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Title: Influence of a Heterocyclic Nitrogen-Donor Group on the Coordination of Trivalent Actinides and Lanthanides by Aminopolycarboxylate Complexants

Abstract

Here, the novel metal chelator N-2-(pyridylmethyl)diethylenetriamine- N,N',N",N"-tetraacetic acid (DTTA-PyM) was designed to replace a single oxygen-donor acetate group of the well-known aminopolycarboxylate complexant diethylenetriamine- N,N,N',N",N"-pentaacetic acid (DTPA) with a nitrogen-donor 2-pyridylmethyl. Potentiometric, spectroscopic, computational, and radioisotope distribution methods show distinct differences for the 4f and 5f coordination environments and enhanced actinide binding due to the nitrogen-bearing heterocyclic moiety. The Am 3+, Cm 3+, and Ln 3+ complexation studies for DTTA-PyM reveal an enhanced preference, relative to DTPA, for trivalent actinide binding. Fluorescence studies indicate no changes to the octadentate coordination of trivalent curium, while evidence of heptadentate complexation of trivalent europium is found in mixtures containing EuHL (aq) complexes at the same aqueous acidity. The denticity change observed for Eu 3+ suggests that complex protonation occurs on the pyridyl nitrogen. Formation of the CmHL (aq) complex is likely due to the protonation of an available carboxylate group because the carbonyl oxygen can maintain octadentate coordination through a rotation. The observed suppressed protonation of the pyridyl nitrogen in the curium complexes may be attributed to stronger trivalent actinide binding by DTTA-PyM. Density functional theory calculations indicate that added stabilization of the actinide complexes with DTTA-PyM may originate from π-back-bonding interactions betweenmore » singly occupied 5f orbitals of Am 3+ and the pyridyl nitrogen. The differences between the stabilities of trivalent actinide chelates (Am 3+, Cm 3+) and trivalent lanthanide chelates (La 3+–Lu 3+) are observed in liquid–liquid extraction systems, yielding unprecedented 4f/5f differentiation when using DTTA-PyM as an aqueous holdback reagent. In addition, the enhanced nitrogen-donor softness of the new DTTA-PyM chelator was perturbed by adding a fluorine onto the pyridine group. The comparative characterization of N-(3-fluoro-2-pyridylmethyl)diethylenetriamine- N,N',N",N"-tetraacetic acid (DTTA-3-F-PyM) showed subdued 4 f/5 f differentiation due to the presence of this electron-withdrawing group.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [1]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1415903
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Inorganic Chemistry; Journal Volume: 57; Journal Issue: 3
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Grimes, Travis S., Heathman, Colt R., Jansone-Popova, Santa, Ivanov, Alexander S., Roy, Santanu, Bryantsev, Vyacheslav S., and Zalupski, Peter R. Influence of a Heterocyclic Nitrogen-Donor Group on the Coordination of Trivalent Actinides and Lanthanides by Aminopolycarboxylate Complexants. United States: N. p., 2018. Web. doi:10.1021/acs.inorgchem.7b02792.
Grimes, Travis S., Heathman, Colt R., Jansone-Popova, Santa, Ivanov, Alexander S., Roy, Santanu, Bryantsev, Vyacheslav S., & Zalupski, Peter R. Influence of a Heterocyclic Nitrogen-Donor Group on the Coordination of Trivalent Actinides and Lanthanides by Aminopolycarboxylate Complexants. United States. doi:10.1021/acs.inorgchem.7b02792.
Grimes, Travis S., Heathman, Colt R., Jansone-Popova, Santa, Ivanov, Alexander S., Roy, Santanu, Bryantsev, Vyacheslav S., and Zalupski, Peter R. Fri . "Influence of a Heterocyclic Nitrogen-Donor Group on the Coordination of Trivalent Actinides and Lanthanides by Aminopolycarboxylate Complexants". United States. doi:10.1021/acs.inorgchem.7b02792.
@article{osti_1415903,
title = {Influence of a Heterocyclic Nitrogen-Donor Group on the Coordination of Trivalent Actinides and Lanthanides by Aminopolycarboxylate Complexants},
author = {Grimes, Travis S. and Heathman, Colt R. and Jansone-Popova, Santa and Ivanov, Alexander S. and Roy, Santanu and Bryantsev, Vyacheslav S. and Zalupski, Peter R.},
abstractNote = {Here, the novel metal chelator N-2-(pyridylmethyl)diethylenetriamine-N,N',N",N"-tetraacetic acid (DTTA-PyM) was designed to replace a single oxygen-donor acetate group of the well-known aminopolycarboxylate complexant diethylenetriamine-N,N,N',N",N"-pentaacetic acid (DTPA) with a nitrogen-donor 2-pyridylmethyl. Potentiometric, spectroscopic, computational, and radioisotope distribution methods show distinct differences for the 4f and 5f coordination environments and enhanced actinide binding due to the nitrogen-bearing heterocyclic moiety. The Am3+, Cm3+, and Ln3+ complexation studies for DTTA-PyM reveal an enhanced preference, relative to DTPA, for trivalent actinide binding. Fluorescence studies indicate no changes to the octadentate coordination of trivalent curium, while evidence of heptadentate complexation of trivalent europium is found in mixtures containing EuHL(aq) complexes at the same aqueous acidity. The denticity change observed for Eu3+ suggests that complex protonation occurs on the pyridyl nitrogen. Formation of the CmHL(aq) complex is likely due to the protonation of an available carboxylate group because the carbonyl oxygen can maintain octadentate coordination through a rotation. The observed suppressed protonation of the pyridyl nitrogen in the curium complexes may be attributed to stronger trivalent actinide binding by DTTA-PyM. Density functional theory calculations indicate that added stabilization of the actinide complexes with DTTA-PyM may originate from π-back-bonding interactions between singly occupied 5f orbitals of Am3+ and the pyridyl nitrogen. The differences between the stabilities of trivalent actinide chelates (Am3+, Cm3+) and trivalent lanthanide chelates (La3+–Lu3+) are observed in liquid–liquid extraction systems, yielding unprecedented 4f/5f differentiation when using DTTA-PyM as an aqueous holdback reagent. In addition, the enhanced nitrogen-donor softness of the new DTTA-PyM chelator was perturbed by adding a fluorine onto the pyridine group. The comparative characterization of N-(3-fluoro-2-pyridylmethyl)diethylenetriamine-N,N',N",N"-tetraacetic acid (DTTA-3-F-PyM) showed subdued 4f/5f differentiation due to the presence of this electron-withdrawing group.},
doi = {10.1021/acs.inorgchem.7b02792},
journal = {Inorganic Chemistry},
number = 3,
volume = 57,
place = {United States},
year = {Fri Jan 05 00:00:00 EST 2018},
month = {Fri Jan 05 00:00:00 EST 2018}
}