1
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Comas-Vilà G, Salvador P. Quantification of the Donor-Acceptor Character of Ligands by the Effective Fragment Orbitals. Chemphyschem 2024:e202400582. [PMID: 38831714 DOI: 10.1002/cphc.202400582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Accepted: 06/03/2024] [Indexed: 06/05/2024]
Abstract
Metal-ligand interactions are at the heart of transition metal complexes. The Dewar-Chat-Duncanson model is often invoked, whereby the metal-ligand bonding is decomposed into the simultaneous ligand→metal electron donation and the metal→ligand back-donation. The separate quantification of both effects is not a trivial task, neither from experimental nor computational exercises. In this work we present the effective fragment orbitals (EFOs) and their occupations as a general procedure beyond the Kohn-Sham density functional theory (KS-DFT) framework for the identification and quantification of donor-acceptor interactions, using solely the wavefunction of the complex. Using a common Fe(II) octahedral complex framework, we quantify the σ-donor, π-donor, and π-acceptor character for a large and chemically diverse set of ligands, by introducing the respective descriptors σd, πd, and πa. We also explore the effect of the metal size, coordination number, and spin state on the donor/acceptor features. The spin-state is shown to be the most critical effect, inducing a systematic decrease of the sigma donation and π-backdonation going from low spin to high spin. Finally, we illustrate the ability of the EFOs to rationalize the Tolman electronic parameter and the trans influence in planar square complexes in terms of these new descriptors.
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Affiliation(s)
- Gerard Comas-Vilà
- Departament de Química and Institut de Química Computacional i Catàlisi (IQCC), Universitat de Girona, Campus Montilivi s/n, 17071, Girona, Spain
| | - Pedro Salvador
- Departament de Química and Institut de Química Computacional i Catàlisi (IQCC), Universitat de Girona, Campus Montilivi s/n, 17071, Girona, Spain
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2
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Merschel A, Vishnevskiy YV, Neumann B, Stammler HG, Ghadwal RS. Boosting the π-Acceptor Property of Mesoionic Carbenes by Carbonylation with Carbon Monoxide. Angew Chem Int Ed Engl 2024; 63:e202318525. [PMID: 38284508 DOI: 10.1002/anie.202318525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 01/17/2024] [Accepted: 01/17/2024] [Indexed: 01/30/2024]
Abstract
We report the room temperature dimerization of carbon monoxide mediated by C4/C5-vicinal anionic dicarbenes Li(ADC) (ADC = ArC{(Dipp)NC}2 ; Dipp = 2,6-iPr2 C6 H3 ; Ar = Ph, DMP (4-Me2 NC6 H4 ), Bp (4-PhC6 H4 )) to yield (E)-ethene-1,2-bis(olate) (i.e. - O-C=C-O- = COen ) bridged mesoionic carbene (iMIC) lithium compounds COen -[(iMIC)Li]2 (COen -[iMIC]2 = [ArC{(Dipp)NC}2 (CO)]2 ) in quantitative yields. COen -[(iMIC)Li]2 are highly colored stable solids, exhibit a strikingly small HOMO-LUMO energy gap, and readily undergo 2e-oxidations with selenium, CuCl (or CuCl2 ), and AgCl to afford the dinuclear compounds COon -[(iMIC)E]2 (E = Se, CuCl, AgCl) featuring a 1,2-dione bridged neutral bis-iMIC (i.e. COon -[iMIC]2 = [ArC{(Dipp)NC}2 (C=O)]2 ). COen -[(iMIC)Li]2 undergo redox-neutral salt metathesis reactions with LiAlH4 and (Et2 O)2 BeBr2 and afford COen -[(iMIC)AlH2 ]2 and COen -[(iMIC)BeBr]2 , in which the dianionic COen -moiety remains intact. All compounds have been characterized by NMR spectroscopy, mass spectrometry, and X-ray diffraction. Stereoelectronic properties of COon -[iMIC]2 are quantified by experimental and theoretical methods.
