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Jennifer G A, Gao Y, Schreckenbach G, Varathan E. Periodic Trends in the Stabilization of Actinyls in Their Higher Oxidation States Using Pyrrophen Ligands. Inorg Chem 2023; 62:6920-6933. [PMID: 37104857 DOI: 10.1021/acs.inorgchem.3c00022] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
Owing to the prominent existence and unique chemistry of actinyls, their complexation with suitable ligands is of significant interest. The complexation of high-valent actinyl moieties (An = U, Np, Pu and Am) with the acyclic sal-porphyrin analogue called "pyrrophen" (L(1)) and its dimethyl derivative (L(2)) with four nitrogen and two oxygen donor atoms was studied using relativistic density functional theory. Based on the periodic trends, the [UVO2-L(1)/L(2)]1- complexes show shorter bond lengths and higher bond orders that increase across the series of pentavalent actinyl complexes mainly due to the localization of the 5f orbitals. Among the hexavalent complexes, the [UVIO2-L(1)/L(2)] complexes have the shortest bonds. Following the uranyl complex, due to the plutonium turn, the [AmVIO2-L(1)/L(2)] complexes exhibit comparable properties with those of the former. Charge analysis suggests the complexation to be facilitated through ligand-to-metal charge transfer (LMCT) mainly through σ donation. Thermodynamic feasibility of complexation was modeled using hydrated actinyl moieties in aqueous medium and was found to be spontaneous. The dimethylated pyrrophen (L(2)) shows higher magnitudes of thermodynamic parameters indicating increased feasibility compared to the unsubstituted ligand (L(1)). Energy decomposition analysis (EDA) along with extended transition-state-natural orbitals for chemical valence theory (ETS-NOCV) analysis shows that the dominant electrostatic contributions decrease across the series and are counteracted by Pauli repulsion. Slight but considerable covalency is provided to hexavalent actinyl complexes by orbital contributions; this was confirmed by molecular orbital (MO) analysis that suggests strong covalency in americyl (VI) complexes. In addition to the pentavalent and hexavalent actinyl moieties, heptavalent actinyl species of neptunyl, plutonyl, and americyl were studied. Beyond the influence of the charges, the geometric and electronic properties point to the stabilization of neptunyl (VII) in the pyrrophen ligand environment, while the others shift to a lower (+VI) and relatively stable OS on complexation.
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Affiliation(s)
- Abigail Jennifer G
- Department of Chemistry, SRM Institute of Science and Technology, Kattankulathur 603203, Tamil Nadu, India
| | - Yang Gao
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, China
- NHC Key Laboratory of Nuclear Technology Medical Transformation (Mianyang Central Hospital), Mianyang 621010, 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 603203, Tamil Nadu, India
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Identification of uranium hexavalent compounds using X-ray photoelectron spectroscopy. J Radioanal Nucl Chem 2021. [DOI: 10.1007/s10967-021-08085-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Chattaraj S, Bhattacharyya A, Sadhu B. Role of O Substitution in Expanded Porphyrins on Uranyl Complexation: Orbital- and Density-Based Analyses. Inorg Chem 2021; 60:15351-15363. [PMID: 34586785 DOI: 10.1021/acs.inorgchem.1c01981] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Search for new U(VI) sequestering macrocyclic ligands is an important area of research due to manifold applications. Besides hard- or soft-donor-based ligands, mixed-donor ligands are also gaining popularity in achieving optimized performances. However, how the combination of hard-soft-donor centers alters the bonding interactions with U(VI) is still not well-understood. Moreover, a consensus is yet to be reached on the nature and role of underlying covalent interactions in mixed N,O-donor ligands. In this work, using the relativistic density functional theory (DFT), we attempted to address these intriguing issues by investigating the subtle change in bonding characteristics of the uranyl ion upon binding with an expanded porphyrin, viz. sapphyrin, with subsequent O substitutions at the cavity. The results obtained from a range of modern analysis tools suggest that in the O-substituted sapphyrin variants, UO22+ prefers to bind with N over O, and an increase in the number of O-donor sites at the cavity prompts UO22+ to have a better interaction with the rest of the N-donor-centers. Although O donors are involved in more numbers of mixed molecular orbitals, the variation in the amplitude of overlap and the better σ-donation ability favor N to have stronger bonding interactions with uranyl. Molecular orbital (MO) and density of states (DOS) analyses show favorable participation of U(d), and the involvement of U(f) orbitals in bonding is of a low extent but non-negligible. Although electrostatic interaction dominates at U-O/N bonds in the equatorial plane, the quantum theory of atoms in molecules descriptors, MO analysis, and overlap-integral calculations confirm the presence of underlying near-degeneracy-driven covalent interactions.
