Structural study of phosphate groups in layered metal phosphates by high-resolution solid-state P-31 NMR spectroscopy

In studies of a series of crystals of layered metal phosphate compounds by magic angle spinning (MAS) NMR spectroscopy, it has been found that there is a distinct correlation between the P-31 isotropic chemical shift value and the type of phosphate group. The isotropic P-31 chemical shifts of (H2PO4)(-), (HPO4)(2-) and (Pb-4)(3-) groups appear around delta - 10, - 20 and - 30, respectively. These assignments were made unambiguously by measuring the P-31 MAS NMR spectra with and without H-1 high-power decoupling together with the cross-polarization transfer technique between H-1 and P-31 nuclei (CP MAS spectra).