³¹P MAS-NMR Study of Some Alkali Rare-Earth Cyclo- and Polyphosphates

Abstract

Several alkali rare-earth polyphosphates have been analyzed by high-resolution 31P MAS-NMR (magic angle spinning nuclear magnetic resonance) spectroscopy. From their NMR spectra, the number and the multiplicity of crystallographic sites have been analyzed in the NH4LaP4O12 cyclophosphate and in MI2La(PO3)5 (M = NH4, K) and MILnIII(PO3)4 (M = Li, Na, Ag, K, Rb, Cs, Tl; Ln = La, Sm), long-chain polyphosphates. A linear dependence of NMR isotropic chemical shift values on the mean POP angles of the chain, calculated from data published on isostructural compounds, has been deduced. Chemical shift anisotropies of NMR components have been analyzed in terms of the structural characteristics of the environment of P atoms.