Understanding the separation of trivalent lanthanides and actinides using multiple diglycolamide-containing ligands: a review

The complexation and separation behaviour of trivalent actinides and lanthanides with various multiple diglycolamide (DGA) group-containing ligands are compiled in the present review. The DGA arms are anchored on various scaffolds, viz., C- and N-pivot tripodal backbones, benzene-centred tripodal backbones, calix[4]arene, pillar[5]arene and azamacrocycle scaffolds. Dendrimers of different generations having DGA arms were also evaluated for the extraction and complexation studies of trivalent actinide and lanthanide ions. The extraction efficiency of the DGA units increases significantly when they are grouped together on a single backbone/scaffold. Furthermore, the selectivity was found to improve in many cases, particularly with respect to the UO₂²⁺ ion. This is very important for the development of suitable ligands for the extraction/separation of the actinide and lanthanide ions. Combined experimental, luminescence and DFT studies on the complexation of trivalent actinides and lanthanides with these DGA-based ligands are quite useful to understand their extraction and separation behaviour and this review article gives a critical analysis of the results available in the literature.