Structure and complexation studies on 2,2'-bipyridyl and trivalent lanthanides

Nakase, Masahiko*; Takeshita, Kenji*; Kobayashi, Toru ; Shiwaku, Hideaki   ; Yaita, Tsuyoshi

Separation of trivalent lanthanides (Ln) and trivalent actinides (An) is important task in reprocessing high-level liquid waste. In this study, the relationship between structures of complexes of 2,2'-bipyridyl (Bpy) and Ln and coordination strengths were investigated by X-ray diffraction and UV titration. With the decrease in ionic radius from Nd to Er, the N(Bpy)-Ln distance and N(Bpy)-Ln-N(Bpy) angle decreased, the dihedral angle of the Bpy pyridines increased, and the stability constant increased. This information about structure and coordination strength is important for designing better ligands for separating Ln and An ions.