Role of diluent in the unusual extraction of Am3+ and Eu3+ ions with benzene-centered tripodal diglycolamides: local structure studies using luminescence spectroscopy and XAS.

Two benzene-centered tripodal diglycolamide ligands (LI and LII) were used for the extraction of Am3+ and Eu3+ from nitric acid solutions into a diluent medium of n-dodecane modified with various amounts of isodecanol. The ligands showed preferential extraction of Eu3+ over Am3+ in most cases. While the extraction of the Am3+ ion was not much affected (with a slight increase) over the entire range of diluent compositions in the case of LI, a gradual decline in the extraction of the Eu3+ ion suggested a reversal in the separation trend with Am3+ being preferentially extracted with a solution of LI in pure isodecanol. On the other hand, a sharp decline was seen for the extraction of both Am3+ and Eu3+ in the entire range of diluents containing various fractions of isodecanol when LII was used. The unusual extraction was attributed to the difference in the complexation behaviour of LI and LII, which was explained on the basis of photoluminescence (PL) spectroscopy as well as XAS studies. The PL studies suggested absence of any inner-sphere water molecules from the lifetime data, while the splitting of emisison peaks and asymmetry ratio values gave an idea about the complex geometry. On the other hand, the XAS studies gave information about the bonding in the coordination complexes. [ABSTRACT FROM AUTHOR]