Extractive complexation of lanthanides and Am(III) by 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone in ionic liquid: Solvent extraction and spectroscopic studies

Extraction behaviour of trivalent actinides and lanthanides was studied using solutions of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP), a beta-diketone, in a room temperature ionic liquid, 1-methyl-3-octyl-imidazolium bis(trifluoromethylsulphonyl) imide (C 8 mim·Tf 2 N). The complex extracted into C 8 mim·Tf 2 N differs in its composition than those observed in molecular diluents such as benzene. Whereas, neutral ML 3 complex is predominant in molecular diluents, a positively charged complex, [ML 2 ·HL] + (where M = La 3 + , Eu 3 + , Lu 3 + and Am 3 + ; L = PMBP − ; HL = HPMBP), was identified to be extracted into the ionic liquid medium. Luminescence spectroscopic studies suggested presence of four inner-sphere water molecules in the extracted species. This paper reports for the first time the stability constant of a lanthanide (Nd 3 + ) complex with HPMBP in C 8 mim·Tf 2 N which are significantly larger than those reported in molecular diluents. Thermodynamic parameters were also determined to throw light on the nature of complexation.