Triple-quantum NMR spectroscopy in dipolar solids

Triple-quantum (TQ) NMR spectroscopy in dipolar solids under fast magic-angle spinning is introduced. Proton dipolar connectivities derived from two-dimensional high-resolution TQ NMR spectra are shown for bisphenol-A-polycarbonate, fully protonated and OH-deuterated dimethylglyoxime and acetonitrile trapped in the cages of perdeuterated hydroquinone. For spin-1/2-triads, fast rotating about their threefold symmetry axis, MAS-induced TQ spinning-sideband patterns are evaluated. Analytical treatment of isolated spin-1/2-triads is compared to numerical spin-dynamics simulations including influences of surrounding spins with respect to effects on both the integral intensities of TQ coherences and the signal distribution on TQ sideband patterns. Using the above samples, which contain methyl groups in different surroundings, the perturbing effects of neighboring protons are elucidated.