Charakterisierung von f-Element-Komplexen mit soft donor-Liganden

In recent years, European research projects have investigated the possibility of sepa-rating not only uranium and plutonium but also americium from irradiated nuclear fuel. A particular challenge here is the separation of the trivalent actinides Am(III) and Cm(III) from each other and from the chemically similar trivalent fission lanthanides. A suitable complexant for this purpose is the hydrophilic Am(III)-selective N-donor ligand SO3-Ph-BTBP (tetrasodium-3,3',3'',3'''-([2,2'-bipyridine]-6,6'-diylbis(1,2,4-triazine-3,5,6-triyl))tetrabenzenesulfonate), which can be used to separate Am(III) from other trivalent metals by smart combination with diglycolamide ligands as extractants. In this work, the extraction behavior of the diglycolamides TODGA (N,N,N',N'-tetraoctyl di-glycolamide) and the mono- and dimethylated derivatives Me-TODGA and Me2-TODGA, respectively, were investigated. The influence of changes in the acid and lig-and concentrations and the influence of the acid anion were studied. Combining the diglycolamides with SO3-Ph-BTBP in the HNO3 system significantly increased the se-lectivity of Ln(III) over An(III) as well as Cm(III) over Am(III), with maximum separation factors SFEu(III)/Am(III) of 629 ± 89 for TODGA, 237 ± 34 for Me-TODGA and 37 ± 5 for Me2-TODGA, as well as SFCm(III)/Am(III) of 2.6 ± 0.4 for TODGA, 2.0 ± 0.3 for Me-TODGA and 1.2 ± 0.2 for Me2-TODGA. Moreover, an unexpected effect was revealed for the heavier lanthanides, which was further elucidated by speciation studies of various Ln(III)-SO3-Ph-BTBP complexes using UV/Vis spectroscopy. The formation of 1:2 complexes (metal-to-ligand ratio) with SO3-Ph-BTBP was confirmed for the three lan-thanides studied (Eu(III), Nd(III) and Ho(III)) and stability constants log β2 of 7.3 ± 0.7 (Eu(III) in water), 8.0 ± 0.8 (Nd(III) in 10-3 mol L-1 HNO3) and 6.1 ± 0.4 (Ho(III) in 3 mol L-1 HNO3) were determined. Conclusively, a first extraction series was performed with the newly synthesized CHON-compatible N-donor ligand BPTD (3,3'-([2,2'-bipyridine]-6-6'-diylbis(1H-1,2,3-triazole-4,1-diyl))bis(propan-1-ol)). Maximum separation factors SFEu(III)/Am(III) of 221 ± 31 and SFCm(III)/Am(III) of 2.1 ± 0.3 were obtained, which are lower compared to SO3-Ph-BTBP, but nevertheless quite promising for further investigations