First Report on the Complexation of Actinides and Lanthanides Using 2,2′,2′′-(((1,4,7-Triazonane-1,4,7-triyl)tris(2-oxoethane-2,1-diyl)) tris(oxy)) tris(N,N-dioctylacetamide): Synthesis, Extraction, Luminescence, EXAFS, and DFT Studies

Abstract

A novel tripodal diglycolamide ligand containing a triazamacrocycle center (2,2′,2′′-(((1,4,7-triazonane-1,4,7-triyl)­tris­(2-oxoethane-2,1-diyl)) tris­(oxy)) tris­(N,N-dioctylacetamide), abbreviated as T9C3ODGA) was synthesized and characterized by conventional techniques. The ligand resulted in efficient extraction of actinide/lanthanide ions yielding the trend: Eu3+ > Pu4+ > Am3+ > NpO2 2+ > UO2 2+ > Sr2+ > Cs+. Similar to most of the other diglycolamide (DGA) ligands, Eu3+ was preferentially extracted as compared to Am3+; the separation factor (D Eu/D Am) value at 3 M HNO3 was ca. 4.2. In contrast, separation from UO2 2+ ion was less effective as compared to that of other tripodal DGA ligands studied earlier. Solvent extraction studies indicated extraction of species of the ML2 (where L is T9C3ODGA) stoichiometry. The formation of an inclusion complex with no inner-sphere water molecule was confirmed from luminescence spectral studies. DFT computations predicted the presence of an inner-sphere nitrate ion in the most preferred complex, which was also supplemented by EXAFS and luminescence studies. The selectivity of T9C3ODGA could be explained on the basis of its more favorable interactions with Eu3+ as compared to those with Am3+ both in the gas and the solution phases.

Evaluation of two aza-crown ether-based multiple diglycolamide-containing ligands for complexation with the tetravalent actinide ions Np4+ and Pu4+: extraction and DFT studies

“…The multiple DGA-containing ligand L I was prepared as reported. 23 L II was prepared following an analogous method, details of which are given in the ESI. † The purity of the ligands was checked by elemental analysis, NMR and HR-MS techniques.…”

“…This suggests that the extraction of Np 4+ ensures that of Pu 4+ as well. Knowing very well about the poor extraction of UO 2 2+ ion with multiple DGA-containing ligands, 18,[21][22][23] decontamination of the actinides can be easily achieved from U. The following sections include results of the other extraction studies.…”

“…1). 23 The promising results prompted us to explore the possibility of synthesizing a tetrapodal DGA ligand with a 'cyclen' (1,4,7,10tetrazacyclododecane) scaffold (L II ; Fig. 1).…”

Role of diluent in the unusual extraction of Am3+ and Eu3+ ions with benzene-centered tripodal diglycolamides: local structure studies using luminescence spectroscopy and XAS

“…2). 2,24 The addition of phase modifiers leads to a change in the physical/chemical parameters of the solvent, such as water or acid uptake, polarity etc., which can also influence the extraction of Ln 3+ /An 3+ with a given ligand. 33,34 For both ligands the acid and water uptake appeared to be very much similar (Table 1).…”

“…As the reverse micelle or 'self-assembly' formation requires the diluent to be non-polar, the whole phenomenon is controlled by the choice of diluent. This has been amply exploited by synthesizing DGA-functionalized calix [4]arenes, 23 or tripodals, 3,[24][25][26][27][28][29] which indeed gave very high extraction efficiencies for lanthanide and trivalent actinide ions. Amongst the tripodal ligands, benzene-centred tripodal diglycolamide (abbreviated as Benz-T-DGA) ligands have been found to be highly efficient for the extraction of the trivalent Ln 3+ /An 3+ ions.…”