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Affiliation(s)
- Arne Merschel
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Yury V Vishnevskiy
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Beate Neumann
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Hans-Georg Stammler
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Rajendra S Ghadwal
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
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3
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Scott JS, Schneider JE, Tewelde EG, Gardner JG, Anferov SW, Filatov AS, Anderson JS. Combining Donor Strength and Oxidative Stability in Scorpionates: A Strongly Donating Fluorinated Mesoionic Tris(imidazol-5-ylidene)borate Ligand. Inorg Chem 2023; 62:21224-21232. [PMID: 38051936 DOI: 10.1021/acs.inorgchem.3c03251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Strongly donating scorpionate ligands support the study of high-valent transition metal chemistry; however, their use is frequently limited by oxidative degradation. To address this concern, we report the synthesis of a tris(imidazol-5-ylidene)borate ligand featuring trifluoromethyl groups surrounding its coordination pocket. This ligand represents the first example of a chelating poly(imidazol-5-ylidene) mesoionic carbene ligand, a scaffold that is expected to be extremely donating. The {NiNO}10 complex of this ligand, as well as that of a previously reported strongly donating tris(imidazol-2-ylidene)borate, has been synthesized and characterized. This new ligand's strong donor properties, as measured by the υNO of its {NiNO}10 complex and natural bonding orbital second-order perturbative energy analysis, are at par with those of the well-studied alkyl-substituted tris(imidazol-2-ylidene)borates, which are known to effectively stabilize high-valent intermediates. The good donor properties of this ligand, despite the electron-withdrawing trifluoromethyl substituents, arise from the strongly donating imidazol-5-ylidene mesoionic carbene arms. These donor properties, when combined with the robustness of trifluoromethyl groups toward oxidative decomposition, suggest this ligand scaffold will be a useful platform in the study of oxidizing high-valent transition-metal species.
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Affiliation(s)
- Joseph S Scott
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Joseph E Schneider
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Eyob G Tewelde
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Joel G Gardner
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Sophie W Anferov
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Alexander S Filatov
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - John S Anderson
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
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4
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Ghadwal RS. 1,3-Imidazole-Based Mesoionic Carbenes and Anionic Dicarbenes: Pushing the Limit of Classical N-Heterocyclic Carbenes. Angew Chem Int Ed Engl 2023; 62:e202304665. [PMID: 37132480 DOI: 10.1002/anie.202304665] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 05/02/2023] [Accepted: 05/03/2023] [Indexed: 05/04/2023]
Abstract
Classical N-heterocyclic carbenes (NHCs) featuring the carbene center at the C2-position of 1,3-imidazole framework (i.e. C2-carbenes) are well acknowledged as very versatile neutral ligands in molecular as well as in materials sciences. The efficiency and success of NHCs in diverse areas is essentially attributed to their persuasive stereoelectronics, in particular the potent σ-donor property. The NHCs with the carbene center at the unusual C4 (or C5) position, the so-called abnormal NHCs (aNHCs) or mesoionic carbenes (iMICs), are however superior σ-donors than C2-carbenes. Hence, iMICs have substantial potential in sustainable synthesis and catalysis. The main obstacle in this direction is rather demanding synthetic accessibility of iMICs. The aim of this review article is to highlight recent advances, particularly by the author's research group, in accessing stable iMICs, quantifying their properties, and exploring their applications in synthesis and catalysis. In addition, the synthetic viability and use of vicinal C4,C5-anionic dicarbenes (ADCs), also based on an 1,3-imidazole framework, are presented. As will be apparent on following pages, iMICs and ADCs hold potentials in pushing the limit of classical NHCs by enabling access to conceptually new main-group heterocycles, radicals, molecular catalysts, ligands sets, and more.
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Affiliation(s)
- Rajendra S Ghadwal
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, 33615, Bielefeld, Germany
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5
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Breitwieser K, Bahmann H, Weiss R, Munz D. Gauging Radical Stabilization with Carbenes. Angew Chem Int Ed Engl 2022; 61:e202206390. [PMID: 35796423 PMCID: PMC9545232 DOI: 10.1002/anie.202206390] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Indexed: 11/29/2022]
Abstract
Carbenes, including N‐heterocyclic carbene (NHC) ligands, are used extensively to stabilize open‐shell transition metal complexes and organic radicals. Yet, it remains unknown, which carbene stabilizes a radical well and, thus, how to design radical‐stabilizing C‐donor ligands. With the large variety of C‐donor ligands experimentally investigated and their electronic properties established, we report herein their radical‐stabilizing effect. We show that radical stabilization can be understood by a captodative frontier orbital description involving π‐donation to‐ and π‐donation from the carbenes. This picture sheds a new perspective on NHC chemistry, where π‐donor effects usually are assumed to be negligible. Further, it allows for the intuitive prediction of the thermodynamic stability of covalent radicals of main group‐ and transition metal carbene complexes, and the quantification of redox non‐innocence.
