Paramagnetic shift probes in high-resolution solid-state NMR

Abstract

Small additive shifts due to changes in the local environment of the resonating nucleus have been observed in magic-angle spinning nuclear magnetic resonance (MASNMR) studies of several classes of solid. The ²⁹.Si resonances in zeolites, for example, shift by approximately 5 p.p.m. per aluminium next-nearest-neighbour^1,2, and similar effects have been observed in ³¹P MASNMR spectra of Zn_3−xMg_x (PO₄)₂ solid solutions³. The use of paramagnetic ions to induce large chemical shifts is well established in solution NMR⁴ and has also been observed for molecular structures in the solid state⁵. Here we describe a ¹¹⁹Sn study of the pyrochlore solid solution, Y_2−xSm_x,Sn₂O₇, and show for the first time the use of paramagnetic shifts in MASNMR to probe the structures of continuous solids.