Oxygen-17 NMR Study of the Uranyl Ion. II. Correlation between 17O NMR Chemical Shifts and Wavelengths of UV-Visible Absorption Bands of Uranyl Complexes

Abstract

17O NMR chemical shifts, UV-visible and IR spectra of a series of [UO2Ln](ClO4)2 (L=unidentate oxygen-donor ligand; n=coordination number) complexes in nonaqueous solvents have been measured. The electronic transition bands of the UO22+ entity shift toward lower energies with the increase in base strength of ligands in the equatorial plane. The asymmetric stretching frequencies of U=O bands are also affected by the base strength of equatorial ligands and correlated with the lowest electronic transition energies of uranyl complexes with the same geometry. The 17O chemical shifts are shown to be related to the lowest electronic transition energies of uranyl complexes. It appears that oxygen isotope shifts in 17O NMR spectra of the uranyl ion are predominantly attributed to the increase in the lowest electronic transition energies.