Spectral editing in C-13 MAS NMR under moderately fast spinning conditions

Novel procedures for the spectral assignment of peaks in high-resolution so lid-state C-13 NMR are discussed and demonstrated. These methods are based on the observation that at moderate and already widely available rates of m agic-angle spinning (10-14 kHz MAS), CH and CH, moieties behave to a large extent as if they were effectively isolated from the surrounding proton res ervoir. Dipolar-based analogs of editing techniques that are commonly used in liquid-state NMR such as APT and INEPT can then be derived, while avoidi ng the need for periods of homonuclear H-1-H-1 multipulse decoupling, The r esulting experiments end up being very simple, essentially tuning-free, and capable of establishing unambiguous distinctions among CH, CH2, and -C-/-C H3 carbon sires. The principles underlying such sequences were explored usi ng both numerical calculations and experimental measurements, and once vali dated their editing applications were illustrated on a number of compounds. (C) 2001 Academic Press.