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Zhutova N, Réal F, Vallet V, Maurice R. Geometries, interaction energies and bonding in [Po(H 2O) n] 4+ and [PoCl n] 4-n complexes. Phys Chem Chem Phys 2022; 24:26180-26189. [PMID: 36278789 DOI: 10.1039/d2cp04001h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Polonium (Z = 84) is one of the rarest elements on Earth. More than a century after its discovery, its chemistry remains poorly known and even basic questions have not yet been satisfactorily addressed. In this work, we perform a systematic study of the geometries, interactions energies and bonding in basic polonium(IV) species, namely the hydrated [Po(H2O)n]4+ and chlorinated [PoCln]4-n complexes by means of gas-phase electronic structure calculations. We show that while up to nine water molecules can fit in the first coordination sphere of the polonium(IV) ion, its coordination sphere can already be filled with eight chloride ligands. Capitalising on previous theoretical studies, a focused methodological study based on interaction energies and bond distances allows us to validate the MP2/def2-TZVP level of theory for future ground-state studies. After discussing the similarities and differences between complexes with the same number of ligands, we perform topological analyses of the MP2 electron densities in the quantum theory of atoms in molecules (QTAIM) fashion. While the water complexes display typical signatures of closed-shell interactions, we reveal large Po-Cl delocalisation indices, especially in the hypothetical [PoCl]3+ complex. This "enhanced" covalency opens the way for a significant spin-orbit coupling (SOC) effect on the corresponding bond distance, which has been studied using two independent approaches (i.e. one a priori and one a posteriori). We finally conclude by stressing that while the SOC may not affect much the geometries of high-coordinated polonium(IV) complexes, it should definitely not be neglected in the case of low-coordinated ones.
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Affiliation(s)
- Nadiya Zhutova
- Subatech, UMR CNRS 6457, IN2P3/IMT Atlantique/Université de Nantes, 4 rue A. Kastler, 44307, Nantes Cedex 3, France
- Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, F-35000, Rennes, France.
| | - Florent Réal
- Univ. Lille, CNRS, UMR 8523-PhLAM-Physique des Lasers, Atomes et Molécules, F-59000, Lille, France.
| | - Valérie Vallet
- Univ. Lille, CNRS, UMR 8523-PhLAM-Physique des Lasers, Atomes et Molécules, F-59000, Lille, France.
| | - Rémi Maurice
- Subatech, UMR CNRS 6457, IN2P3/IMT Atlantique/Université de Nantes, 4 rue A. Kastler, 44307, Nantes Cedex 3, France
- Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, F-35000, Rennes, France.
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Separation, speciation, and mechanism of astatine and bismuth extraction from nitric acid into 1-octanol and methyl anthranilate. Sep Purif Technol 2022. [DOI: 10.1016/j.seppur.2021.120088] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Liu L, Rahali S, Maurice R, Gomez Pech C, Montavon G, Le Questel JY, Graton J, Champion J, Galland N. An expanded halogen bonding scale using astatine. Chem Sci 2021; 12:10855-10861. [PMID: 34447565 PMCID: PMC8372311 DOI: 10.1039/d1sc02133h] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 07/12/2021] [Indexed: 01/07/2023] Open
Abstract
As a non-covalent interaction, halogen bonding is now acknowledged to be useful in all fields where the control of intermolecular recognition plays a pivotal role. Halogen-bond basicity scales allow quantification of the halogen bonding of referential donors with organic functional groups from a thermodynamic point of view. Herein we present the pK BAtI basicity scale to provide the community an overview of halogen-bond acceptor strength towards astatine, the most potent halogen-bond donor element. This experimental scale is erected on the basis of complexation constants measured between astatine monoiodide (AtI) and sixteen selected Lewis bases. It spans over 6 log units and culminates with a value of 5.69 ± 0.32 for N,N,N',N'-tetramethylthiourea. On this scale, the carbon π-bases are the weakest acceptors, the oxygen derivatives cover almost two-thirds of the scale, and sulphur bases exhibit the highest AtI basicity. Regarding the applications of 211At in targeted radionuclide therapy, stronger labelling of carrier agents could be envisaged on the basis of the pK BAtI scale.
