Probing the oxygen environment in UO22+ by solid-state O17 nuclear magnetic resonance spectroscopy and relativistic density functional calculations

A combined theoretical and solid-state O17 nuclear magnetic resonance (NMR) study of the electronic structure of the uranyl ion UO22+ in (NH4)4UO2(CO3)3 and rutherfordine (UO2CO3) is presented, the former representing a system with a hydrogen-bonding environment around the uranyl oxygens and the latter exemplifying a uranyl environment without hydrogens. Relativistic density functional calculations reveal unique features of the U–O covalent bond, including the finding of O17 chemical shift anisotropies that are among the largest for oxygen ever reported (>1200 ppm). Computational results for the oxygen electric field gradient tensor are found to be consistently larger in magnitude than experimental solid-state O17 NMR measurements in a 7.05 T magnetic field indicate. A modified version of the Solomon theory of the two-spin echo amplitude for a spin-5/2 nucleus is developed and applied to the analysis of the O17 echo signal of U O1722+.