems that when sufficiently fast MAS rates are employed, quantitative dipolar sideband patterns from directly bonded spin pairs can be acquired in the absence of H-1-H-1 multiple-pulse homonuc lear decoupling even for "real" organic solids. The MAS speeds involved are web within the range of commercially available systems (10-14 kHz) and pro vide sidebands with sufficient intensity to enable a reliable quantificatio n of heteronuclear dipolar couplings from methine groups. Simulations and e xperiments show that useful information can be extracted in this manner eve n from more tightly coupled -CH2- moieties, although the agreement with the patterns simulated solely on the basis of heteronuclear interactions is no t in this case as satisfactory as for methines, Preliminary applications of this simple approach to the analysis of molecular motions in solids are pr esented; characteristics and potential extensions of the method are also di scussed. (C) 2000 Academic Press.