Complexation and extraction studies of lanthanide ions by 1,1′-(3,6,9-Trioxaundecanedionyl)Diphenothiazine

Solid complexes of lanthanide picrates with 1,1′-(3,6,9-trioxaundecanedionyl)diphenothiazine (L), [Ln(pic)₃L] (Ln = La, Nd, Eu, Gd, Er, Y), have been prepared and characterized by elemental analysis, IR and ¹H NMR spectra. The molecular structure of [Er(pic)₃L]·1/2C₂H₅OH shows that five oxygens of L form a ring-like coordination structure. Er(III) is 9-coordinated by L together with the other two unidentate and one bidentate picrate anions, revealing a tri-capped distorted trigonal prism geometry. Solvent extraction of Ln(III) with L has been carried out in a water-nitrobenzene system by use of the multitracer method. The relationship between the complex structure and extractabilities of the ligand is discussed.