Unprecedented Inversion of Selectivity and Extraordinary Difference in the Complexation of Trivalent f Elements by Diastereomers of a Methylated Diglycolamide

Abstract

When considering f elements, solvent extraction is primarily used for the removalo fl anthanides from orea nd their recycling, as well as for the separationo fa ctinides from used nuclear fuel. Understanding the complexation mechanism of metal ions with organic extractants, particularly the influence of their molecular structure on complex formation is of fundamentali mportance.H erein, we report an extraordinary (up to two orders of magnitude)c hange in the extraction efficiency of f elements with two diastereomers of dimethyl tetraoctyld iglycolamide (Me 2 -TODGA), which only differ in the orientation of as inglem ethyl group. Solvente xtraction techniques, extended X-ray absorption fine structure (EXAFS)m easurements,a nd density functional theory( DFT) based ab initio calculations were used to understandt heir complex structures and to explain their complexation mechanism.W es how that the huge differences observed in extraction selectivity results from as mall changei nt he complexation of nitrate counter-ions caused by the different orientation of one methylg roup in the backboneo ft he extractant.T he obtained results give as ignificant new insight into metal-ligandc omplexation mechanisms,w hichw ill promote the development of more efficient separation techniques.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Efficient Separation of Light Lanthanides(III) by Using Bis‐Lactam Phenanthroline Ligands

“…Only ah andful of neutral ligandst hat exhibit high selectivity for light lanthanides in solvent extraction systems have been previously described. [5][6][7][8] Them ajorityo ft he known ligandse xhibit the reverse trend, that is, by being more selectivet owardsh eavy lanthanides.E xamples include acidic compounds, such as bis(2-ethylhexyl) phosphoric acid (D2EHPA), [9] am ixture of phosphinica nd phosphonic acids (Cyanex572) [10] and bis(2ethylhexyl)phosphinic acid, [11] and neutral compounds, [12] such as N,N,N',N'-tetraoctyldiglycolamide (TODGA), [13][14][15] trialkylphosphine oxides( e.g.,C yanex9 23) [16] and bis-triazinylpyridine, [17][18][19] to mention but afew.…”

“…The majority of the known ligands exhibit the reverse trend, that is, by being more selective towards heavy lanthanides. Examples include acidic compounds, such as bis(2‐ethylhexyl) phosphoric acid (D2EHPA), a mixture of phosphinic and phosphonic acids (Cyanex 572) and bis(2‐ethylhexyl)phosphinic acid, and neutral compounds, such as N , N , N ′, N ′‐tetraoctyldiglycolamide (TODGA), trialkylphosphine oxides (e.g., Cyanex 923) and bis‐triazinylpyridine, to mention but a few.…”

Pyrochlore Compounds From Atomistic Simulations

“…This is not expected as Cm 4+ has smaller ionic radius than Am 4+ . We note, however, that such a subtle differences have been observed due to so-called tetrad effect associated with the number of electrons in f shells (e.g., Wilden et al (2019) ). On the computational side, the reason for this is a significantly larger Hubbard U parameter value derived for Cm 4+ than that for Am 4+ or Cm 3+ ( Table 2 ).…”

Effect of diluent on the extraction of europium(iii) and americium(iii) with N,N,N′,N′-tetraoctyl diglycolamide (TODGA)

“…21 In order to further investigate the effects of diluent on extraction, the aim of this study is the systematic evaluation of the molecular diluent effect on the extraction of trivalent europium and americium from nitric acid solutions with N,N,N 0 ,N 0 -tetraoctyl diglycolamide as an extracting agent. The family of diglycolamides are known extracting agents for trivalent lanthanides and actinides in solvent extraction, with expected application in partitioning and transmutation of a nuclear fuel [22][23][24][25] and in radiopharmaceutical industry for 225 Ac production. [26][27][28][29] While the behavior of diglycolamides with respect to equilibrium distribution ratios, acid extraction and kinetics was extensively evaluated, [30][31][32][33][34][35][36][37][38][39][40][41][42] the effect of the diluent on the extraction was evaluated only in a few studies.…”