Effect of f-element complexation on the radiolysis of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP])

Stephen P. Mezyk; Makayla Baxter; Cristian Celis-Barros; Travis S. Grimes; Peter R. Zalupski; Cathy Rae; Christopher A. Zarzana; Andrew R. Cook; Gregory P. Horne

doi:10.1039/d4dt00424h

Effect of f-element complexation on the radiolysis of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP])

Stephen P. Mezyk, Makayla Baxter, Cristian Celis-Barros, Travis S. Grimes, Peter R. Zalupski, Cathy Rae, Christopher A. Zarzana, Andrew R. Cook, Gregory P. Horne

Radiochemical Process Development

Research output: Contribution to journal › Article › peer-review

Abstract

A systematic study of the impact on the chemical reactivity of the oxidising n-dodecane radical cation (RH˙⁺) with f-element complexed 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) has been undertaken utilizing time-resolved electron pulse radiolysis/transient absorption spectroscopy and high-level quantum mechanical calculations. Lanthanide ion complexed species, [Ln((HEH[EHP])₂)₃], exhibited vastly increased reactivity (over 10× faster) in comparison to the non-complexed ligand in n-dodecane solvent, whose rate coefficient was k = (4.66 ± 0.22) × 10⁹ M⁻¹ s⁻¹. Similar reactivity enhancement was also observed for the corresponding americium ion complex, k = (5.58 ± 0.30) × 10¹⁰ M⁻¹ s⁻¹. The vastly increased reactivity of these f-element complexes was not due to simple increased diffusion-control of these reactions; rather, enhanced hole transfer mechanisms for the complexes were calculated to become energetically more favourable. Interestingly, the observed reactivity trend with lanthanide ion size was not linear; instead, the rate coefficients showed an initial increase (Lu to Yb) followed by a decrease (Tm to Ho), followed by another increase (Dy to La). This behaviour was excellently predicted by the calculated reaction volumes of these complexes. Complementary cobalt-60 gamma irradiations for select lanthanide complexes demonstrated that the measured kinetic differences translated to increased ligand degradation at steady-state timescales, affording ∼38% increase in ligand loss of a 1 : 1 [La((HEH[EHP])₂)₃] : HEH[EHP] ratio system.

Original language	English
Pages (from-to)	6881-6891
Number of pages	11
Journal	Dalton Transactions
Volume	53
Issue number	16
DOIs	https://doi.org/10.1039/d4dt00424h
State	Published - Feb 26 2024

Funding

This research has been funded by the United States Department of Energy (U.S. DOE) Assistant Secretary for Nuclear Energy, under the Material Recovery and Waste Form Development Campaign, DOE-Idaho Operations Office Contract DE-AC07-05ID14517 and DE-NE0008406 Nuclear Energy Universities Program (NEUP) grant. Cook and electron pulse irradiation experiments at LEAF of the BNL Accelerator Centre for Energy Research were supported by the U.S. DOE, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract DE-SC0012704. Baxter was supported by the U.S. DOE, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internships Program (SULI).

Funders	Funder number
Office of Workforce Development for Teachers
U.S. Department of Energy	DE-AC07-05ID14517, DE-NE0008406
Office of Science
Basic Energy Sciences
Chemical Sciences, Geosciences, and Biosciences Division	DE-SC0012704

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@article{6244e0be7d09481f8c31d273664f1078,

title = "Effect of f-element complexation on the radiolysis of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP])",

abstract = "A systematic study of the impact on the chemical reactivity of the oxidising n-dodecane radical cation (RH˙+) with f-element complexed 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) has been undertaken utilizing time-resolved electron pulse radiolysis/transient absorption spectroscopy and high-level quantum mechanical calculations. Lanthanide ion complexed species, [Ln((HEH[EHP])2)3], exhibited vastly increased reactivity (over 10× faster) in comparison to the non-complexed ligand in n-dodecane solvent, whose rate coefficient was k = (4.66 ± 0.22) × 109 M−1 s−1. Similar reactivity enhancement was also observed for the corresponding americium ion complex, k = (5.58 ± 0.30) × 1010 M−1 s−1. The vastly increased reactivity of these f-element complexes was not due to simple increased diffusion-control of these reactions; rather, enhanced hole transfer mechanisms for the complexes were calculated to become energetically more favourable. Interestingly, the observed reactivity trend with lanthanide ion size was not linear; instead, the rate coefficients showed an initial increase (Lu to Yb) followed by a decrease (Tm to Ho), followed by another increase (Dy to La). This behaviour was excellently predicted by the calculated reaction volumes of these complexes. Complementary cobalt-60 gamma irradiations for select lanthanide complexes demonstrated that the measured kinetic differences translated to increased ligand degradation at steady-state timescales, affording ∼38% increase in ligand loss of a 1 : 1 [La((HEH[EHP])2)3] : HEH[EHP] ratio system.",