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Affiliation(s)
- Kevin Breitwieser
- Coordination Chemistry Saarland University Campus C4.1 66123 Saarbrücken Germany
| | - Hilke Bahmann
- Physical and Theoretical Chemistry Saarland University Campus B2.2 66123 Saarbrücken Germany
| | - Robert Weiss
- Organische Chemie Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg Henkestr. 42 91054 Erlangen Germany
| | - Dominik Munz
- Coordination Chemistry Saarland University Campus C4.1 66123 Saarbrücken Germany
- Inorganic and General Chemistry Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg Egerlandstr. 1 91058 Erlangen Germany
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6
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Breitwieser K, Bahmann H, Weiss R, Munz D. Gauging Radical Stabilization with Carbenes. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202206390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Kevin Breitwieser
- Saarland University: Universitat des Saarlandes Coordination Chemistry GERMANY
| | - Hilke Bahmann
- Saarland University: Universitat des Saarlandes Theoretical Chemistry GERMANY
| | - Robert Weiss
- FAU Erlangen Nuremberg: Friedrich-Alexander-Universitat Erlangen-Nurnberg Organic Chemistry GERMANY
| | - Dominik Munz
- Universitat des Saarlandes Inorganic Chemistry: Coordination Chemistry Campus C 4.1 66123 Saarbrücken GERMANY
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7
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Dong Z, Sienkiewicz A, Suleymanov AA, Berton C, Fadaei‐Tirani F, Scopelliti R, Severin K. A Mesoionic Diselenolene Anion and the Corresponding Radical Dianion. Chemistry 2022; 28:e202200893. [PMID: 35388932 PMCID: PMC9322424 DOI: 10.1002/chem.202200893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Indexed: 11/09/2022]
Abstract
Dichalcogenolenes are archetypal redox non‐innocent ligands with numerous applications. Herein, a diselenolene ligand with fundamentally different electronic properties is described. A mesoionic diselenolene was prepared by selenation of a C2‐protected imidazolium salt. This ligand is diamagnetic, which is in contrast to the paramagnetic nature of standard dichalcogenolene monoanions. The new ligand is also redox‐active, as demonstrated by isolation of a stable diselenolene radical dianion. The unique electronic properties of the new ligand give rise to unusual coordination chemistry. Thus, preparation of a hexacoordinate aluminum tris(diselenolene) complex and a Lewis acidic aluminate complex with two ligand‐centered unpaired electrons was achieved.
