1
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Manna F, Oggianu M, Galán-Mascarós JR, Pop F, Le Guennic B, Mercuri ML, Avarvari N. Tuning the slow magnetic relaxation with the substituents in anilate bridged bis(dysprosium) complexes. Dalton Trans 2024; 53:8369-8381. [PMID: 38669068 DOI: 10.1039/d4dt00175c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/15/2024]
Abstract
Dinuclear lanthanide complexes [((HB(pz)3)2Dy)2(μ-Th2An)] (1Dy) and [((HB(pz)3)2Dy)2(μ-ClCNAn)] (2Dy), based on the hydrotris(pyrazol-1-yl)borate (HBpz3-) scorpionate capping ligand and anilate (An2-) bridging linkers, namely homosubstituted dithiophene- and heterosubstituted chlorocyanoanilate, bearing electron-donating and withdrawing substituents at the 3,6-positions of the benzoquinone core, are reported. 1Dy shows an octacoordinated {N6O2} DyIII ion within a D4h distorted square antiprismatic coordination, an ideal geometry for Single-Molecule Magnet (SMM) behavior, given its oblate nature, whereas in 2Dy the octacoordinated DyIII ion adopts a D2d triangular dodecahedron geometry, while maintaining the same {N6O2} coordination sphere. Both complexes show field-induced single molecule magnet (SMM) behaviour, with tuning of the slow magnetic relaxation as a function of the nature of the substituents at the 3,6-positions of the anilate moiety. A comparison of the Arrhenius fitting parameters for 1Dy and 2Dy supports the hypothesis that square antiprismatic DyIII complexes, as 1Dy, exhibit higher energy barriers. This interpretation is supported by ab initio calculations that also shed light on the crucial role of intermolecular dipolar interactions.
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Affiliation(s)
- Fabio Manna
- Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, I-09042 Monserrato, Italy.
- Univ Angers, CNRS, MOLTECH-ANJOU, SFR MATRIX, F-49000 Angers, France.
- INSTM, Via Giuseppe Giusti, 9, 50121 Firenze, Italy
| | - Mariangela Oggianu
- Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, I-09042 Monserrato, Italy.
- INSTM, Via Giuseppe Giusti, 9, 50121 Firenze, Italy
| | - José Ramón Galán-Mascarós
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST), Av. Països Catalans 16, E-43007 Tarragona, Spain
- ICREA, Passeig Lluis Companys, 23, Barcelona 08010, Spain
| | - Flavia Pop
- Univ Angers, CNRS, MOLTECH-ANJOU, SFR MATRIX, F-49000 Angers, France.
| | - Boris Le Guennic
- Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, F-35000 Rennes, France
| | - Maria Laura Mercuri
- Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, I-09042 Monserrato, Italy.
- INSTM, Via Giuseppe Giusti, 9, 50121 Firenze, Italy
| | - Narcis Avarvari
- Univ Angers, CNRS, MOLTECH-ANJOU, SFR MATRIX, F-49000 Angers, France.
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2
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Lien CY, Boyn JN, Anferov SW, Mazziotti DA, Anderson JS. Origin of Weak Magnetic Coupling in a Dimanganese(II) Complex Bridged by the Tetrathiafulvalene-Tetrathiolate Radical. Inorg Chem 2023; 62:19488-19497. [PMID: 37967380 DOI: 10.1021/acs.inorgchem.3c02534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2023]
Abstract
Magnetic exchange coupling (J) between different spin centers plays a crucial role in molecule-based magnetic materials. Direct exchange coupling between an organic radical and a metal is frequently stronger than superexchange through diamagnetic ligands, and the strategy of using organic radicals to engender desirable magnetic properties has been an area of active investigation. Despite significant advances and exciting bulk properties, the magnitude of J for radical linkers bridging paramagnetic centers is still difficult to rationally predict. It is thus important to elucidate the features of organic radicals that govern this parameter. Here, we measure J for the tetrathiafulvalene-tetrathiolate radical (TTFtt3-•) in a dinuclear Mn(II) complex. Magnetometry studies show that the antiferromagnetic coupling in this complex is much weaker than that in related Mn(II)-radical compounds, in contrast to what might be expected for the S-based chelating donor atoms of TTFtt. Experimental and computational analyses suggest that this small J coupling may be attributed to poor overlap between Mn- and TTFtt-based magnetic orbitals coupled with insignificant spin density on the coordinating S-atoms. These factors override any expected increase in J from the comparatively strong S-donors. This work elucidates the magnetic coupling properties of the TTFtt3-• radical for the first time and also demonstrates how multiple competing factors must be considered in rationally designing organic radical ligands for molecular-based magnetic compounds.
