Comparative NMR Study of nPrBTP and iPrBTP Complexes


Comparative NMR Study of nPrBTP and iPrBTP Complexes

Adam, C.; Rohde, V.; Müllich, U.; Kaden, P.; Geist, A.; Panak, P. J.

Partitioning and transmutation (P&T) is a strategy for reducing the long-term radiotoxicity and heat load of spent nuclear fuel by separating actinides from the used fuel and converting them into shorterlived or stable products. A key step in this process is the separation of the trivalent actinides from lanthanides, which can be achieved by liquid-liquid extraction using selective N-donor extracting ligands, such as alkylated bis-triazinyl pyridines (BTP). These have high separation factors (>100) for trivalent americium over europium. However, little is known about the molecular origin of their selectivity.
The aliphatic side chains of BTP ligands influence the stability against radiation and hydrolysis, the solubility, but also the selectivity and extraction behaviour. While nPrBTP (1) has been thoroughly studied over the past years, only few data are available for its isomer iPrBTP (2). TRLFS studies showed that the stability constants for the Eu(III) complex are almost three orders of magnitude higher than for nPrBTP, while the increase for Cm(III) complexes is less pronounced.
This result prompted us to investigate Ln(III) and the Am(III) complexes by NMR spectroscopy, which offers insight into the metal-ligand bond properties. For the NMR studies, iPrBTP with 15N isotope labelling of the nitrogen atoms in the pyrazole moiety was synthesized. We will show a comparison of the bonding properties in complexes of (1) and (2) and discuss the share of covalence in the bonding. Furthermore, the implications for the mechanism of complex formation with ligand (2) will be evaluated.

Keywords: NMR Spectroscopy; Separation; Partitioning Ligands; Bonding

  • Lecture (Conference)
    ATALANTE 2016 – Nuclear Chemistry for Sustainable Fuel Cycles, 05.-10.06.2016, Montpellier, Frankreich

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Publ.-Id: 23648