A diglycolamide-functionalized TREN-based dendrimer with a 'crab-like' grip for the complexation of actinides and lanthanides.

A generation 1 dendrimer, based on tris(2-aminoethyl)amine (TREN), containing six diglycolamide (DGA) pendent arms (termed TREN-G1-DGA) was synthesized and evaluated for the extraction of actinides and fission product ions. Solvent extraction studies indicated preferential extraction of Eu3+ over Am3+ with a separation factor value of ca. 4.5 in line with the extraction behaviour of multiple DGA ligands in previous reports. The distribution values of Am3+ and Eu3+ were about 12 and 9 times higher, respectively, than those obtained in the case of TREN-DGA using the 1 × 10-3 M ligand in 5% iso-decanol/95% n-dodecane at 3 M HNO3. The 1 : 1 (M : L) extracted species suggested 'inclusion' complex formation where more than one DGA moiety participates in the complex formation. The extracted species were devoid of any inner-sphere coordinated water molecules as confirmed by luminescence spectroscopy. The structure of the complex was also studied by DFT computations and EXAFS which suggested binding of three DGA arms around the central metal ion in the absence of any inner-sphere nitrate ions.

Separation of Am3+ and Eu3+ using hexa-n-octylnitrilo triacetamide (HONTA): complexation, extraction, luminescence, EXAFS and DFT studies.

This paper reports the solvent extraction of Am3+ and Eu3+ using N,N,N',N',N'',N''-hexa-n-octylnitrilotriacetamide (HONTA) as the extractant in n-dodecane. The results are in variance with those reported previously with respect to the nature of the extracted species. The solvent extraction data were entirely different from those reported previously as the extracted species conformed to 1 : 2 (M : L) species for both Am3+ and Eu3+ ions. The structure of the extracted complex was determined by EXAFS demonstrating the three amidic 'O' atoms of the HONTA complex with the Eu3+ ion. In the case of the Am3+ ion, the pivotal 'N' atom is suggested to bond to the metal ion, which may explain the significantly more favourable extraction of Am3+vis-à-vis Eu3+. The absence of H2O molecules in the inner coordination sphere of the Eu3+-HONTA extract was confirmed by luminescence spectroscopic measurements. Complexation studies in MeOH and EtOH indicated the formation of both 1 : 1 and 1 : 2 complexes with Nd3+ ions. The results are explained on the basis of DFT calculations using HMNTA, the corresponding hexamethyl analogue of HONTA.

Unique selectivity reversal in Am(3+)-Eu(3+) extraction in a tripodal TREN-based diglycolamide in ionic liquid: extraction, luminescence, complexation and structural studies.

An N-pivot diglycolamide extractant (DGA-TREN) was synthesized for the first time and its complexation behaviour was studied towards trivalent lanthanide/actinide ions. The solvent extraction studies suggested a unique selectivity reversal in the extraction of trivalent actinides versus trivalent lanthanides which was observed performing extraction studies in an ionic liquid vis-à-vis a molecular diluent for a tripodal TREN-based diglycolamide ligand (DGA-TREN) vs. a tripodal diglycolamide ligand (T-DGA) which may have great significance in radioactive waste remediation. The nature of the bonding to Eu(3+) ion was investigated by EXAFS as well as by DFT calculations.