| Autor: |
Jensen MP; Chemical Sciences and Engineering Division, Argonne National Laboratory , 9700 S. Cass Ave., Argonne, Illinois 60439, United States., Chiarizia R, Shkrob IA, Ulicki JS, Spindler BD, Murphy DJ, Hossain M, Roca-Sabio A, Platas-Iglesias C, de Blas A, Rodríguez-Blas T |
| Jazyk: |
angličtina |
| Zdroj: |
Inorganic chemistry [Inorg Chem] 2014 Jun 16; Vol. 53 (12), pp. 6003-12. Date of Electronic Publication: 2014 Jun 03. |
| DOI: |
10.1021/ic500244p |
| Abstrakt: |
Complexation of the adjacent actinide ions americium(III) and curium(III) by the ligand N,N'-bis[(6-carboxy-2-pyridyl)methyl]-1,10-diaza-18-crown-6 (H2bp18c6) in aqueous solution was studied to quantify and characterize its americium/curium selectivity. Liquid-liquid extraction and spectrophotometric titration indicated the presence of both fully deprotonated and monoprotonated complexes, An(bp18c6)(+) and An(Hbp18c6)(2+) (An = Am or Cm), at the acidities that would be encountered when treating nuclear wastes. The stability constants of the complexes in 1 M NaNO3 determined using competitive complexation were log β101 = 15.49 ± 0.06 for Am and 14.88 ± 0.03 for Cm, indicating a reversal of the usual order of complex stability, where ligands bind the smaller Cm(III) ion more tightly than Am(III). The Am/Cm selectivity of bp18c6(2-) that is defined by the ratio of the Am and Cm stability constants (β101 Am/β101 Cm = 4.1) is the largest reported so far for binary An(III)-ligand complexes. Theoretical density functional theory calculations using the B3LYP functional suggest that the ligand's size-selectivity for larger 4f- and 5f-element cations arises from steric constraints in the crown ether ring. Enhanced 5f character in molecular orbitals involving actinide-nitrogen interactions is predicted to favor actinide(III) complexation by bp18c6(2-) over the complexation of similarly sized lanthanide(III) cations. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
|