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Affiliation(s)
- Zhaowen Dong
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Andrzej Sienkiewicz
- Institute of Physics École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
- ADSresonances Sàrl Route de Genève 60B 1028 Préverenges Switzerland
| | - Abdusalom A. Suleymanov
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Cesare Berton
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Farzaneh Fadaei‐Tirani
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Rosario Scopelliti
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Kay Severin
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
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8
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Neururer F, Liu S, Leitner D, Baltrun M, Fisher KR, Kopacka H, Wurst K, Daumann LJ, Munz D, Hohloch S. Mesoionic Carbenes in Low- to High-Valent Vanadium Chemistry. Inorg Chem 2021; 60:15421-15434. [PMID: 34590834 PMCID: PMC8527456 DOI: 10.1021/acs.inorgchem.1c02087] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Indexed: 12/12/2022]
Abstract
We report the synthesis of vanadium(V) oxo complex 1 with a pincer-type dianionic mesoionic carbene (MIC) ligand L1 and the general formula [VOCl(L1)]. A comparison of the structural (SC-XRD), electronic (UV-vis), and electrochemical (cyclic voltammetry) properties of 1 with the benzimidazolinylidene congener 2 (general formula [VOCl(L2)]) shows that the MIC is a stronger donor also for early transition metals with low d-electron population. Since electrochemical studies revealed both complexes to be reversibly reduced, the stronger donor character of MICs was not only demonstrated for the vanadium(V) but also for the vanadium(IV) oxidation state by isolating the reduced vanadium(IV) complexes [Co(Cp*)2][1] and [Co(Cp*)2][2] ([Co(Cp*)2] = decamethylcobaltocenium). The electronic structures of the compounds were investigated by computational methods. Complex 1 was found to be a moderate precursor for salt metathesis reactions, showing selective reactivity toward phenolates or secondary amides, but not toward primary amides and phosphides, thiophenols, or aryls/alkyls donors. Deoxygenation with electron-rich phosphines failed to give the desired vanadium(III) complex. However, treatment of the deprotonated ligand precursor with vanadium(III) trichloride resulted in the clean formation of the corresponding MIC vanadium(III) complex 6, which undergoes a clean two-electron oxidation with organic azides yielding the corresponding imido complexes. The reaction with TMS-N3 did not afford a nitrido complex, but instead the imido complex 10. This study reveals that, contrary to popular belief, MICs are capable of supporting early transition-metal complexes in a variety of oxidation states, thus making them promising candidates for the activation of small molecules and redox catalysis.
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Affiliation(s)
- Florian
R. Neururer
- Institute
of Inorganic, General and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria
| | - Shenyu Liu
- Faculty
of Science, Department of Chemistry, University
of Paderborn, Warburger Straße 100, 33098 Paderborn, Germany
| | - Daniel Leitner
- Institute
of Inorganic, General and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria
| | - Marc Baltrun
- Faculty
of Science, Department of Chemistry, University
of Paderborn, Warburger Straße 100, 33098 Paderborn, Germany
| | - Katherine R. Fisher
- Department
Chemie, Ludwigs-Maximilians-University Munich, Butenandtstraße 5-13 Haus D, 81377 Munich, Germany
| | - Holger Kopacka
- Institute
of Inorganic, General and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria
| | - Klaus Wurst
- Institute
of Inorganic, General and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria
| | - Lena J. Daumann
- Department
Chemie, Ludwigs-Maximilians-University Munich, Butenandtstraße 5-13 Haus D, 81377 Munich, Germany
| | - Dominik Munz
- Fakultät
NT, Inorganic Chemistry: Coordination Chemistry, Saarland University, Campus C4.1, 66123 Saarbrücken, Germany
| | - Stephan Hohloch
- Institute
of Inorganic, General and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria
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Dong Z, Blaskovits JT, Fadaei-Tirani F, Scopelliti R, Sienkiewicz A, Corminboeuf C, Severin K. Tuning the π-Accepting Properties of Mesoionic Carbenes: A Combined Computational and Experimental Study. Chemistry 2021; 27:11983-11988. [PMID: 34105837 PMCID: PMC8456875 DOI: 10.1002/chem.202101742] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Indexed: 02/02/2023]
Abstract
Mesoionic imidazolylidenes are recognized as excellent electron‐donating ligands in organometallic and main group chemistry. However, these carbene ligands typically show poor π‐accepting properties. A computational analysis of 71 mesoionic imidazolylidenes that bear different aryl or heteroaryl substituents in C2 position was performed. The study has revealed that a diphenyltriazinyl (Dpt) substituent renders the corresponding carbene particularly π‐acidic. The computational results could be corroborated experimentally. A mesoionic imidazolylidene with a Dpt substituent was found to be a better σ‐donor and a better π‐acceptor compared to an Arduengo‐type N‐heterocyclic carbene. To demonstrate the utility of the new carbene, the ligand was used to stabilize a low‐valent paramagnetic tin compound.
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Affiliation(s)
- Zhaowen Dong
- Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - J Terence Blaskovits
- Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Farzaneh Fadaei-Tirani
- Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Rosario Scopelliti
- Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Andrzej Sienkiewicz
- Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.,ADSresonances Sarl, Route de Genève 60B, 1028, Préverenges, Switzerland
| | - Clémence Corminboeuf
- Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Kay Severin
- Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
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