Design and coordination behavior of the first selective recognition ligand of 147Pm(iii)

Abstract

A new amide tripodal ligand, 6-[2-(2-diethylamino-2-oxoethoxy)ethyl]-N,N,12-triethyl-11-oxo-3,9-dioxa-6,12-diazatetradecanamide (4) has been designed and synthesized for the recognition of rare earth ions. Three representative complexes of trivalent lighter (La), middle (Gd), and heavier (Er) rare earth ions with 4 were synthesized and characterized by X-ray crystallography. In the complex, the heptadentate 4 forms a cup-like coordination cavity encapsulating the central ion. Different supramolecular complex dimers are constructed by π–π interaction and van der Waals forces in accordance with the lanthanide contraction. The differences of the cavity and dimer structures were investigated further by assessing the separation efficiency of 4 in multitrace solvent extraction of rare earth ions from picrate acid solution and the ligand has the best separation factor for ¹⁴⁷Pm(III).