Extraction Ability of 4-Benzoyl-3-phenyl-5-isoxazolone towards 4f-Ions into Ionic and Molecular Media

The distribution constants of 4-benzoyl-3-phenyl-5-isoxazolone (HPBI) and deprotonated one (PBI^-) between hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C₁C₄im][Tf₂N]) and aqueous phases were determined, together with the acid-dissociation constant of HPBI. The solvent extraction of three selected lanthanoid ions (La³⁺, Eu³⁺, and Lu³⁺) with HPBI from aqueous nitrate phase into [C₁C₄im][Tf₂N] has been investigated. Application of the ionic liquid as the extracting phase greatly enhanced the extraction performance of HPBI for lanthanoid ions compared with that in the chloroform system. A slope analysis was conducted in order to compare the results of the solution 4f-ion coordination chemistry in ionic and molecular media. The composition of the extracted species was established to be anionic tetrakis entities, Ln(PBI)₄^-, for light, middle, and heavy lanthanoid ions in an ionic environment (Ln denotes lanthanoid ion). Nevertheless, the typical neutral chelate lanthanoid complexes of the type Ln(PBI)₃ have been detected when the conventional molecular diluent chloroform was applied as an organic phase.