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Affiliation(s)
- Chen-Yu Lien
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Jan-Niklas Boyn
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Sophie W Anferov
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - David A Mazziotti
- 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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3
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Janetzki JT, Chegerev MG, Gransbury GK, Gable RW, Clegg JK, Mulder RJ, Jameson GNL, Starikova AA, Boskovic C. Controlling Spin Crossover in a Family of Dinuclear Fe(III) Complexes via the Bis(catecholate) Bridging Ligand. Inorg Chem 2023; 62:15719-15735. [PMID: 37691232 DOI: 10.1021/acs.inorgchem.3c02598] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Spin crossover (SCO) complexes can reversibly switch between low spin (LS) and high spin (HS) states, affording possible applications in sensing, displays, and molecular electronics. Dinuclear SCO complexes with access to [LS-LS], [LS-HS], and [HS-HS] states may offer increased levels of functionality. The nature of the SCO interconversion in dinuclear complexes is influenced by the local electronic environment. We report the synthesis and characterization of [{FeIII(tpa)}2spiro](PF6)2 (1), [{FeIII(tpa)}2Br4spiro](PF6)2 (2), and [{FeIII(tpa)}2thea](PF6)2 (3) (tpa = tris(2-pyridylmethyl)amine, spiroH4 = 3,3,3',3'-tetramethyl-1,1'-spirobi(indan)-5,5',6,6'-tetraol, Br4spiroH4 = 3,3,3',3'-tetramethyl-1,1'-spirobi(indan)-4,4',7,7'-tetrabromo-5,5',6,6'-tetraol, theaH4 = 2,3,6,7-tetrahydroxy-9,10-dimethyl-9,10-dihydro-9,10-ethanoanthracene), utilizing non-conjugated bis(catecholate) bridging ligands. In the solid state, magnetic and structural analysis shows that 1 remains in the [HS-HS] state, while 2 and 3 undergo a partial SCO interconversion upon cooling from room temperature involving the mixed [LS-HS] state. In solution, all complexes undergo SCO from [HS-HS] at room temperature, via [LS-HS] to mixtures including [LS-LS] at 77 K, with the extent of SCO increasing in the order 1 < 2 < 3. Gas phase density functional theory calculations suggest a [LS-LS] ground state for all complexes, with the [LS-HS] and [HS-HS] states successively destabilized. The relative energy separations indicate that ligand field strength increases following spiro4- < Br4spiro4- < thea4-, consistent with solid-state magnetic and EPR behavior. All three complexes show stabilization of the [LS-HS] state in relation to the midpoint energy between [LS-LS] and [HS-HS]. The relative stability of the [LS-HS] state increases with increasing ligand field strength of the bis(catecholate) bridging ligand in the order 1 < 2 < 3. The bromo substituents of Br4spiro4- increase the ligand field strength relative to spiro4-, while the stronger ligand field provided by thea4- arises from extension of the overlapping π-orbital system across the two catecholate units. This study highlights how SCO behavior in dinuclear complexes can be modulated by the bridging ligand, providing useful insights for the design of molecules that can be interconverted between more than two states.
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Affiliation(s)
- Jett T Janetzki
- School of Chemistry, University of Melbourne, Victoria 3010, Australia
| | - Maxim G Chegerev
- Institute of Physical and Organic Chemistry, Southern Federal University, Rostov-on-Don 344090, Russian Federation
| | - Gemma K Gransbury
- Department of Chemistry, The University of Manchester, Manchester M13 9PL, U.K
| | - Robert W Gable
- School of Chemistry, University of Melbourne, Victoria 3010, Australia
| | - Jack K Clegg
- University of Queensland, St Lucia, Queensland 4072, Australia
| | | | - Guy N L Jameson
- School of Chemistry, University of Melbourne, Victoria 3010, Australia
| | - Alyona A Starikova
- Institute of Physical and Organic Chemistry, Southern Federal University, Rostov-on-Don 344090, Russian Federation
| | - Colette Boskovic
- School of Chemistry, University of Melbourne, Victoria 3010, Australia
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4
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Nguyen GT, Ungur L. The Role of Radical Bridges in Polynuclear Single‐Molecule Magnets. Chemistry 2022; 28:e202200227. [DOI: 10.1002/chem.202200227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Indexed: 11/08/2022]
Affiliation(s)
- Giang Truong Nguyen
- Department of Chemistry Faculty of Science National University of Singapore Block S8 Level 3, 3 Science Drive 3 Singapore Singapore 117543
| | - Liviu Ungur
- Department of Chemistry Faculty of Science National University of Singapore Block S8 Level 3, 3 Science Drive 3 Singapore Singapore 117543
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5
