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Dutra FR, Vasiliu M, Gomez AN, Xia D, Dixon DA. Prediction of Redox Potentials for U, Np, Pu, and Am in Aqueous Solution. J Phys Chem A 2024; 128:5612-5626. [PMID: 38959054 DOI: 10.1021/acs.jpca.4c02902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/04/2024]
Abstract
The redox properties of the actinides in aqueous solution are important for fuel production/reprocessing and understanding the environmental impact of nuclear waste. The redox potentials for U, Np, Pu, and Am in oxidation states from 0 up to VII (as appropriate) in aqueous solutions have been predicted at the density functional theory level with the B3LYP functional, Stuttgart small core pseudopotential basis sets for the actinides, and explicit (30H2O molecules)/implicit treatment of the aqueous solvent using the self-consistent reaction field COSMO and SMD approaches for the implicit solvation. The predictions of the structural parameters of clusters incorporating first and second solvation shells are consistent with the available experimental data. Our results are typically within 0.2 V of the available experimental data using two explicit solvation shells with an implicit solvent model. The use of the PW91 functional substantially improved the prediction of the Pu(VI/V) redox couple. The redox couples for An(VI/IV) and An(V/IV) which involve the addition of protons and removal of the actinyl oxygens led to slightly larger differences from an experiment. The An(IV/0) and An(III/0) couples were reliably predicted with our approach. Predictions of the unknown An(II/I) redox potentials were negative, consistent with expectations, and predictions for unknown An(VII/VI), An(III/II), and An(II/0) redox couples improve prior estimates.
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Affiliation(s)
- Felipe R Dutra
- Instituto de Química, Universidade Estadual de Campinas, Barão Geraldo, P.O. Box 6154, Campinas 13083-970, São Paulo, Brazil
- Department of Chemistry and Biochemistry, The University of Alabama, Shelby Hall, Tuscaloosa, Alabama 35487-0336, United States
| | - Monica Vasiliu
- Department of Chemistry and Biochemistry, The University of Alabama, Shelby Hall, Tuscaloosa, Alabama 35487-0336, United States
| | - Amber N Gomez
- Department of Chemistry and Biochemistry, The University of Alabama, Shelby Hall, Tuscaloosa, Alabama 35487-0336, United States
| | - Donna Xia
- Department of Chemistry and Biochemistry, The University of Alabama, Shelby Hall, Tuscaloosa, Alabama 35487-0336, United States
| | - David A Dixon
- Department of Chemistry and Biochemistry, The University of Alabama, Shelby Hall, Tuscaloosa, Alabama 35487-0336, United States
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Yan X, Jiang H, Liu Z, Wang D. Computational Comparative Study of the Binding of Americium with N-Donor Ligands. Inorg Chem 2024; 63:8206-8214. [PMID: 38647176 DOI: 10.1021/acs.inorgchem.4c00448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
The accessibility of multiple valence states of americium (Am) inspired redox-based protocols aimed at efficient separation of trivalent Am (Am3+) from trivalent lanthanides (Ln3+) alternative to the traditional liquid-liquid extraction. This requires an extensive understanding of the coordination chemistry of Am in its various accessible valence states in the aqueous phase. In this work, by means of DFT calculations, the coordination of AmIII-VI with five typical N-donor ligands, i.e., terpyridine (tpy), bispyrazinylpyridine (dpp), bistriazinylpyridine (BTP), bistriazinyl bipyridine (BTBP), and bistrazinyl phenanthroline (BTPhen), was studied in terms of energy and topological analysis. The results show that the exchange of aqua ligands of hydrated ions by N-donor ligands is an entropy-driven process and enthalpically unfavorable. Topological analysis suggests a distinct mechanism of BTP to modulate the redox potential of Am(III) in that BTP can assist the relay of the leaving electron of AmIII, while the other N-donor ligands can detain the oxidation of Am by offering their electron instead. This comparative study enriches our understanding of the coordination chemistry of high-valent Am with N-donor ligands and recommends the ligand design toward the modulation of redox potentials of hydrated Am(III) ions.
