Complexation of trivalent lanthanides (Ln(III)) and actinides (An(III)) with a sulfur-bearing ligand, bis(2,4,4-trimethylpentyl) dithiophosphinate (C301), was studied by optical spectroscopy, microcalorimetry, luminescence lifetime measurement, and Extended X-ray Absorption Fine Structure (EXAFS). An(III) such as Cm(III) forms much stronger complexes with C301 than that of representative Ln(III) such as Nd(III). Moreover, in contrast to the general findings that heavier lanthanides form stronger complexes due to lanthanide contraction effect, the complexation strength between Ln(III) and C301 first increases from La(III) to Nd(III) and then decreases gradually toward heavier Ln(III) across the lanthanide series. The above trends agrees well with the results of solvent extraction using C301 as an extractant. The structural and thermodynamic factors underlying the Ln(III)/An(III) selectivity by C301 were further analyzed. A correlation between the thermodynamic trends and the coordination modes has been well established.

Structural and thermodynamic factors underlying the Ln(III)/An(III) selectivity by Di-2,4,4-trimethylpentyl dithiophosphinic acid

2019 Fall National Meeting

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