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Srivastava A, Ali SM, Dumpala RMR, Kumar S, Kumar P, Rawat N, Mohapatra PK. Unusual redox stability of pentavalent uranium with hetero-bifunctional phosphonocarboxylate: insight into aqueous speciation. Dalton Trans 2024; 53:7321-7339. [PMID: 38591248 DOI: 10.1039/d4dt00173g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/10/2024]
Abstract
The +5 state is an unusual oxidation state of uranium due to its instability in the aqueous phase. As a result, gaining information about its aqueous speciation is extremely difficult. The present work is an attempt in that direction and it provides insight into the existence of a new pentavalent species in the presence of hetero-bifunctional phosphonocarboxylate (PC) chelators, other than the carbonate ion, in the aqueous medium. The aqueous chemistry of pentavalent uranium species with three environmentally relevant PCs was probed using electrochemical and DFT methods to understand the redox energy and kinetics of conversion of the U(VI)/U(V) couple, stability, structure, stoichiometry, binding modes, etc. Interestingly, pentavalent uranium complexes with PCs are quite persistent over a wide range of pH starting from acidic to alkaline conditions. The PC chelators block the cation-cation interaction (CCI) of U(V) through strong hetero-bidentate chelation and intermolecular hydrogen bonding (IMHB) interactions which stabilize the pentavalent metal ion against disproportionation. For uranyl species in the presence of PCs, acting as chelators, CV plots were obtained at varying pH values from 2 to 8. The obtained results indicate an irreversible single redox peak involving U(VI) to U(V) conversion and association of a coupled chemical reaction with the electron transfer step. ESI-MS studies were performed to understand the speciation effect on the U(VI)/U(V) redox couple with varying pH. Speciation modelling of U(V) with the PC ligands was carried out, which indicated that the U(V) is redox stable in nearly 47% of the pH region in the presence of the PCs as compared to the carboxylate-based chelators. The free energy and reduction potential of the U(V) complexes and the reduction free energy and disproportionation free energy for the U(VI)/U(V) couple were determined by DFT computations in the presence of the PCs. In situ spectroelectrochemical spectra were recorded to provide evidence for the existence of U(V) species with PCs in the aqueous medium and to acquire its absorption spectra. The present study is highly significant for understanding the coordination chemistry of pentavalent uranium species, accurate modelling of uranium, and isolation of U(V).
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Affiliation(s)
- Ashutosh Srivastava
- Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai, India-400085.
| | - Sk Musharaf Ali
- Chemical Engineering Division, Bhabha Atomic Research Centre, Mumbai, India-400085
| | | | - Sumit Kumar
- Radioanalytical Chemistry Division, Bhabha Atomic Research Centre, Mumbai, India-400085
| | - Pranaw Kumar
- Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai, India-400085
| | - Neetika Rawat
- Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai, India-400085.
| | - P K Mohapatra
- Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai, India-400085.
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Verma PK, Mahanty B, Bhattacharyya A, Matveev PI, Borisova NE, Kalmykov SN, Mohapatra PK. Pyridine Diphosphonate Ligand for Stabilization of Tetravalent Uranium and Neptunium in Aqueous Medium under Aerobic Conditions. Inorg Chem 2024; 63:3348-3358. [PMID: 38320960 DOI: 10.1021/acs.inorgchem.3c03840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2024]
Abstract
Though uranium is usually present in its +6 oxidation state (as uranyl ion) in aqueous solutions, its conversion to oxidation states such as +4 or +5 is a challenging task. Electrochemical reduction and axial oxo activation are the preferred methods to get stable unusual oxidation states of uranium in an aqueous medium. In previous studies, dicarboxylic acid has been used to stabilize UO2+ in aqueous alkaline solutions. In the present work, a diphosphonate ligand was chosen due to its higher complexing ability compared to that of the carboxylate ligands. Neptunium complexation studies with 2,6-pyridinediphosphonic acid (PyPOH) indicated the formation of different species at different pH values and the complexation facilitates disproportionation of NpO2+ to Np4+ and NpO22+ at pH 2. Hexavalent actinides form insoluble complexes in aqueous media at pH = 2, as confirmed by UO22+ complexation studies. The in situ complexation-driven precipitation resulted in conversion to pure Np4+ in aqueous media as the Np4+-PyPOH complex. A strong complexing ability of the PyPOH ligand toward the Np4+ ion is also seen for the stabilization of the electrochemically generated U4+ in aqueous medium under aerobic conditions. The U4+-PyPOH complex was found to be stable for 3 months. Raman, UV-vis, fluorescence, and cyclic voltametric studies along with density functional theory (DFT) calculations were done to get structural insights into the PyPOH complexes of actinides in different oxidation states.