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Affiliation(s)
- Xin Yan
- State Key Laboratory of Fine Chemicals, Liaoning Key Laboratory for Catalytic Conversion of Carbon Resources, School of Chemistry, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China
| | - Hui Jiang
- State Key Laboratory of Fine Chemicals, Liaoning Key Laboratory for Catalytic Conversion of Carbon Resources, School of Chemistry, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China
| | - Ziyi Liu
- State Key Laboratory of Fine Chemicals, Liaoning Key Laboratory for Catalytic Conversion of Carbon Resources, School of Chemistry, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China
| | - Dongqi Wang
- State Key Laboratory of Fine Chemicals, Liaoning Key Laboratory for Catalytic Conversion of Carbon Resources, School of Chemistry, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China
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Rice NT, Dalodière E, Adelman SL, Jones ZR, Kozimor SA, Mocko V, Root HD, Stein BW. Oxidizing Americium(III) with Sodium Bismuthate in Acidic Aqueous Solutions. Inorg Chem 2022; 61:12948-12953. [PMID: 35939562 DOI: 10.1021/acs.inorgchem.2c01596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Historic perspectives describing f-elements as being redox "inactive" are fading. Researchers continue to discover new oxidation states that are not as inaccessible as once assumed for actinides and lanthanides. Inspired by those contributions, we studied americium(III) oxidation in aqueous media under air using NaBiO3(s). We identified selective oxidation of Am3+(aq) to AmO22+(aq) or AmO21+(aq) could be achieved by changing the aqueous matrix identity. AmO22+(aq) formed in H3PO4(aq) (1 M) and AmO21+(aq) formed in dilute HCl(aq) (0.1 M). These americyl products were stable for weeks in solution. Also included is a method to recover 243Am from the americium and bismuth mixtures generated during these studies.
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Affiliation(s)
- Natalie T Rice
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Elodie Dalodière
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Sara L Adelman
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Zachary R Jones
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Stosh A Kozimor
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Veronika Mocko
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Harrison D Root
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Benjamin W Stein
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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Jennifer G A, Gao Y, Schreckenbach G, Varathan E. Chemical bonding in actinyl(V/VI) dipyriamethyrin complexes for the actinide series from americium to californium: a computational investigation. Dalton Trans 2022; 51:10006-10019. [PMID: 35703365 DOI: 10.1039/d2dt01142e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The separation of minor actinides in their dioxocation (i.e., actinyl) form in high-valence oxidation states requires efficient ligands for their complexation. In this work, we evaluate the complexation properties of actinyls including americyl, curyl, berkelyl, and californyl in their pentavalent and hexavalent oxidation states with the dipyriamethyrin ligand (L) using density functional theory calculations. The calculated bond parameters show shorter AnOyl bonds with covalent character and longer An-N bonds with ionic character. The bonding between the actinyl cation and the ligand anion shows a flow of charges from the ligand to actinyl in all [AnV/VIO2-L]1-/0 complexes. However, across the series, backdonation of charges from the metal to the ligand becomes prominent and stabilizes the complexes. The thermodynamic parameters in the gas phase and solution suggest that the complex formation reaction is spontaneous for [CfV/VIO2-L]1-/0 complexes and spontaneous at elevated temperatures (>298.15 K) for all other complexes. Spin-orbit corrections have a quantitative impact while the overall trend remains the same. Energy decomposition analysis (EDA) reveals that the interaction between actinyl and the ligand is mainly due to electrostatic contributions that decrease from Am to Cf along with an increase in orbital contributions due to the backdonation of charges from the actinyl metal center to the ligand that greatly stabilizes the Cf complex. The repulsive Pauli energy contribution is observed to increase in the case of [AnVO2-L]1- complexes from Am to Cf while a decrease is observed among [AnVIO2-L]0 complexes, showing minimum repulsion in [CfVIO2-L]0 complex formation. Overall, the hexavalent actinyl complexes show greater stability (increasing from Am to Cf) than their pentavalent counterparts.
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Affiliation(s)
- Abigail Jennifer G
- Department of Chemistry, SRM Institute of Science and Technology, Kattankulathur, Chennai 603203, Tamil Nadu, India.
| | - Yang Gao
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada. .,Institut National de La Recherche Scientifique (INRS)-Centre Énergie Matériaux Télécommunications, Varennes, QC, J3X 1P7, Canada.,Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, China
| | - Georg Schreckenbach
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada.
| | - Elumalai Varathan
- Department of Chemistry, SRM Institute of Science and Technology, Kattankulathur, Chennai 603203, Tamil Nadu, India.
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Yu X, Einkauf JD, Bryantsev VS, Cheshire MC, Reinhart BJ, Autschbach J, Burns JD. Spectroscopic characterization of neptunium(VI), plutonium(VI), americium(VI) and neptunium(V) encapsulated in uranyl nitrate hexahydrate. Phys Chem Chem Phys 2021; 23:13228-13241. [PMID: 34086024 DOI: 10.1039/d1cp01047f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The coordination of crystalline products resulting from the co-crystallization of Np(vi), Pu(vi), Am(vi), and Np(v) with uranyl nitrate hexahydrate (UNH) has been revealed through solid-state spectroscopic characterization via diffuse reflectance UV-Vis-NIR spectroscopy, SEM-EDS, and extended X-ray absorption fine structure (EXAFS) spectroscopy. Density functional and multireference wavefunction calculations were performed to analyze the An(vi/v)O2(NO3)2·2H2O electronic structures and to help assign the observed transitions in the absorption spectra. EXAFS show a similar coordination between the U(VI) in UNH and Np(vi) and Pu(vi); while Am resulted in a similar coordination to Am(iii), as reduction of Am(vi) occurred prior to EXAFS data being obtained. The co-crystallization of the oxidized transuranic species-penta- and hexavalent-with UNH, represents a significant advance from not only a practical standpoint in providing an elegant solution for used nuclear fuel recycle, but also as an avenue to expand the fundamental understanding of the 5f electronic behavior in the solid-state.
