The Complexation of Lanthanides by Glycolamide Extractants: Evidences from Electronic Spectroscopy and DFT Calculations

The extraction of trivalent metal ions (Nd and Eu) in N,N,N',N'-tetraoctyldiglycolamide (TODGA) was compared with N,N-di-octyl-2-hydroxyacetamide (DOHyA), a monoglycolamide derivative of TODGA. The studies based on UV-visible spectroscopy showed the differences in Nd(III) ion complexation for the extractants in both polar and non-polar diluents. n-Dodecane modified with 5 vol% 1-octanol was employed as diluent for extraction studies with TODGA, while DOHyA was studied with no modifiers in n-Dodecane. Time resolved luminescence spec-troscopy studies of the Eu(III) extracted organic phases showed strong complexation of metal ion with both the extractants. The co-extraction of water in DOHyA solvent phase during Eu(III) extraction from nitric acid me-dium was found to be more as compared to TODGA. The better solubilization of water in DOHyA solvent was substantiated by DFT analysis of the optimized electronic structures of Eu-DMHyA (dimethyl hydroxyacetamide) and Eu-TMDGA (tetramethyldiglycolamide) complexes.