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Affiliation(s)
- Saparya Chattaraj
- Health Physics Division, Health Safety and Environment Group, Bhabha Atomic Research Center, Mumbai 400085, India.,Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Arunasis Bhattacharyya
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India.,Radiochemistry Division, Radiochemistry and Isotope Group, Bhabha Atomic Research Center, Mumbai 400085, India
| | - Biswajit Sadhu
- Health Physics Division, Health Safety and Environment Group, Bhabha Atomic Research Center, Mumbai 400085, India
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Varathan E, Gao Y, Schreckenbach G. Computational Study of Actinyl Ion Complexation with Dipyriamethyrin Macrocyclic Ligands. J Phys Chem A 2021; 125:920-932. [PMID: 33476158 DOI: 10.1021/acs.jpca.0c08760] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Relativistic density functional theory has been employed to characterize [AnO2(L)]0/-1 complexes, where An = U, Np, Pu, and Am, and L is the recently reported hexa-aza porphyrin analogue, termed dipyriamethyrin, which contains six nitrogen donor atoms (four pyrrolic and two pyridine rings). Shorter axial (An═O) and longer equatorial (An-N) bond lengths are observed when going from AnVI to AnV. The actinide to pyrrole nitrogen bonds are shorter as compared to the bonds to the pyridine nitrogens; the former also play a dominant role in the formation of the actinyl (VI and V) complexes. Natural population analysis shows that the pyrrole nitrogen atoms in all the complexes carry higher negative charges than the pyridine nitrogens. Upon binding actinyl ions with the ligand a significant ligand-to-metal charge transfer takes place in all the actinyl (VI and V) complexes. The formation energy of the actinyl(VI,V) complexes in the gas-phase is found to decrease in the order of UO2L > PuO2L > NpO2L > AmO2L. This trend is consistent with results for the formation of complexes in dichloromethane solution. The calculated ΔG and ΔH values are negative for all the complexes. Energy decomposition analysis (EDA) indicates that the interactions between actinyl(V/VI) and ligand are mainly controlled by electrostatic components over covalent orbital interactions, and the covalent character gradually decreases from U to Am for both pentavalent and hexavalent actinyl complexes.
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Affiliation(s)
- Elumalai Varathan
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada
| | - Yang Gao
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada
| | - Georg Schreckenbach
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada
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Apostolidis C, Kovács A, Walter O, Colineau E, Griveau J, Morgenstern A, Rebizant J, Caciuffo R, Panak PJ, Rabung T, Schimmelpfennig B, Perfetti M. Tris-{hydridotris(1-pyrazolyl)borato}actinide Complexes: Synthesis, Spectroscopy, Crystal Structure, Bonding Properties and Magnetic Behaviour. Chemistry 2020; 26:11293-11306. [PMID: 32519790 PMCID: PMC7497007 DOI: 10.1002/chem.202001095] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 05/26/2020] [Indexed: 01/10/2023]
Abstract
The isostructural compounds of the trivalent actinides uranium, neptunium, plutonium, americium, and curium with the hydridotris(1-pyrazolyl)borato (Tp) ligand An[η3 -HB(N2 C3 H3 )3 ]3 (AnTp3 ) have been obtained through several synthetic routes. Structural, spectroscopic (absorption, infrared, laser fluorescence) and magnetic characterisation of the compounds were performed in combination with crystal field, density functional theory (DFT) and relativistic multiconfigurational calculations. The covalent bonding interactions were analysed in terms of the natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) models.
