TRIPLE-QUANTUM NMR-SPECTROSCOPY IN DIPOLAR SOLIDS

Triple-quantum (TQ) NMR spectroscopy in dipolar solids under fast magi c-angle spinning is introduced. Proton dipolar connectivities derived from two-dimensional high-resolution TQ NMR spectra are shown for bisp henol-A-polycarbonate, fully protonated and OH-deuterated dimethylglyo xime and acetonitrile trapped in the cages of perdeuterated hydroquino ne. For spin-1/2-triads, fast rotating about their threefold symmetry axis, MAS-induced TQ spinning-sideband patterns are evaluated. Analyti cal treatment of isolated spin-1/2-triads is compared to numerical spi n-dynamics simulations including influences of surrounding spins with respect to effects on both the integral intensities of TQ coherences a nd the signal distribution on TQ sideband patterns. Using the above sa mples, which contain methyl groups in different surroundings, the pert urbing effects of neighboring protons are elucidated. (C) 1998 Publish ed by Elsevier Science B.V.