Probing Ni[S₂PR₂]₂ Electronic Structure to Generate Insight Relevant to Minor Actinide Extraction Chemistry

Abstract

A method to evaluate the electronic structure of minor actinide extractants is described. A series of compounds containing effective and ineffective actinide extractants (dithiophosphinates, S(2)PR(2)(-)) bound to a common transition metal ion (Ni(2+)) was analyzed by structural, spectroscopic, and theoretical methods. By using a single transition metal that provides structurally similar compounds, the metal contributions to bonding are essentially held constant so that subtle electronic variations associated with the extracting ligand can be probed using UV-vis spectroscopy. By comparison, it is difficult to obtain similar information using analogous techniques with minor actinide and lanthanide complexes. Here, we demonstrate that this approach, supplemented with ground state and time-dependent density functional theory, provides insight for understanding why high separation factors are reported for the extractant HS(2)P(o-CF(3)C(6)H(4))(2), while lower values are reported and anticipated for other HS(2)PR(2) derivatives (R = C(6)H(5), p-CF(3)C(6)H(4), m-CF(3)C(6)H(4)). The implications of these results for correlating electronic structure with the selectivity of HS(2)PR(2) extractants are discussed.

“Sweeping” Ortho Substituents Drive Desolvation and Overwhelm Electronic Effects in Nd3+ Chelation: A Case of Three Aryldithiophosphinates

“…The average Nd–S bond lengths are shown in Table S2. In the bare NdL 3 complex, the change of the average Nd–S distance is almost negligible by the introduction of a o -CF 3 group, which is in accordance with the crystal structure data of Ni–S bonds in Ni­[S 2 PR 2 ] complexes …”

Sulfur K-edge X-ray absorption spectroscopy and time-dependent density functional theory of arsenic dithiocarbamates

“…The S and As K-edge XAS were simulated using TDDFT as previously described. 29,[46][47][48][49] These calculations involve evaluating core electron excitations by exploiting the mixing between the valence orbitals on S and As. Specifically, this analysis involved a linear response calculation to extract the probability amplitudes from the transition densities and dipole moments between the calculated excited states and the ground states.…”

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

“…Density functional theory (DFT) calculation is a very powerful tool to predict and understand the coordination and extraction behavior of ligands in organic solvent toward metal ions in aqueous solution, especially in simulating the extraction separation process containing lanthanides and actinides, − although there are still some challenges due to the difficulties especially in treating relativistic effect and the f-electron correlation effects. Theoretical investigation on the extraction of Ln­(III) or An­(III) with Cyanex301 has been carried out by DFT calculations, to clarify the structure of the extracted complexes − and to correlate the extraction properties with the electronic structure variations of the ligands. − For example, Cao and co-workers carried out an excellent work of DFT calculation on the separation of An­(III) (An = Am and Cm) from Eu­(III) with Cyanex301 . The results showed that the neutral complexes M­(C301) 3 , where the C301 anion acts as a bidentate ligand and the metal ion is coordinated by six sulfur atoms, were likely the most stable extraction complexes, consistent with the experimental results reported by Jensen and co-workers .…”