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Affiliation(s)
| | - Attila Kovács
- European Commission, Joint Research CentrePostfach 234076125KarlsruheGermany
| | - Olaf Walter
- European Commission, Joint Research CentrePostfach 234076125KarlsruheGermany
| | - Eric Colineau
- European Commission, Joint Research CentrePostfach 234076125KarlsruheGermany
| | | | - Alfred Morgenstern
- European Commission, Joint Research CentrePostfach 234076125KarlsruheGermany
| | - Jean Rebizant
- European Commission, Joint Research CentrePostfach 234076125KarlsruheGermany
| | - Roberto Caciuffo
- European Commission, Joint Research CentrePostfach 234076125KarlsruheGermany
| | - Petra J. Panak
- Institut für Nukleare EntsorgungForschungszentrum KarlsruhePostfach 364076021KarlsruheGermany
| | - Thomas Rabung
- Institut für Nukleare EntsorgungForschungszentrum KarlsruhePostfach 364076021KarlsruheGermany
| | - Bernd Schimmelpfennig
- Institut für Nukleare EntsorgungForschungszentrum KarlsruhePostfach 364076021KarlsruheGermany
| | - Mauro Perfetti
- Department of ChemistryUniversity of CopenhagenUniversitetsparken 52100CopenhagenDenmark
- Department of Chemistry “Ugo Schiff” and INSTM Research UnitUniversity of FlorenceVia della Lastruccia 350019Sesto FiorentinoItaly
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Chandrasekar A, Ghanty TK, Brahmmananda Rao CVS, Sundararajan M, Sivaraman N. Strong influence of weak hydrogen bonding on actinide-phosphonate complexation: accurate predictions from DFT followed by experimental validation. Phys Chem Chem Phys 2019; 21:5566-5577. [PMID: 30785454 DOI: 10.1039/c9cp00479c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Among the varied classes of weak hydrogen bond, the CHO type is one of immense interest as it governs the finer structures of biological and chemical molecules, hence determining their functionalities. In the present work, this weak hydrogen bond has been shown to strongly influence the complexation behaviour of uranyl nitrate [UO2(NO3)2] with diamyl-H-phosphonate (DAHP) and its branched isomer disecamyl-H-phosphonate (DsAHP). The structures of the bare ligands and complexes have been optimized by density functional theory (DFT) calculations. Surprisingly, despite having the same chemical composition the branched UO2(NO3)2·2DsAHP complex shows a remarkably higher stability (by ∼14 kcal mol-1) compared to the UO2(NO3)2·2DAHP complex. Careful inspection of the optimized structures reveals the existence of multiple CHO hydrogen-bonding interactions between the nitrate oxygens or U[double bond, length as m-dash]O oxygens and the α-hydrogens in the alkyl chains of the ligands. Comparatively stronger such bonds are found in the UO2(NO3)2·2DsAHP complex. The binding free energies associated with the complexes are computed and favoured superior binding energetics for the more stable UO2(NO3)2·2DsAHP complex. Calculations involving diisoamyl-H-phosphonate (DiAHP) and its complexes have also been performed. Theoretical predictions are experimentally tested by carrying out the extraction of U(vi) from nitric acid media using these ligands. DAHP, DsAHP and DiAHP are synthesised, characterised by NMR and evaluated for their physicochemical properties viz. viscosity, density and aqueous solubility. It was experimentally discovered that indeed DsAHP complexation with uranyl nitrate is more favoured. H-phosphonates are generically classified as acidic extractants owing to the formation of an enol tautomer at lower acidities, hence complexing the metal ion by proton exchange. Our experiments interestingly reveal a neutral ligand characteristic for DsAHP alone which is generically an acidic extractant. Furthermore, the enol tautomer of H-phosphonates that governs their extraction profiles at low acidities is also explored by DFT and the anomalous pH dependent complexation trend of DsAHP could be successfully explained. The extractions of Pu(iv) and Th(iv) have also been carried out in addition to U(vi). Solvent extraction behaviour of Am(iii) was also studied with all three ligands; the positive binding energies computed for the Am(iii) complexation corroborate with our experimental results on the poor extraction of Am(iii).
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Affiliation(s)
- Aditi Chandrasekar
- Homi Bhabha National Institute, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu 603102, India.
