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Fleming C, Vu S, Brook DJR, Agrestini S, Pellegrin E, DaRos J. Metal-ligand interactions in a redox active ligand system. Electrochemistry and spectroscopy of [M(dipyvd) 2] n+ (M=Zn, Ni, n=0, 1, 2). Front Chem 2023; 11:1295289. [PMID: 38033468 PMCID: PMC10684738 DOI: 10.3389/fchem.2023.1295289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 10/27/2023] [Indexed: 12/02/2023] Open
Abstract
Reaction of nickel and zinc triflates with the tridentate leucoverdazyl 1-isopropyl-3,5-di (2'-pyridyl)-6-oxo-2H-tetrazine (dipyvdH) and triethylamine resulted in the neutral coordination compounds M(dipyvd)2 (M = Ni,Zn). In acetonitrile, both compounds undergo two one electron oxidation processes, Zn (dipyvd)2 at -0.28 V and -0.12 V and Ni(dipyvd)2 at -0.32 V and -0.15 V vs ferrocene/ferricenium. Oxidations are ligand based resulting in an intermediate mixed valence species and a cationic bis(verdazyl) compound respectively. Oxidation of the ligand changes a localized, antiaromatic, non-planar 8π electron anion to a planar, delocalized 7π electron radical. The change in ligand structure results in an increase in the octahedral ligand field splitting from 10,500 cm-1 to ∼13,000 cm-1, suggesting an increase in the pi acceptor character of the ligand. In the mixed valence species, spectroscopic data suggests minimal interaction between ligands mediated by the metal center; i.e., these are class I-II systems in the Robin-Day classification.
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Affiliation(s)
- Connor Fleming
- Department of Chemistry, San Jose State University, San Jose, CA, United States
| | - Son Vu
- Department of Chemistry, San Jose State University, San Jose, CA, United States
| | - David J. R. Brook
- Department of Chemistry, San Jose State University, San Jose, CA, United States
| | - Stefano Agrestini
- ALBA Synchrotron Light Source, E-08290 Cerdanyola del Vallès, Barcelona, Spain
| | - Eric Pellegrin
- ALBA Synchrotron Light Source, E-08290 Cerdanyola del Vallès, Barcelona, Spain
| | - Jeffrey DaRos
- Department of Chemistry, San Jose State University, San Jose, CA, United States
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Roseiro P, Petit L, Robert V, Yalouz S. Emergence of Spinmerism for Molecular Spin-Qubits Generation. Chemphyschem 2023; 24:e202200478. [PMID: 36161748 DOI: 10.1002/cphc.202200478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 09/20/2022] [Indexed: 01/20/2023]
Abstract
Molecular platforms are regarded as promising candidates in the generation of units of information for quantum computing. Herein, a strategy combining spin-crossover metal ions and radical ligands is proposed from a model Hamiltonian first restricted to exchange interactions. Unusual spin states structures emerge from the linkage of a singlet/triplet commutable metal centre with two doublet-radical ligands. The ground state nature is modulated by charge transfers and can exhibit a mixture of triplet and singlet local metal spin states. Besides, the superposition reaches a maximum for 2 K M = K 1 + K 2 ${2{K}_{M}={K}_{1}+{K}_{2}}$ , suggesting a necessary competition between the intramolecular K M ${{K}_{M}}$ and inter-metal-ligand K 1 ${{K}_{1}}$ and K 2 ${{K}_{2}}$ direct exchange interactions. The results promote spinmerism, an original manifestation of quantum entanglement between the spin states of a metal centre and radical ligands. The study provides insights into spin-coupled compounds and inspiration for the development of molecular spin-qubits.
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Affiliation(s)
- Pablo Roseiro
- Laboratoire de Chimie Quantique, Institut de Chimie, CNRS/, Université de Strasbourg, 4 rue Blaise Pascal, 67000, Strasbourg, France
| | - Louis Petit
- Laboratoire de Chimie Quantique, Institut de Chimie, CNRS/, Université de Strasbourg, 4 rue Blaise Pascal, 67000, Strasbourg, France
| | - Vincent Robert
- Laboratoire de Chimie Quantique, Institut de Chimie, CNRS/, Université de Strasbourg, 4 rue Blaise Pascal, 67000, Strasbourg, France
| | - Saad Yalouz
- Laboratoire de Chimie Quantique, Institut de Chimie, CNRS/, Université de Strasbourg, 4 rue Blaise Pascal, 67000, Strasbourg, France
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Lohmeyer L, Kaifer E, Enders M, Himmel H. Switching from Metal- to Ligand-Based Oxidation in Cobalt Complexes with Redox-Active Bisguanidine Ligands. Chemistry 2021; 27:11852-11867. [PMID: 34101917 PMCID: PMC8457109 DOI: 10.1002/chem.202101364] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Indexed: 11/19/2022]
Abstract
The control of the redox reactivity, magnetic and optical properties of the different redox states of complexes with redox‐active ligands permits their rational use in catalysis and materials science. The redox‐chemistry of octahedrally coordinated high‐spin CoII complexes (three unpaired electrons) with one redox‐active bisguanidine ligand and two acetylacetonato (acac) co‐ligands is completely changed by replacing the acac by hexafluoro‐acetylacetonato (hfacac) co‐ligands. The first one‐electron oxidation is metal‐centered in the case of the complexes with acac co‐ligands, giving diamagnetic CoIII complexes. By contrast, in the case of the less Lewis‐basic hfacac co‐ligands, the first one‐electron oxidation becomes ligand‐centered, leading to high‐spin CoII complexes with a radical monocationic guanidine ligand unit (four unpaired electrons). Ferromagnetic coupling between the spins on the metal and the organic radical in solution is evidenced by temperature‐dependent paramagnetic NMR studies, allowing to estimate the isotropic exchange coupling constant in solution. Second one‐electron oxidation leads to high‐spin CoII complexes with dicationic guanidine ligand units (three unpaired electrons) in the presence of hfacac co‐ligands, but to low‐spin CoIII complexes with radical monocationic, peralkylated guanidine ligand (one unpaired electron) in the presence of acac co‐ligands. The analysis of the electronic structures is complemented by quantum‐chemical calculations on the spin density distributions and relative energies of the possible redox isomers.
