Characterization of the extracted complexes of trivalent lanthanides with purified cyanex 301 in comparison with trivalent actinide complexes

Abstract

The extracted complexes of trivalent lanthanides (Ln(III)) with purified Cyanex 301 (bis(2,4,4-trimethylpentyl)dithiophosphinic acid, denoted as HA) were investigated by extended X-ray absorption fine structure spectroscopy (EXAFS), UV-Vis and fluorescence spectroscopy. In the complexes prepared under the same conditions of solvent extraction, the light Ln(III) ions are mainly coordinated by the sulfur atoms of the ligands, and the middle Ln(III) ions are coordinated by mixed donors, the sulfur atoms of the ligands and the oxygen atoms of the extracted water, while the heavy Ln(III) ions are completely hydrated in the organic phase without any sulfur atoms of the ligands in the coordination shell. As the atomic number increases, the extracted water molecules gradually replace the sulfur atoms of the ligands in the first coordination shell of Ln(III), and simultaneously the ligand anions become counterions just for balancing the positive charge of the fully hydrated heavy Ln(III) ions. The effect of the change in the complex structures on the extraction of Ln(III) ions with HA was evaluated by the co-extraction of other thirteen individual Ln(III) together with Nd(III). In contrast to most ligands bonding more strongly to heavier Ln(III), HA preferentially extracts lighter Ln(III), suggesting that the unusual extraction capability of HA for Ln(III) might originate from the difference in the complex structures with Ln(III) ions.

Quantum Chemistry Study on the Extraction of Trivalent Lanthanide Series by Cyanex301: Insights from Formation of Inner- and Outer-Sphere Complexes

“…This was not investigated in our calculation, but one can infer from Figure 8 a formation of transition-mode complex for Eu(III). This is in line with our previous observations in both extraction system and homogeneous solution with high metal loading, 14,18 but contrary to the results by using extended X-ray absorption fine structure with very low metal loading. 10 Once again, this reflects the complexity of the extraction system using Cyanex301 as the extractant.…”

“…10 In the extraction of the lanthanides series by HC301, however, our group previously observed different extracted complexes for different lanthanides under the same extraction condition. 14 The light Ln(III) are mainly coordinated by the sulfur atoms of the ligands (inner-sphere complexes), and the middle Ln(III) are coordinated by mixed donors, the sulfur atoms of the ligands and the oxygen atoms of the extracted water, whereas the heavy Ln(III) are completely hydrated in the organic phase without any sulfur atoms of the ligands in the coordination shell (outer-sphere complexes). Furthermore, even for light Ln(III), such as Nd(III), water molecules are able to replace C301 anions in the first coordination shell to coordinate with the metal ions at high neutralization degree, forming outer-sphere complexes and even more complicated supramolecular aggregations in organic phase, i.e., water-in-oil (W/O) microemulsions.…”

“…In 1995, Zhu et al found that purified Cyanex301, i.e., bis­(2,4,4-trimethylpentyl)­dithiophosphinic acid (denoted as HC301, Figure ), which is a S-donor ligand, could selectively extract Am­(III) from Ln­(III) with an extremely high separation factor over 1000 . Since then, a number of experiments have been carried out to investigate the extraction behaviors and, especially, to identify of the extracted complexes of both An­(III) and Ln­(III) in organic phase. − It was demonstrated by Jensen et al that the structure and metal–donor atom bond distances are indistinguishable within experimental error for similarly sized trivalent lanthanide and actinide cations, despite the extraordinary selectivity of HC301 for trivalent actinide cations over trivalent lanthanide cations . In the extraction of the lanthanides series by HC301, however, our group previously observed different extracted complexes for different lanthanides under the same extraction condition .…”

“…Since then, a number of experiments have been carried out to investigate the extraction behaviors and, especially, to identify of the extracted complexes of both An­(III) and Ln­(III) in organic phase. − It was demonstrated by Jensen et al that the structure and metal–donor atom bond distances are indistinguishable within experimental error for similarly sized trivalent lanthanide and actinide cations, despite the extraordinary selectivity of HC301 for trivalent actinide cations over trivalent lanthanide cations . In the extraction of the lanthanides series by HC301, however, our group previously observed different extracted complexes for different lanthanides under the same extraction condition . The light Ln­(III) are mainly coordinated by the sulfur atoms of the ligands (inner-sphere complexes), and the middle Ln­(III) are coordinated by mixed donors, the sulfur atoms of the ligands and the oxygen atoms of the extracted water, whereas the heavy Ln­(III) are completely hydrated in the organic phase without any sulfur atoms of the ligands in the coordination shell (outer-sphere complexes).…”

Syntheses and characterization of new dithiophosphinato zinc complexes

“…Acidic organodithiophosphorus compounds like dithiophosphoric, dithiophosphonic and dithiophosphinic acids ( Figure 1) and the coordination compounds thereof have some industrial interest because of their use as a rubber vulcanizing agent (1,2), lubricating oil additives (3)(4)(5), metal flotation mediators (6)(7)(8), and pesticides (9)(10)(11). Potential uses as chemotherapeutic agents (12), clinical imaging aids (13) and antibiotic synergists are also investigated (14).…”