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Comparative Study of Complexes of Rare Earths and Actinides with 2,6-Bis(1,2,4-triazin-3-yl)pyridine. INORGANICS 2019. [DOI: 10.3390/inorganics7030026] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Complexes of group III metals (rare earth and actinides) with 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (BTP) have been investigated by computational (DFT) and, in limited cases, by experimental (FT-IR, X-ray) techniques with the goal of determining the characteristics of metal–ligand interactions. The DFT calculations using the M062X exchange-correlation functional revealed that metal–ligand distances correlate with the ionic radii of the metals, in agreement with available X-ray diffraction results on the Sc, Y, La, U, and Pu complexes. A related blue-shift trend could be observed in seven characteristic bands in the IR spectra associated with metal–ligand vibrations. The computations uncovered considerable charge transfer interactions, particularly in the actinide complexes, as important covalent contributions to the metal–ligand bonding. The covalent character of the metal–ligand bonds decreases in the actinides, from U to Cm.
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Decomposition of d- and f-Shell Contributions to Uranium Bonding from the Quantum Theory of Atoms in Molecules: Application to Uranium and Uranyl Halides. INORGANICS 2018. [DOI: 10.3390/inorganics6030088] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The electronic structures of a series of uranium hexahalide and uranyl tetrahalide complexes were simulated at the density functional theoretical (DFT) level. The resulting electronic structures were analyzed using a novel application of the Quantum Theory of Atoms in Molecules (QTAIM) by exploiting the high symmetry of the complexes to determine 5f- and 6d-shell contributions to bonding via symmetry arguments. This analysis revealed fluoride ligation to result in strong bonds with a significant covalent character while ligation by chloride and bromide species resulted in more ionic interactions with little differentiation between the ligands. Fluoride ligands were also found to be most capable of perturbing an existing electronic structure. 5f contributions to overlap-driven covalency were found to be larger than 6d contributions for all interactions in all complexes studied while degeneracy-driven covalent contributions showed significantly greater variation. σ-contributions to degeneracy-driven covalency were found to be consistently larger than those of individual π-components while the total π-contribution was, in some cases, larger. Strong correlations were found between overlap-driven covalent bond contributions, U–O vibrational frequencies, and energetic stability, which indicates that overlap-driven covalency leads to bond stabilization in these complexes and that uranyl vibrational frequencies can be used to quantitatively probe equatorial bond covalency. For uranium hexahalides, degeneracy-driven covalency was found to anti-correlate with bond stability.
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Kovács A, Dau PD, Marçalo J, Gibson JK. Pentavalent Curium, Berkelium, and Californium in Nitrate Complexes: Extending Actinide Chemistry and Oxidation States. Inorg Chem 2018; 57:9453-9467. [PMID: 30040397 DOI: 10.1021/acs.inorgchem.8b01450] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pentavalent actinyl nitrate complexes AnVO2(NO3)2- were produced by elimination of two NO2 from AnIII(NO3)4- for An = Pu, Am, Cm, Bk, and Cf. Density functional theory (B3LYP) and relativistic multireference (CASPT2) calculations confirmed the AnO2(NO3)2- as AnVO2+ actinyl moieties coordinated by nitrates. Computations of alternative AnIIIO2(NO3)2- and AnIVO2(NO3)2- revealed significantly higher energies. Previous computations for bare AnO2+ indicated AnVO2+ for An = Pu, Am, Cf, and Bk, but CmIIIO2+: electron donation from nitrate ligands has here stabilized the first CmV complex, CmVO2(NO3)2-. Structural parameters and bonding analyses indicate increasing An-NO3 bond covalency from Pu to Cf, in accordance with principles for actinide separations. Atomic ionization energies effectively predict relative stabilities of oxidation states; more reliable energies are needed for the actinides.
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Affiliation(s)
- Attila Kovács
- European Commission, Joint Research Centre , P.O. Box 2340, 76125 Karlsruhe , Germany
| | - Phuong D Dau
- Chemical Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 United States
| | - Joaquim Marçalo
- Centro de Ciências e Tecnologias Nucleares & Centro de Química Estrutural , Instituto Superior Técnico, Universidade de Lisboa , 2695-066 Bobadela LRS , Portugal
| | - John K Gibson
- Chemical Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 United States
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Meng D, Pu N, Mei L, Sun T, Xu L, Shi W, Chen J, Xu C. Complexation of U(VI) with diphenyldithiophosphinic acid: spectroscopy, structure and DFT calculations. J Radioanal Nucl Chem 2018. [DOI: 10.1007/s10967-018-5844-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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