A comparative study on the coordination of diglycolamide isomers with Nd(iii): extraction, third phase formation, structure, and computational studies

Abstract

A novel asymmetric diglycolamideN,N-dimethyl-N′,N′-dioctyl diglycolamide (LII) was synthesized. The Nd(iii) extraction behavior from HNO3and loading capability of the solution of LIIin 40/60 (v/v)%n-octanol/kerosene were studied. Analyses by the slope method, ESI-MS, and FT-IR indicated that, similar to the previously studied isomer ligandN,N′-dimethyl-N,N′-dioctyl diglycolamide (LI), 1 : 3 Nd(iii)/LIIcomplexes formed. Under the same experimental conditions, the distribution ratio and limiting organic concentration of LIItowards Nd(iii) were smaller than those of LI, but the critical aqueous concentration of LIIwas larger, which implies that LIIexhibited poorer extraction and loading capabilities towards Nd(iii) than LI, and LIIhas a tendency to be less likely to form the third phase. The quasi-relativistic density functional theory (DFT) calculation was performed to provide some explanations for the differences in their extraction behaviors. The electrostatic potential of the ligands indicated that the electron-donating ability of the amide O atoms in LIIdisplayed certain differences compared with LI. This inhomogeneity in LIIaffected the interaction between LIIand Nd(iii), as supported by QTAIM and bonding nature analysis, and it seemed to reflect in the extraction performance towards Nd(iii).