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Affiliation(s)
- Xiaojuan Yu
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260, USA.
| | - Jeffrey D Einkauf
- Chemical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Vyacheslav S Bryantsev
- Chemical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Michael C Cheshire
- Chemical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | | | - Jochen Autschbach
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260, USA.
| | - Jonathan D Burns
- Nuclear Engineering and Science Center, Texas A&M University, College Station, TX 77843, USA.
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Pérez-Conesa S, Martínez JM, Pappalardo RR, Marcos ES. Combining EXAFS and Computer Simulations to Refine the Structural Description of Actinyls in Water. Molecules 2020; 25:E5250. [PMID: 33187172 PMCID: PMC7697702 DOI: 10.3390/molecules25225250] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 11/05/2020] [Accepted: 11/08/2020] [Indexed: 11/16/2022] Open
Abstract
EXAFS spectroscopy is one of the most used techniques to solve the structure of actinoid solutions. In this work a systematic analysis of the EXAFS spectra of four actinyl cations, [UO2]2+, [NpO2]2+, [NpO2]+ and [PuO2]2+ has been carried out by comparing experimental results with theoretical spectra. These were obtained by averaging individual contributions from snapshots taken from classical Molecular Dynamics simulations which employed a recently developed [AnO2]2+/+ -H2O force field based on the hydrated ion model using a quantum-mechanical (B3LYP) potential energy surface. Analysis of the complex EXAFS signal shows that both An-Oyl and An-OW single scattering paths as well as multiple scattering ones involving [AnO2]+/2+ molecular cation and first-shell water molecules are mixed up all together to produce a very complex signal. Simulated EXAFS from the B3LYP force field are in reasonable agreement for some of the cases studied, although the k= 6-8 Å-1 region is hard to be reproduced theoretically. Except uranyl, all studied actinyls are open-shell electron configurations, therefore it has been investigated how simulated EXAFS spectra are affected by minute changes of An-O bond distances produced by the inclusion of static and dynamic electron correlation in the quantum mechanical calculations. A [NpO2]+-H2O force field based on a NEVPT2 potential energy surface has been developed. The small structural changes incorporated by the electron correlation on the actinyl aqua ion geometry, typically smaller than 0.07 Å, leads to improve the simulated spectrum with respect to that obtained from the B3LYP force field. For the other open-shell actinyls, [NpO2]2+ and [PuO2]2+, a simplified strategy has been adopted to improve the simulated EXAFS spectrum. It is computed taking as reference structure the NEVPT2 optimized geometry and including the DW factors of their corresponding MD simulations employing the B3LYP force field. A better agreement between the experimental and the simulated EXAFS spectra is found, confirming the a priori guess that the inclusion of dynamic and static correlation refine the structural description of the open-shell actinyl aqua ions.
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Affiliation(s)
| | | | | | - Enrique Sánchez Marcos
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain; (S.P.-C.); (J.M.M.); (R.R.P.)
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Pérez-Conesa S, Torrico F, Martínez JM, Pappalardo RR, Marcos ES. A general study of actinyl hydration by molecular dynamics simulations usingab initioforce fields. J Chem Phys 2019; 150:104504. [DOI: 10.1063/1.5083216] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Sergio Pérez-Conesa
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain
| | - Francisco Torrico
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain
| | - José M. Martínez
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain
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Oxidation and extraction of Am(VI) using a monoamidic extractant in 3D printed centrifugal contactors. J Radioanal Nucl Chem 2018. [DOI: 10.1007/s10967-018-6126-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Pérez-Conesa S, Martínez JM, Pappalardo RR, Sánchez Marcos E. Extracting the Americyl Hydration from an Americium Cationic Mixture in Solution: A Combined X-ray Absorption Spectroscopy and Molecular Dynamics Study. Inorg Chem 2018; 57:8089-8097. [DOI: 10.1021/acs.inorgchem.8b00164] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sergio Pérez-Conesa
- Department of Physical Chemistry, University of Seville, 41012 Seville, Spain
| | - José M. Martínez
- Department of Physical Chemistry, University of Seville, 41012 Seville, Spain
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