Electrolytic preparation, redox titration and stability of pentavalent state of uranyl tetraketonate in dimethyl sulfoxide

Uranyl(VI) complex with tetraketone ligand, m-bis(2,4-dioxo-l-pentyl)benzene, which possesses two monomer acetylacetone moieties was synthesized. Cyclic voltammetric study on U(VI)/U(V) couple revealed that this electrode reaction is simple reversible reaction on glassy carbon (GC) electrode in dimethyl sulfoxide (DMSO). Electrolytic preparation of DMSO solution of uranyl(V) tetraketonate was carried out starting from the corresponding uranyl(VI) complex by using a flow electrolysis system. New redox titration method using bis(cyclopentadienyl)iron(III) hexafluorophosphate (FcPF₆) was developed and used for quantitative analysis of uranyl(V). Titration curve of uranyl(V) tetraketonate was explained by a simple oxidation by FcPF₆, in contrast to the result of uranyl(V) acetylacetonate. Half-life of the uranyl(V) tetraketonate was determined by spectrophotometry as 3.7 h, which is much longer than 1.5 h of uranyl(V) acetylacetonate.