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Affiliation(s)
- Lu Liu
- SUBATECH UMR 6457, CNRS, IMT Atlantique, Université de Nantes 4 Rue Alfred Kastler 44307 Nantes France
| | - Seyfeddine Rahali
- Université de Nantes, CNRS, CEISAM UMR 6230 44000 Nantes France
- Department of Chemistry, College of Science and Arts, Qassim University Ar Rass Saudi Arabia
| | - Rémi Maurice
- SUBATECH UMR 6457, CNRS, IMT Atlantique, Université de Nantes 4 Rue Alfred Kastler 44307 Nantes France
| | - Cecilia Gomez Pech
- SUBATECH UMR 6457, CNRS, IMT Atlantique, Université de Nantes 4 Rue Alfred Kastler 44307 Nantes France
- Université de Nantes, CNRS, CEISAM UMR 6230 44000 Nantes France
| | - Gilles Montavon
- SUBATECH UMR 6457, CNRS, IMT Atlantique, Université de Nantes 4 Rue Alfred Kastler 44307 Nantes France
| | | | - Jérôme Graton
- Université de Nantes, CNRS, CEISAM UMR 6230 44000 Nantes France
| | - Julie Champion
- SUBATECH UMR 6457, CNRS, IMT Atlantique, Université de Nantes 4 Rue Alfred Kastler 44307 Nantes France
| | - Nicolas Galland
- Université de Nantes, CNRS, CEISAM UMR 6230 44000 Nantes France
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Guérard F, Maingueneau C, Liu L, Eychenne R, Gestin JF, Montavon G, Galland N. Advances in the Chemistry of Astatine and Implications for the Development of Radiopharmaceuticals. Acc Chem Res 2021; 54:3264-3275. [PMID: 34350753 DOI: 10.1021/acs.accounts.1c00327] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
ConspectusAstatine (At) is the rarest on Earth of all naturally occurring elements, situated below iodine in the periodic table. While only short-lived isotopes (t1/2 ≤ 8.1 h) are known, 211At is the object of growing attention due to its emission of high-energy alpha particles. Such radiation is highly efficient to eradicate disseminated tumors, provided that the radionuclide is attached to a cancer-targeting molecule. The interest in applications of 211At in nuclear medicine translates into the increasing number of cyclotrons able to produce it. Yet, many challenges related to the minute amounts of available astatine are to be overcome in order to characterize its physical and chemical properties. This point is of paramount importance to develop synthetic strategies and solve the labeling instability in current approaches that limits the use of 211At-labeled radiopharmaceuticals. Despite its discovery in the 1940s, only the past decade has seen a significant rise in the understanding of astatine's basic chemical and radiochemical properties, thanks to the development of new analytical and computational tools.In this Account, we give a concise summary of recent advances in the determination of the physicochemical properties of astatine, putting in perspective the duality of this element which exhibits the characteristics both of a halogen and of a metal. Striking features were evidenced in the recent determination of its Pourbaix diagram such as the identification of stable cationic species, At+ and AtO+, contrasting with other halogens. Like metals, these species were shown to form complexes with anionic ligands and to exhibit a particular affinity for organic species bearing soft donor atoms. On the other hand, astatine shares many characteristics with other halogen elements. For instance, the At- species exists in water, but with the least range of EH-pH stability in the halogen series. Astatine can form molecular interactions through halogen bonding, and it was only recently identified as the strongest halogen-bond donor. This ability is nonetheless affected by relativistic effects, which translate to other peculiarities for this heavy element. For instance, the spin-orbit coupling boosts astatine's propensity to form charge-shift bonds, catching up with the behavior of the lightest halogens (fluorine, chlorine).All these new data have an impact on the development of radiolabeling strategies to turn 211At into radiopharmaceuticals. Inspired by the chemistry of iodine, the chemical approaches have sparsely evolved over the past decades and have long been limited to electrophilic halodemetalation reactions to form astatoaryl compounds. Conversely, recent developments have favored the use of the more stable At- species including the aromatic nucleophilic substitution with diaryliodonium salts or the copper-catalyzed halodeboronation of arylboron precursors. However, it is clear that new bonding modalities are necessary to improve the in vivo stability of 211At-labeled aryl compounds. The tools and data gathered over the past decade will contribute to instigate original strategies for overcoming the challenges offered by this enigmatic element. Alternatives to the C-At bond such as the B-At and the metal-At bonds are typical examples of exciting new axes of research.
