Separation of americium(III) from europium(III) with tridentate heterocyclic nitrogen ligands and crystallographic studies of complexes formed by 2,2′∶6′,2″-terpyridine with the lanthanides

Abstract

Phenyl-substituted derivatives of 2,2Ј : 6Ј,2Љ-terpyridine and a corresponding bipyridine-pyrazine derivative have been shown to have metal extraction properties and separation factors for americium() over europium() which are comparable to those previously obtained for 2,2Ј : 6Ј,2Љ-terpyridine (L 1 ). The extracting agents in either tertbutylbenzene (TBB) or hydrogenated tetrapropene (TPH) gave D Am /D Eu separation factors (SFs) between 7 and 9 when used to extract the metal ions from 0.01-0.1 M nitric acid solution in synergistic combination with 2-bromodecanoic acid. In contrast to L 1 , the new hydrophobic ligands have little or no solubility in the aqueous phase. In an effort to better understand the nature of the species which may be involved in the extraction process, a series of metal-L 1 complexes which cover the lanthanides have been prepared. Five different structural types have been established for the lanthanide coordination complexes. In type 1,, the metal is 10-coordinate being bonded to one terdentate L 1 ligand, three bidentate nitrates and a water molecule. In type 2,Tb, Dy and Ho), the metal atom in the cation is 10-coordinate, being bonded to two terdentate L 1 ligands and two bidentate nitrates; in the anion the metal is also 10-coordinate, being bonded to one terdentate L 1 ligand and four nitrates, of which three are bidentate and one unidentate. In type 3, [M(NO 3 ) 3 (L 1 )(H 2 O)]ؒL 1 (M = Ho, Er, Tm and Yb), the metal is 10-coordinate, being bonded to three bidentate nitrates, one terdentate L 1 and a water molecule. In addition, an L 1 ligand is found in the asymmetric unit which is hydrogen-bonded to the coordinated water molecule. In type 4, [M(NO 3 ) 3 (L 1 )(H 2 O)] (M = Tm), the metal is 9-coordinate, being bonded to two bidentate nitrates, one unidentate nitrate, one terdentate L 1 ligand and a water molecule. In type 5, [M(NO 3 ) 3 (L 1 )] (M = Yb), the metal is 9-coordinate, being bonded to three bidentate nitrates and one terdentate L 1 ligand. A sixth structural type was observed for M = La in the crystal structureThe metal is not bound to L 1 but instead forms the well-known hexanitrate anion. This complex may give some indication of the type of species which could be formed at higher acid concentrations in the aqueous phase, where protonation of L 1 can occur.

A Versatile Six-Component Molecular Capsule Based on Benign Synthons − Selective Confinement of a Heterogeneous Molecular Aggregate

“…The terpyridine was conveniently prepared in high yield involving sequential solvent-free aldol and Michael addition reactions, as recently developed for related terpyridines, [30] for which conventional methods are low yielding and generate considerable waste. [31,32] The calix [4]resorcinarene was also readily prepared in high yield as the cavitand C 4v isomer under solvent-free conditions, [33] which dispenses with the need for using large volumes of acid and solvent. [34] The solid state structures of 1 and 2 were determined by X-ray crystallography.…”

Calixarene‐Based Picolinamide Extractants for Selective An/Ln Separation from Radioactive Waste

“…[9] However, An/Ln separation can be more easily achieved by exploiting the slightly stronger interactions that An III present with the softer S-and N-containing ligands [1,3] of the SANEX processes. [10,11] Different pyridine derivatives, such as terpyridines and 2,6-bis(triazinyl)pyridines, [12][13][14][15][16] or dithiophosphinic acids [17][18][19] show quite remarkable separation factors. Among these ligands, N-alkylpicolinamides have also been proposed as ligands for the selective extraction of An from radioactive waste [2,20,21] as they show promising separation factors (S Am/Eu Ϸ 9) under optimum conditions.…”

QSAR studies of multidentate nitrogen ligands used in lanthanide and actinide extraction processes

“…The crystal structures show that a wide variety of complexes can be formed. We have demonstrated that the majority of complexes with L 1 [5,6], L 2 [7,8], and L 3 [9,10] contain metal ligand ratios of 1:1. The most common stoichiometry of these complexes is [LaL(NO 3 ) 3 ] as shown in Fig.…”