author = "Mezyk, {Stephen P.} and Makayla Baxter and Cristian Celis-Barros and Grimes, {Travis S.} and Zalupski, {Peter R.} and Cathy Rae and Zarzana, {Christopher A.} and Cook, {Andrew R.} and Horne, {Gregory P.}",

note = "Publisher Copyright: {\textcopyright} 2024 The Royal Society of Chemistry.",

year = "2024",

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day = "26",

doi = "10.1039/d4dt00424h",

language = "English",

volume = "53",

pages = "6881--6891",

journal = "Dalton Transactions",

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T1 - Effect of f-element complexation on the radiolysis of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP])

AU - Mezyk, Stephen P.

AU - Baxter, Makayla

AU - Celis-Barros, Cristian

AU - Grimes, Travis S.

AU - Zalupski, Peter R.

AU - Rae, Cathy

AU - Zarzana, Christopher A.

AU - Cook, Andrew R.

AU - Horne, Gregory P.

PY - 2024/2/26

Y1 - 2024/2/26

N2 - A systematic study of the impact on the chemical reactivity of the oxidising n-dodecane radical cation (RH˙+) with f-element complexed 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) has been undertaken utilizing time-resolved electron pulse radiolysis/transient absorption spectroscopy and high-level quantum mechanical calculations. Lanthanide ion complexed species, [Ln((HEH[EHP])2)3], exhibited vastly increased reactivity (over 10× faster) in comparison to the non-complexed ligand in n-dodecane solvent, whose rate coefficient was k = (4.66 ± 0.22) × 109 M−1 s−1. Similar reactivity enhancement was also observed for the corresponding americium ion complex, k = (5.58 ± 0.30) × 1010 M−1 s−1. The vastly increased reactivity of these f-element complexes was not due to simple increased diffusion-control of these reactions; rather, enhanced hole transfer mechanisms for the complexes were calculated to become energetically more favourable. Interestingly, the observed reactivity trend with lanthanide ion size was not linear; instead, the rate coefficients showed an initial increase (Lu to Yb) followed by a decrease (Tm to Ho), followed by another increase (Dy to La). This behaviour was excellently predicted by the calculated reaction volumes of these complexes. Complementary cobalt-60 gamma irradiations for select lanthanide complexes demonstrated that the measured kinetic differences translated to increased ligand degradation at steady-state timescales, affording ∼38% increase in ligand loss of a 1 : 1 [La((HEH[EHP])2)3] : HEH[EHP] ratio system.

AB - A systematic study of the impact on the chemical reactivity of the oxidising n-dodecane radical cation (RH˙+) with f-element complexed 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) has been undertaken utilizing time-resolved electron pulse radiolysis/transient absorption spectroscopy and high-level quantum mechanical calculations. Lanthanide ion complexed species, [Ln((HEH[EHP])2)3], exhibited vastly increased reactivity (over 10× faster) in comparison to the non-complexed ligand in n-dodecane solvent, whose rate coefficient was k = (4.66 ± 0.22) × 109 M−1 s−1. Similar reactivity enhancement was also observed for the corresponding americium ion complex, k = (5.58 ± 0.30) × 1010 M−1 s−1. The vastly increased reactivity of these f-element complexes was not due to simple increased diffusion-control of these reactions; rather, enhanced hole transfer mechanisms for the complexes were calculated to become energetically more favourable. Interestingly, the observed reactivity trend with lanthanide ion size was not linear; instead, the rate coefficients showed an initial increase (Lu to Yb) followed by a decrease (Tm to Ho), followed by another increase (Dy to La). This behaviour was excellently predicted by the calculated reaction volumes of these complexes. Complementary cobalt-60 gamma irradiations for select lanthanide complexes demonstrated that the measured kinetic differences translated to increased ligand degradation at steady-state timescales, affording ∼38% increase in ligand loss of a 1 : 1 [La((HEH[EHP])2)3] : HEH[EHP] ratio system.

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U2 - 10.1039/d4dt00424h

DO - 10.1039/d4dt00424h

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AN - SCOPUS:85188205130

SN - 1477-9226

VL - 53

SP - 6881

EP - 6891

JO - Dalton Transactions

JF - Dalton Transactions

IS - 16

ER -

Effect of f-element complexation on the radiolysis of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP])

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