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Title: An europium( iii ) diglycolamide complex: insights into the coordination chemistry of lanthanides in solvent extraction

Abstract

The synthesis, stoichiometry, and structural characterization of a homoleptic, cationic europium(III) complex with three neutral tetraalkyldiglycolamide ligands are reported. The tri(bismuth tetrachloride)tris(N,N,N',N'-tetra-n-octyldiglycolamide)Eu salt, [Eu(TODGA)3][(BiCl4)3] obtained from methanol was examined by Eu L3-edge X-ray absorption spectroscopy (XAS) to reveal an inner-sphere coordination of Eu3+ that arises from 9 O atoms and two next-nearest coordination spheres that arise from 6 carbon atoms each. A structural model is proposed in which each TODGA ligand with its O[double bond, length as m-dash]Ca–Cb–O–Cb–Ca[double bond, length as m-dash]O backbone acts as a tridentate O donor, where the two carbonyl O atoms and the one ether O atom bond to Eu3+. Given the structural rigidity of the tridentate coordination motif in [Eu(TODGA)3]3+ with six 5-membered chelate rings, the six Eu–Ca and six Eu–Cb interactions are readily resolved in the EXAFS (extended X-ray absorption fine structure) spectrum. The three charge balancing [BiCl4]- anions are beyond the cationic [Eu(TODGA)3]3+ cluster in an outer sphere environment that is too distant to be detected by XAS. Despite their sizeable length and propensity for entanglement, the four n-octyl groups of each TODGA (for a total of twelve) do not perturb the Eu3+ coordination environment over that seen from previously reported single-crystal structuresmore » of tripositive lanthanide (Ln3+) complexes with tetraalkyldiglycolamide ligands (of the same 1 : 3 metal-to-ligand ratio stoichiometry) but having shorter i-propyl and i-butyl groups. The present results set the foundation for understanding advanced solvent extraction processes for the separation of the minor, tripositive actinides (Am, Cm) from the Ln3+ ions in terms of the local structure of Eu3+ in a solid state coordination complex with TODGA.« less

Authors:
; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science - Office of Basic Energy Sciences - Chemical Sciences, Geosciences, and Biosciences Division
OSTI Identifier:
1392647
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Dalton Transactions; Journal Volume: 44; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; EXAFS; bismuth tetrachloride; coordination chemistry; inner-sphere; lanthanide; liquid-liquid extraction; outer-sphere; tetraalkyldiglycolamides

Citation Formats

Antonio, Mark R., McAlister, Daniel R., and Horwitz, E. Philip. An europium( iii ) diglycolamide complex: insights into the coordination chemistry of lanthanides in solvent extraction. United States: N. p., 2015. Web. doi:10.1039/c4dt01775g.
Antonio, Mark R., McAlister, Daniel R., & Horwitz, E. Philip. An europium( iii ) diglycolamide complex: insights into the coordination chemistry of lanthanides in solvent extraction. United States. doi:10.1039/c4dt01775g.
Antonio, Mark R., McAlister, Daniel R., and Horwitz, E. Philip. Thu . "An europium( iii ) diglycolamide complex: insights into the coordination chemistry of lanthanides in solvent extraction". United States. doi:10.1039/c4dt01775g.
@article{osti_1392647,
title = {An europium( iii ) diglycolamide complex: insights into the coordination chemistry of lanthanides in solvent extraction},
author = {Antonio, Mark R. and McAlister, Daniel R. and Horwitz, E. Philip},
abstractNote = {The synthesis, stoichiometry, and structural characterization of a homoleptic, cationic europium(III) complex with three neutral tetraalkyldiglycolamide ligands are reported. The tri(bismuth tetrachloride)tris(N,N,N',N'-tetra-n-octyldiglycolamide)Eu salt, [Eu(TODGA)3][(BiCl4)3] obtained from methanol was examined by Eu L3-edge X-ray absorption spectroscopy (XAS) to reveal an inner-sphere coordination of Eu3+ that arises from 9 O atoms and two next-nearest coordination spheres that arise from 6 carbon atoms each. A structural model is proposed in which each TODGA ligand with its O[double bond, length as m-dash]Ca–Cb–O–Cb–Ca[double bond, length as m-dash]O backbone acts as a tridentate O donor, where the two carbonyl O atoms and the one ether O atom bond to Eu3+. Given the structural rigidity of the tridentate coordination motif in [Eu(TODGA)3]3+ with six 5-membered chelate rings, the six Eu–Ca and six Eu–Cb interactions are readily resolved in the EXAFS (extended X-ray absorption fine structure) spectrum. The three charge balancing [BiCl4]- anions are beyond the cationic [Eu(TODGA)3]3+ cluster in an outer sphere environment that is too distant to be detected by XAS. Despite their sizeable length and propensity for entanglement, the four n-octyl groups of each TODGA (for a total of twelve) do not perturb the Eu3+ coordination environment over that seen from previously reported single-crystal structures of tripositive lanthanide (Ln3+) complexes with tetraalkyldiglycolamide ligands (of the same 1 : 3 metal-to-ligand ratio stoichiometry) but having shorter i-propyl and i-butyl groups. The present results set the foundation for understanding advanced solvent extraction processes for the separation of the minor, tripositive actinides (Am, Cm) from the Ln3+ ions in terms of the local structure of Eu3+ in a solid state coordination complex with TODGA.},
doi = {10.1039/c4dt01775g},
journal = {Dalton Transactions},
number = 2,
volume = 44,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 2015},
month = {Thu Jan 01 00:00:00 EST 2015}
}