Solvent extraction of europium trifluoromethanesulfonate into nitrobenzene by using three electroneutral receptors

From extraction experiments and \( \gamma \)-activity measurements, the extraction constants corresponding to the general equilibrium Eu3+(aq) + 3 A−(aq) + L(nb) \( \Leftrightarrow \) EuL3+(nb) + 3A−(nb) taking place in the two-phase water–nitrobenzene system (\( {\text{A}}^{ - } = {\text{CF}}_{ 3} {\text{SO}}_{3}^{ - } \); L = electroneutral receptors denoted by 1, 2, and 3 – see Scheme 1; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the EuL3+ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the series of 3 < 2 < 1. Open image in new window Scheme 1 Structural formulas of N,N,N′,N′,N″,N″-hexacyclohexyl-4,4′,4″-propylidynetris(3-oxabutyramide) (1), bis[(12-crown-4)methyl] dodecylmethylmalonate (2), and bis[(benzo-15-crown-5)-4′-ylmethyl] pimelate (3)