Empirical correlations between Pb-207 NMR chemical shifts and structure in solids

Using Pb-207 magic angle spinning and static NMR, we have resolved and assigned different lead sites in crystalline lead oxides and lead silicates to their isotropic chemical shifts. Chemical shift anisotropies were also obtained for lead sites from the intensities of spinning sidebands. Empirical correlations between Pb-207 isotropic chemical shifts and structural parameters are proposed, For ionic compounds, we show good correlations between chemical shift and coordination number or mean bond length. For more covalent compounds, the best empirical correlation has been obtained by using the degree of oxygen s-p hybridization and second neighbor electronegativity similar to that previously used to characterize Si-29 shifts in aluminosilicates. The Pb2+ chemical shift anisotropies increase with more positive chemical shifts. These correlations, established for simple crystalline compounds, should allow better characterization of lead environments in disordered materials of complex composition.