The complexation of lanthanides by glycolamide extractants: Evidences from electronic spectroscopy and DFT calculations

Abstract

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 spectroscopy 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 medium 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.