RESUMO
Complexation of Pu(iv) with the actinide extractant CyMe4-BTPhen (2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline) was followed by vis-NIR spectroscopy in acetonitrile solution. The solid-state structure of the crystallized product suggests that Pu(iv) is reduced to Pu(iii) upon complexation. Analysis by DFT modeling is consistent with metal-based rather than ligand-based reduction.
RESUMO
The complexation of Cm(III) and Eu(III) with 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4-BTPhen) and 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2'-bipyridine (CyMe4-BTBP) in methanolic solution was investigated by TRLFS. For both ligands, the 1:2 complex with the particular metal ion is the only species observed in equilibrated samples. The species distribution for various ligand concentrations was determined and stability constants of the 1:2 complexes were derived (log ß2 = 13.8 ± 0.2 (Cm(III)-CyMe4-BTPhen), log ß2 = 11.6 ± 0.4 (Eu(III)-CyMe4-BTPhen), log ß2 = 12.4 ± 0.3 (Cm(III)-CyMe4-BTBP) and log ß2 = 11.3 ± 0.3 (Eu(III)-CyMe4-BTBP)). Biphasic experiments in combination with TRLFS studies on the organic phase revealed the formation of ternary complexes with two CyMe4-BTPhen or -BTBP molecules and additional coordination of a nitrate anion as species formed during the extraction process.
RESUMO
Lanthanide(III) complexes with N-donor extractants, which exhibit the potential for the separation of minor actinides from lanthanides in the management of spent nuclear fuel, have been directly synthesized and characterized in both solution and solid states. Crystal structures of the Pr(3+), Eu(3+), Tb(3+), and Yb(3+) complexes of 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline (CyMe4-BTPhen) and the Pr(3+), Eu(3+), and Tb(3+) complexes of 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2'-bypyridine (CyMe4-BTBP) were obtained. The majority of these structures displayed coordination of two of the tetra-N-donor ligands to each Ln(3+) ion, even when in some cases the complexations were performed with equimolar amounts of lanthanide and N-donor ligand. The structures showed that generally the lighter lanthanides had their coordination spheres completed by a bidentate nitrate ion, giving a 2+ charged complex cation, whereas the structures of the heavier lanthanides displayed tricationic complex species with a single water molecule completing their coordination environments. Electronic absorption spectroscopic titrations showed formation of the 1:2 Ln(3+)/L(N4-donor) species (Ln = Pr(3+), Eu(3+), Tb(3+)) in methanol when the N-donor ligand was in excess. When the Ln(3+) ion was in excess, evidence for formation of a 1:1 Ln(3+)/L(N4-donor) complex species was observed. Luminescent lifetime studies of mixtures of Eu(3+) with excess CyMe4-BTBP and CyMe4-BTPhen in methanol indicated that the nitrate-coordinated species is dominant in solution. X-ray absorption spectra of Eu(3+) and Tb(3+) species, formed by extraction from an acidic aqueous phase into an organic solution consisting of excess N-donor extractant in pure cyclohexanone or 30% tri-n-butyl phosphate (TBP) in cyclohexanone, were obtained. The presence of TBP in the organic phase did not alter lanthanide speciation. Extended X-ray absorption fine structure data from these spectra were fitted using chemical models established by crystallography and solution spectroscopy and showed the dominant lanthanide species in the bulk organic phase was a 1:2 Ln(3+)/L(N-donor) species.