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Affiliation(s)
- Parveen Kumar Verma
- Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Bholanath Mahanty
- Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Arunasis Bhattacharyya
- Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Petr I Matveev
- Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1, Moscow 119991, Russia
| | - Nataliya E Borisova
- Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1, Moscow 119991, Russia
| | - Stepan N Kalmykov
- Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1, Moscow 119991, Russia
| | - Prasanta Kumar Mohapatra
- Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
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Molinas M, Meibom KL, Faizova R, Mazzanti M, Bernier-Latmani R. Mechanism of Reduction of Aqueous U(V)-dpaea and Solid-Phase U(VI)-dpaea Complexes: The Role of Multiheme c-Type Cytochromes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:7537-7546. [PMID: 37133831 DOI: 10.1021/acs.est.3c00666] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The biological reduction of soluble U(VI) complexes to form immobile U(IV) species has been proposed to remediate contaminated sites. It is well established that multiheme c-type cytochromes (MHCs) are key mediators of electron transfer to aqueous phase U(VI) complexes for bacteria such as Shewanella oneidensis MR-1. Recent studies have confirmed that the reduction proceeds via a first electron transfer forming pentavalent U(V) species that readily disproportionate. However, in the presence of the stabilizing aminocarboxylate ligand, dpaea2- (dpaeaH2═bis(pyridyl-6-methyl-2-carboxylate)-ethylamine), biologically produced U(V) persisted in aqueous solution at pH 7. We aim to pinpoint the role of MHC in the reduction of U(V)-dpaea and to establish the mechanism of solid-phase U(VI)-dpaea reduction. To that end, we investigated U-dpaea reduction by two deletion mutants of S. oneidensis MR-1-one lacking outer membrane MHCs and the other lacking all outer membrane MHCs and a transmembrane MHC-and by the purified outer membrane MHC, MtrC. Our results suggest that solid-phase U(VI)-dpaea is reduced primarily by outer membrane MHCs. Additionally, MtrC can directly transfer electrons to U(V)-dpaea to form U(IV) species but is not strictly necessary, underscoring the primary involvement of outer membrane MHCs in the reduction of this pentavalent U species but not excluding that of periplasmic MHCs.
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Affiliation(s)
- Margaux Molinas
- Environmental Microbiology Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
| | - Karin Lederballe Meibom
- Environmental Microbiology Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
| | - Radmila Faizova
- Group of Coordination Chemistry, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
| | - Marinella Mazzanti
- Group of Coordination Chemistry, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
| | - Rizlan Bernier-Latmani
- Environmental Microbiology Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
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Srivastava A, Dumpala RMR, Kumar P, Kumar R, Rawat N. Chemical and Redox Speciation of Uranyl with Three Environmentally Relevant Bifunctional Chelates: Multi-Technique Approach Combined with Theoretical Estimations. Inorg Chem 2022; 61:15452-15462. [PMID: 36123167 DOI: 10.1021/acs.inorgchem.2c01991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Carbon and phosphorous are two primary elements common to the bio-geosphere and are omnipresent in both biotic and abiotic arenas. Phosphonate and carboxylate are considered as building blocks of glyphosate and humic substances and constituents of the cellular wall of bacteria and are the driving functionalities for most of the chemical interactions involving these two elements. Phosphonocarboxylates, a combination of both the functionalities in one moiety, are ideal models to dig deep into for understanding the chemical interactions of the two functional groups with metal ions. Phosphorous and carbon majorly exist as inorganic/organic phosphate and carboxylate, respectively, in the bio-geosphere. Aquatic contamination is a major concern for uranium, and the presence of complexing agents would alter the