SPECTROSCOPY AND ELECTROCHEMISTRY OF U(IV)/U(III) IN BASIC ALUMINUM CHLORIDE-1-ETHYL-3-METHYLIMIDAZOLIUM CHLORIDE

The redox chemistry of UCl4 has been investigated in the solvent AlCl3-1-ethyl-3-methylimidazolium chloride (AlCl3-EMIC), a room-temperature ionic liquid. In basic solutions (< 50 mol % AlCl3) the reduction of U(IV) to U(III) on glassy carbon electrodes is reversible. Visible/near-IR spectroscopic data and potentiometric measurements for U(IV)/U(III) as a function of the basic composition of AlCl3-EMIC indicate U(IV) and U(III) are both hexachloro anions. Diffusion coefficients were measured for the U(IV) and U(III) complexes by two methods. The values are comparable to those of transition-metal hexachloro anionic complexes in the same solvent, supporting the assignment of [UCl6]2- and [UCl6]3-.