Extraction of europium trifluoromethanesulfonate into nitrobenzene in the presence of some electroneutral calixarene ligands

From extraction experiments and gamma-activity measurements, the extraction constants corresponding to the general equilibrium Eu3+(aq) + 3 A(-)(nb) + L(nb) < -> EuL3+(nb) + A(-)(nb) taking place in the two-phase water-nitrobenzene system (A(-) -CF3SO3-; L = tetrakis(2-ethoxyethoxy)- tetra-p-tert-butylcalix[4] arene (1), tetraethyl p-tert-butylcalix[ 4] arene tetraacetate (2), p-tert-butylcalix[4] arene-tetrakis(N, N-diethylacetamide) (3), hexaethyl p-tert-butylcalix[ 6] arene hexaacetate (4), p-tert-butylcalix [6] arene-hexakis(N, N-diethylacetamide) (5); 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 2 < 4 < 1 < 5 < 3.