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Affiliation(s)
- Lukas Lohmeyer
- Inorganic ChemistryRuprecht-Karls University of HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Elisabeth Kaifer
- Inorganic ChemistryRuprecht-Karls University of HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Markus Enders
- Inorganic ChemistryRuprecht-Karls University of HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Hans‐Jörg Himmel
- Inorganic ChemistryRuprecht-Karls University of HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
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Mavragani N, Kitos AA, Brusso JL, Murugesu M. Enhancing Magnetic Communication between Metal Centres: The Role of s-Tetrazine Based Radicals as Ligands. Chemistry 2021; 27:5091-5106. [PMID: 33079452 DOI: 10.1002/chem.202004215] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/19/2020] [Indexed: 12/31/2022]
Abstract
Although 1,2,4,5-tetrazines or s-tetrazines have been known in the literature for more than a century, their coordination chemistry has become increasingly popular in recent years due to their unique redox activity, multiple binding sites and their various applications. The electron-poor character of the ring and stabilization of the radical anion through all four nitrogen atoms in their metal complexes provide new aspects in molecular magnetism towards the synthesis of new high performing Single Molecule Magnets (SMMs). The scope of this review is to examine the role of s-tetrazine radical ligands in transition metal and lanthanide based SMMs and provide a critical overview of the progress thus far in this field. As well, general synthetic routes and new insights for the preparation of s-tetrazines are discussed, along with their redox activity and applications in various fields. Concluding remarks along with the limitations and perspectives of these ligands are discussed.
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Affiliation(s)
- Niki Mavragani
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie, Ottawa, Ontario, K1N 6N5, Canada
| | - Alexandros A Kitos
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie, Ottawa, Ontario, K1N 6N5, Canada
| | - Jaclyn L Brusso
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie, Ottawa, Ontario, K1N 6N5, Canada
| | - Muralee Murugesu
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, 10 Marie Curie, Ottawa, Ontario, K1N 6N5, Canada
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Ehret F, Filippou V, Blickle S, Bubrin M, Záliš S, Kaim W. Structural and Oxidation State Alternatives in Platinum and Palladium Complexes of a Redox-Active Amidinato Ligand. Chemistry 2021; 27:3374-3381. [PMID: 32959415 PMCID: PMC7986709 DOI: 10.1002/chem.202003636] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Indexed: 11/07/2022]
Abstract
Reaction of [Pt(DMSO)2 Cl2 ] or [Pd(MeCN)2 Cl2 ] with the electron-rich LH=N,N'-bis(4-dimethylaminophenyl)ethanimidamide yielded mononuclear [PtL2 ] (1) but dinuclear [Pd2 L4 ] (2), a paddle-wheel complex. The neutral compounds were characterized through experiments (crystal structures, electrochemistry, UV-vis-NIR spectroscopy, magnetic resonance) and TD-DFT calculations as metal(II) species with noninnocent ligands L- . The reversibly accessible cations [PtL2 ]+ and [Pd2 L4 ]+ were also studied, the latter as [Pd2 L4 ][B{3,5-(CF3 )2 C6 H3 }4 ] single crystals. Experimental and computational investigations were directed at the elucidation of the electronic structures, establishing the correct oxidation states within the alternatives [PtII (L- )2 ] or [Pt. (L )2 ], [PtII (L0.5- )2 ]+ or [PtIII (L- )2 ]+ , [(PdII )2 (μ-L- )4 ] or [(Pd1.5 )2 (μ-L0.75- )4 ], and [(Pd2.5 )2 (μ-L- )4 ]+ or [(PdII )2 (μ-L0.75- )4 ]+ . In each case, the first alternative was shown to be most appropriate. Remarkable results include the preference of platinum for mononuclear planar [PtL2 ] with an N-Pt-N bite angle of 62.8(2)° in contrast to [Pd2 L4 ], and the dimetal (Pd2 4+ →Pd2 5+ ) instead of ligand (L- →L ) oxidation of the dinuclear palladium compound.
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Affiliation(s)
- Fabian Ehret
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70550, Stuttgart, Germany
| | - Vasileios Filippou
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70550, Stuttgart, Germany
| | - Svenja Blickle
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70550, Stuttgart, Germany
| | - Martina Bubrin
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70550, Stuttgart, Germany
| | - Stanislav Záliš
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, 18223, Prague, Czech Republic
| | - Wolfgang Kaim
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70550, Stuttgart, Germany
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