Magic-angle spinning phosphorus-31 nuclear magnetic resonance of polycrystalline sodium phosphates

Abstract

The magic-angle spinning ³¹P n.m.r. spectra of a range of solid sodium ortho-, pyro-, poly-, and metaphosphates have been obtained. Counter ion, hydration state, crystalline form and inequivalence within a molecule all affect the solid-state chemical shift, which therefore deviates from the solution chemical shift. The multiplicity of ³¹P resonances indicates a level of structural inequivalence at least as large as that revealed by X-ray diffraction. Shielding anisotropies have also been obtained, which agree with previous studies but additionally show deviation from isotropic symmetry for some orthophosphates and deviation from axial symmetry for some terminal polyphosphate groups.