uranium concentrations in aquifers. Determination of solution thermodynamic parameters, speciation plots, redox patterns, Eh-pH diagrams, coordination structures, and molecular-level understanding by density functional theory calculations was carried out to interpret the uranyl (UO22+) interaction with three environmentally relevant phosphonocarboxylates, namely, phosphono-formic acid (PFA), phosphono-acetic acid (PAA), and phosphono-propanoic acid (PPA). UO22+ forms 1:1 complexes with the three phosphonocarboxylates in the monoprotonated form, having nearly the same stability, and the complexes [UO2(PFAH)], [UO2(PAAH)], and [UO2(PPAH)] involve chelate formation of five, six, and seven membered rings, respectively, through the participation of an oxygen each from the carboxylate and phosphonate, strengthened by an intra-molecular hydrogen bonding through the proton of the phosphonate moiety with uranyl oxygen. The complex formations are favored both enthalpically and entropically, with the latter being more contributive to the overall free energy of formation. The redox speciation showed an aqueous soluble complex formation over a wide pH range of 1-8. Electrospray ionization mass spectrometry and extended X-ray absorption fine structure established the coordination modes, which are further corroborated by density functional calculations. The knowledge gained from the present studies provide potential inputs in framing the cleanup, sequestering, microbial, and bio-remediation strategies for uranyl from aquatic environments.
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Affiliation(s)
- Ashutosh Srivastava
- Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Rama Mohana Rao Dumpala
- Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.,Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology, P.O. Box 3640, Karlsruhe 76021, Germany
| | - Pranaw Kumar
- Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Ravi Kumar
- Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Neetika Rawat
- Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
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Patil SM, Rao Dumpala RM, Goswami D, Dawar R, Gupta R. Mechanistic Approach to Reveal Interaction of Uranyl Ions in Alkyltriphenylphosphonium Bromide-Based Deep Eutectic Solvent. Inorg Chem 2022; 61:12599-12609. [PMID: 35916667 DOI: 10.1021/acs.inorgchem.2c01547] [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
Speciation is known to control fundamental aspects of metal processing and electrochemical behavior such as solubility and redox potentials. Deep eutectic solvents (DESs) are an emerging class of green, low-cost and designer solvents and are being explored as alternatives for recycling nuclear fuel and critical materials. However, there is a lack of knowledge about the behavior of metals in them. Here, for the first time, we synthesized three new DESs based on alkyltriphenylphosphonium bromide (CnPPh3Br), with varied alkyl chain lengths (n), as the hydrogen-bond acceptor along with decanoic acid (DA) as the hydrogen-bond donor and explored the redox speciation of uranyl nitrate. The changes in the Fourier transform infrared and NMR spectra helped elucidate the formation of hydrogen bonds in DES. The absorption maxima of uranyl in DES was red-shifted by 10 nm compared to the free uranyl, with concomitant increase in intensity and luminescence lifetime, which suggested a strong interaction of uranyl nitrate with DES. Cyclic voltammetry was probed to understand the redox thermodynamics, transport properties, and heterogeneous electron transfer kinetics of the irreversible electron transfer of uranyl ions in the three DESs. Electrochemical and spectroscopic techniques together with density functional theory calculations unlocked microscopic insights into the solvation and speciation of UO22+ ions in three DESs and also the associated unusual trends observed in the physical properties of the DESs. The hydrogen-bonded structure of DES plays a crucial role in the redox behavior of the UO22+ ion due to its strong potent complexation with its components. The basic findings of the present work can have far-reaching consequences for the extraction, electrochemical separation, and future development of redox-based separation processes in the nuclear fuel cycle.
