Extraction and complexation studies of N-methyl-N-phenyl-2-(1H-benzimidazol-2-yl)pyridine-6-carboxamide with trivalent lanthanide

Akutsu, Kazuhiro*; Suzuki, Shinichi; Kobayashi, Toru ; Shiwaku, Hideaki   ; Okamoto, Yoshihiro  ; Yaita, Tsuyoshi

The extractability and complexation properties of trivalent lanthanides with N-methyl-N-phenyl-2-(1H-benzimidazol-2-yl)pyridine-6-carboxamide (MePhBIZA) were investigated. The MePhBIZA, containing two aza-aromatic donors and an oxygen donor in the molecule, was designed with regard to 2-(2-pyridyl)benzimidazole (Biz) and newly synthesized as an extractant for trivalent lanthanides, Ln, and actinides, An. The MePhBIZA exhibited satisfactory extractability of Eu even under acidic conditions. A speciation diagram, based on the formation constants determined by spectroscopic titration experiments, indicated that the MePhBIZA formed complexes with Eu in acidic solution. These results showed that the addition of the amide group promotes ligand coordination with Eu over the competing protonation reaction in relatively acidic solution in comparison with Biz.