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Bistriazinyl-pyridine type ligands are important extracting agents for separating trivalent actinide ions from trivalent lanthanides. The alkyl substituents on the lateral triazine rings have a significant effect on the stability of the ligand against hydrolysis and radiolysis. Furthermore they influence solubility, extraction behaviour and selectivity. TRLFS and extraction studies suggest differences in complexation and extraction behaviour of BTP ligands bearing iso -propyl or n -propyl substituents, respectively. As NMR studies allow insight into the metal-ligand bonding, we conducted NMR studies on a range of 15 N-labelled n PrBTP and i PrBTP Ln(III) and Am(III) complexes. Our results show that no strong change in the metal-ligand bonding occurs, thus excluding electronic reasons for differences in complexation behaviour, extraction kinetics and selectivity. This supports mechanistic reasons for the observed differences. [ABSTRACT FROM AUTHOR]

Abstract: In this study the separation of Am(III) from Eu(III) in nitric acid using two BTP-type N-donor ligands, 2,6-bis(6-ethyl-1,2–diazine-3-yl)pyridine (Et-BDP) and 2,6-bis(4- n propyl-2,3,5,6-tetrazine-1-yl)pyridine ( n Pr-tetrazine) is presented. The extraction and separation properties of both ligands are tested by two phase liquid-liquid extraction at different acid concentrations. In contrast to n Pr-BTP the bisdiazinyl ligand Et-BDP is prone to protonation at nitric acid concentrations of 0.2M and higher. A separation factor of SFAm/Eu ≈ 5 is obtained using Et-BDP as extracting ligand and with n Pr-tetrazine a SFAm/Eu of 9.1 is realized. Hereby 2-bromodecanoic acid as lipophilic anion source is needed. [Copyright &y& Elsevier]