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Affiliation(s)
- Sushil M Patil
- Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.,Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094, India
| | - Rama Mohana Rao Dumpala
- Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.,Institute for Nuclear Waste Disposal (INE), Karlsruhe Institute of Technology (KIT), Karlsruhe 76131, Germany
| | - Dibakar Goswami
- Bio Organic Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.,Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094, India
| | - Rimpi Dawar
- Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Ruma Gupta
- Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.,Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094, India
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Arumugam K, Burton NA. Disproportionation of the Uranyl(V) Coordination Complexes in Aqueous Solution through Outer-Sphere Electron Transfer. Inorg Chem 2021; 60:18832-18842. [PMID: 34847326 DOI: 10.1021/acs.inorgchem.1c02575] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Among the linear actinyl(VI/V) cations, the uranyl(V) species are particularly intriguing because they are unstable and exhibit a unique behavior to undergo H+ promoted disproportionation in aqueous solution and form stable uranyl(VI) and U(IV) complexes. This study uses density functional theory (DFT) combined with the conductor-like polarizable continuum model approach to investigate [UO2]2+/+ to [UIVO2] reduction free energies (RFEs) and explores the stability of uranyl(V) complexes in aqueous solution through computing disproportionation free energies (DFEs) for an outer-sphere electron transfer process. In addition to the aqua complex (U1), another three commonly encountered ligands such as chloride (U2), acetate (U3), and carbonate (U4) in aqueous environmental conditions are taken into account. For the U1 complex, the computed 1e- (V/IV) and 2e- (VI/IV) RFEs are in good agreement with experiments. The computed DFEs reveal that the presence of H+ is imperative for the disproportionation to take place. Although the presence of the alkali cations favors the disproportionation to some extent, they cannot fully make the reaction thermodynamically feasible. For the anionic complexes, the high negative charge does not allow for the formation of a cation-cation encounter complex due to Coulombic repulsion. Furthermore, an additional factor is the ligand exchange reaction which is also an energy-demanding step. Therefore, the current study examined the Kern-Orlemann mechanism and our results validate the mechanism based on DFT computed DFEs and propose that for the anionic complexes, an outer-sphere electron transfer is highly probable and our computed protonation free energies further support this claim.
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Affiliation(s)
- Krishnamoorthy Arumugam
- Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Neil A Burton
- Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
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7
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An updated status and trends in actinide metal-organic frameworks (An-MOFs): From synthesis to application. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.214011] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Ortu F, Randall S, Moulding DJ, Woodward AW, Kerridge A, Meyer K, La Pierre HS, Natrajan LS. Photoluminescence of Pentavalent Uranyl Amide Complexes. J Am Chem Soc 2021; 143:13184-13194. [PMID: 34387466 PMCID: PMC8397311 DOI: 10.1021/jacs.1c05184] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Pentavalent uranyl species are crucial intermediates in transformations that play a key role for the nuclear industry and have recently been demonstrated to persist in reducing biotic and abiotic aqueous environments. However, due to the inherent instability of pentavalent uranyl, little is known about its electronic structure. Herein, we report the synthesis and characterization of a series of monomeric and dimeric, pentavalent uranyl amide complexes. These synthetic efforts enable the acquisition of emission spectra of well-defined pentavalent uranyl complexes using photoluminescence techniques, which establish a unique signature to characterize its electronic structure and, potentially, its role in biological and engineered environments via emission spectroscopy.
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Affiliation(s)
- Fabrizio Ortu
- Centre for Radiochemistry Resesarch, Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.,School of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, U.K
| | - Simon Randall
- Centre for Radiochemistry Resesarch, Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - David J Moulding
- Centre for Radiochemistry Resesarch, Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Adam W Woodward
- Centre for Radiochemistry Resesarch, Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.,Photon Science Institute, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Andrew Kerridge
- Department of Chemistry, Lancaster University, Lancaster LA1 4YB, U.K
| | - Karsten Meyer
- Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Department of Chemistry and Pharmacy, Inorganic Chemistry, Egerlandstr. 1, 91058 Erlangen, Germany
| | - Henry S La Pierre
- Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Department of Chemistry and Pharmacy, Inorganic Chemistry, Egerlandstr. 1, 91058 Erlangen, Germany.,School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States.,Nuclear and Radiological Engineering and Medical Physics Program, School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Louise S Natrajan
- Centre for Radiochemistry Resesarch, Department of Chemistry, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.,Photon Science Institute, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
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Fizer O, Fizer M, Sidey V. Quantum chemical insight on the uranyl benzoates association with cetylpyridinium. J Radioanal Nucl Chem 2021. [DOI: 10.1007/s10967-021-07843-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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