High-resolution solid state 13C NMR studies of ferrocene as a function of magic angle sample spinning frequency

Abstract

High-resolution solid state 13C NMR spectra of polycrystalline ferrocene have been recorded, at room temperature, under conditions of magic angle sample spinning and high power 1H decoupling. It is shown that, contrary to naive expectations, the linewidth of the isotropic peak in the spectrum increases as the magic angle sample spinning frequency is increased. It is demonstrated, via experiments with variable decoupler field strength and experiments on ferrocene- d 10, that this effect results from the efficiency of the 1H decoupling being modulated by magic angle sample spinning. The fact that narrower linewidths are obtained at low magic angle sample spinning frequency for this material has important implications in the wider context of establishing optimum conditions for recording high-resolution 13C NMR spectra of solids, particularly when there is appreciable molecular motion in the solid.