Recoupling of heteronuclear dipolar interactions in solid-state NMR using symmetry-based pulse sequences

We apply symmetry theorems to the problem of heteronuclear dipolar recoupli ng in the presence of magic-angle spinning in solid-state NMR. Examples are shown in which the C-13 NMR signal is acquired while rotor-synchronized pu lse sequences with the symmetry R18(1)(7) or R18(2)(5) are applied to the H -1 spins. This allows recoupling of heteronuclear dipolar interactions comb ined with homonuclear decoupling of the irradiated H-1 spins. The structure of the C-13 NMR spectrum is sensitive to bond lengths and bond angles. A t wo-dimensional procedure is described for applications to multiply isotopic ally labelled systems. (C) 2001 Elsevier Science B.V. All rights reserved.