Anomalous lanthanoid(III) species extracted with 4-isopropyltropolone and neutral ligands in an ionic liquid

The solvent extraction behavior of trivalent lanthanide ions (Ln(III)), such as La(III), Eu(III), and Lu(III) with 4-isopropyltropolone (Hipt) and trioctyphosphine oxide (topo) in an ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bmim][Tf2N]) was studied. Based on the 3-dimensional equilibrium analysis, the extracted species of Ln(III) into IL phase with Hipt alone were found to be the cationic self-adduct complex such as Ln(ipt)2(Hipt)+ or Ln(ipt)2(Hipt) 2 + as well as neutral chelate complex such as Ln(ipt)3 which are totally different from binuclear complexes that are extracted in chloroform and toluene. In the presence of topo, the extractability of Ln(III) was enhanced significantly, and two kinds of cationic complexes such as Ln(ipt)2(topo)+ and Ln(ipt)(topo) 3 2+ are found to be extracted, indicating that the neutral ligand accelerates the extraction of the highly charged species into IL phase. Compared with the extraction behavior with benzoylacetone, Hipt shows superior extractability of Ln(III) alone while the synergistic effect in the coexistence of topo is weak.