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Affiliation(s)
- François Guérard
- Université de Nantes, CNRS, Inserm, CRCINA, F-44000 Nantes, France
| | | | - Lu Liu
- IMT-Atlantique Bretagne-Pays de la Loire - Nantes Campus, SUBATECH, UMR CNRS 6457, F-44000 Nantes, France
| | - Romain Eychenne
- Université de Nantes, CNRS, Inserm, CRCINA, F-44000 Nantes, France
- Arronax GIP, F-44817 Saint-Herblain, France
| | | | - Gilles Montavon
- IMT-Atlantique Bretagne-Pays de la Loire - Nantes Campus, SUBATECH, UMR CNRS 6457, F-44000 Nantes, France
| | - Nicolas Galland
- Université de Nantes, CNRS, CEISAM UMR 6230, F-44000 Nantes, France
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Astatine Facing Janus: Halogen Bonding vs. Charge-Shift Bonding. Molecules 2021; 26:molecules26154568. [PMID: 34361716 PMCID: PMC8347445 DOI: 10.3390/molecules26154568] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/21/2021] [Accepted: 07/23/2021] [Indexed: 12/04/2022] Open
Abstract
The nature of halogen-bond interactions was scrutinized from the perspective of astatine, potentially the strongest halogen-bond donor atom. In addition to its remarkable electronic properties (e.g., its higher aromaticity compared to benzene), C6At6 can be involved as a halogen-bond donor and acceptor. Two-component relativistic calculations and quantum chemical topology analyses were performed on C6At6 and its complexes as well as on their iodinated analogues for comparative purposes. The relativistic spin–orbit interaction was used as a tool to disclose the bonding patterns and the mechanisms that contribute to halogen-bond interactions. Despite the stronger polarizability of astatine, halogen bonds formed by C6At6 can be comparable or weaker than those of C6I6. This unexpected finding comes from the charge-shift bonding character of the C–At bonds. Because charge-shift bonding is connected to the Pauli repulsion between the bonding σ electrons and the σ lone-pair of astatine, it weakens the astatine electrophilicity at its σ-hole (reducing the charge transfer contribution to halogen bonding). These two antinomic characters, charge-shift bonding and halogen bonding, can result in weaker At-mediated interactions than their iodinated counterparts.
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Vasiliu M, Peterson KA, Dixon DA. Bond Dissociation Energies in Heavy Element Chalcogen and Halogen Small Molecules. J Phys Chem A 2021; 125:1892-1902. [PMID: 33645983 DOI: 10.1021/acs.jpca.0c11393] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Thermodynamic properties including bond dissociation energies (BDEs), heats of formation, and gas-phase acidities for the hydrides and dimers of chalcogens and halogens, H2Y, HX, Y2, and X2 for Y = Se, Te, and At and X = Br, I, and At, have been predicted using the Feller-Peterson-Dixon composite-correlated molecular orbital theory approach. A full four-component CCSD(T) approach was used to calculate the spin-orbit effects on thermodynamic properties, except for Se2, where the AoC-DHF value was used due to strong multireference effects in Se2 for the SO calculations. The calculated results show that the At2 BDE is quite small, 19.5 kcal/mol, with much of the low bond energy due to spin-orbit effects. H2Po is not predicted to be stable to dehydrogenation to Po + H2 in terms of the free energy at 298 K. In the gas phase, HAt is predicted to be a stronger acid than H2SO4. The current results provide insights into potential difficulties in the actual experimental observation of such species for heavy elements.
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Affiliation(s)
- Monica Vasiliu
- Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35401, United States
| | - Kirk A Peterson
- Department of Chemistry, Washington State University, Pullman, Washington 99164, United States
| | - David A Dixon
- Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35401, United States
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Sarr S, Graton J, Rahali S, Montavon G, Galland N. Delocalized relativistic effects, from the viewpoint of halogen bonding. Phys Chem Chem Phys 2021; 23:4064-4074. [PMID: 33433548 DOI: 10.1039/d0cp05840h] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The ability of organic and inorganic compounds bearing both iodine and astatine atoms to form halogen-bond interactions is theoretically investigated. Upon inclusion of the relativistic spin-orbit interaction, the I-mediated halogen bonds are more affected than the At-mediated ones in many cases. This unusual outcome is disconnected from the behavior of iodine's electrons. The significant decrease of astatine electronegativity with the spin-orbit coupling triggers a redistribution of the electron density, which propagates relativistic effects toward the distant iodine atom. This mechanism can be controlled by introducing suitable substituents and, in particular, strengthened by taking advantage of electron-withdrawing inductive and mesomeric effects. Noticeable relativistic effects can actually be transferred to light atoms properties, e.g., the halogen-bond basicity of bridgehead carbon atoms doubled in propellane derivatives.
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Affiliation(s)
- Serigne Sarr
- Université de Nantes, CNRS, CEISAM UMR 6230, 44000 Nantes, France.
| | - Jérôme Graton
- Université de Nantes, CNRS, CEISAM UMR 6230, 44000 Nantes, France.
| | - Seyfeddine Rahali
- Department of Chemistry, College of Science and Arts, Qassim University, 51921 Ar Rass, Saudi Arabia
| | - Gilles Montavon
- IMT Atlantique, CNRS, SUBATECH UMR 6457, 44307 Nantes, France
| | - Nicolas Galland
- Université de Nantes, CNRS, CEISAM UMR 6230, 44000 Nantes, France.
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