TRLFS study on the complexation of Cm(iii) and Eu(iii) with SO3-Ph-BTBP

Abstract

The complexation of Cm(III) and Eu(III) with a water soluble BTBP (sodium 3,3′,3′′,3′′′-([2,2′-bipyridine]-6,6′-diylbis(1,2,4-triazine-3,5,6-triyl))tetrabenzenesulfonate, SO₃-Ph-BTBP) is studied using time resolved laser fluorescence spectroscopy. For the complexation of Cm(III) the influence of the medium (10⁻³ M HClO₄ → 0.5 M HNO₃) is investigated in detail revealing important impacts of the applied medium (pH, ionic strength, anions) on the speciation and conditional stability constants. SO₃-Ph-BTBP forms 1 : 2 complexes with Cm(III) and Eu(III). The conditional stability constants of [Cm(SO₃-Ph-BTBP)₂]⁵⁻ and [Eu(SO₃-Ph-BTBP)₂]⁵⁻ in 0.5 M HNO₃ are determined to be log β₀₂ = 7.3 ± 0.3 and log β₀₂ = 5.4 ± 0.5, respectively. The difference of 1.9 orders of magnitude is in line with hydrophobic BT(B)P type ligands and shows that the selectivity is not affected by tuning the hydrophilicity using SO₃-Ph-side chains.