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Chegerev MG, Starikova AA. Electronic Lability of Quinonoid‐Bridged Dinuclear 3 d‐Metal Complexes with Tetradentate N‐Donor Bases. Eur J Inorg Chem 2021. [DOI: 10.1002/ejic.202100200] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Maxim G. Chegerev
- Institute of Physical and Organic Chemistry Southern Federal University 194/2 Stachka Avenue 344090 Rostov-on-Don Russian Federation
| | - Alyona A. Starikova
- Institute of Physical and Organic Chemistry Southern Federal University 194/2 Stachka Avenue 344090 Rostov-on-Don Russian Federation
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6
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Wang P, Saber MR, VanNatta PE, Yap GPA, Popescu CV, Scarborough CC, Kieber-Emmons MT, Dunbar KR, Riordan CG. Molecular and Electronic Structures and Single-Molecule Magnet Behavior of Tris(thioether)-Iron Complexes Containing Redox-Active α-Diimine Ligands. Inorg Chem 2021; 60:6480-6491. [PMID: 33840189 DOI: 10.1021/acs.inorgchem.1c00214] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Incorporating radical ligands into metal complexes is one of the emerging trends in the design of single-molecule magnets (SMMs). While significant effort has been expended to generate multinuclear transition metal-based SMMs with bridging radical ligands, less attention has been paid to mononuclear transition metal-radical SMMs. Herein, we describe the first α-diiminato radical-containing mononuclear transition metal SMM, namely, [κ2-PhTttBu]Fe(AdNCHCHNAd) (1), and its analogue [κ2-PhTttBu]Fe(CyNCHCHNCy) (2) (PhTttBu = phenyltris(tert-butylthiomethyl)borate, Ad = adamantyl, and Cy = cyclohexyl). 1 and 2 feature nearly identical geometric and electronic structures, as shown by X-ray crystallography and electronic absorption spectroscopy. A more detailed description of the electronic structure of 1 was obtained through EPR and Mössbauer spectroscopies, SQUID magnetometry, and DFT, TD-DFT, and CAS calculations. 1 and 2 are best described as high-spin iron(II) complexes with antiferromagnetically coupled α-diiminato radical ligands. A strong magnetic exchange coupling between the iron(II) ion and the ligand radical was confirmed in 1, with an estimated coupling constant J < -250 cm-1 (J = -657 cm-1, DFT). Calibrated CAS calculations revealed that the ground-state Fe(II)-α-diiminato radical configuration has significant ionic contributions, which are weighted specifically toward the Fe(I)-neutral α-diimine species. Experimental data and theoretical calculations also suggest that 1 possesses an easy-axis anisotropy, with an axial zero-field splitting parameter D in the range from -4 to-1 cm-1. Finally, dynamic magnetic studies show that 1 exhibits slow magnetic relaxation behavior with an energy barrier close to the theoretical maximum, 2|D|. These results demonstrate that incorporating strongly coupled α-diiminato radicals into mononuclear transition metal complexes can be an effective strategy to prepare SMMs.
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Affiliation(s)
- Peng Wang
- Department of Chemistry & Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Mohamed R Saber
- Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012, United States.,Department of Chemistry, Fayoum University, Fayoum 63514, Egypt
| | - Peter E VanNatta
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850, United States
| | - Glenn P A Yap
- Department of Chemistry & Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Codrina V Popescu
- Department of Chemistry, University of Saint Thomas, 2115 Summit Avenue, Saint Paul, Minnesota 55105, United States
| | - Christopher C Scarborough
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, United States.,Syngenta Crop Protection AG, Schaffhauserstrasse, CH-4332 Stein, Switzerland
| | | | - Kim R Dunbar
- Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012, United States
| | - Charles G Riordan
- Department of Chemistry & Biochemistry, University of Delaware, Newark, Delaware 19716, United States
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7
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Jung J, Legendre CM, Herbst-Irmer R, Stalke D. Exchange Coupling in Binuclear Manganese and Cobalt Complexes with the Tetraimido Sulfate Anion [S(N tBu) 4] 2. Inorg Chem 2021; 60:967-972. [PMID: 33378190 DOI: 10.1021/acs.inorgchem.0c03085] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The (hetero)bimetallic complexes [Cl2Mn(NtBu)2S(tBuN)2Mn{ClLi(THF)3}2] (1), [(acac)Co(NtBu)2S(tBuN)2Co(acac)] (2), and [(acac)Co(NtBu)2S(tBuN)2Li(THF)2] (3), with THF = tetrahydrofuran and acac = acetylacetonate [H2C(C(O)Me)2], were synthesized and investigated for their magnetic properties. While the two different MnII sites in 1 gave a weak coupling of J = -1.00 cm-1, we could observe an appreciable antiferromagnetic coupling of J = -6.08 cm-1 between the two CoII cations in 2, proving the tetraimido sulfate anion to be a challenging but promising linker to enhance magnetic communication between paramagnetic centers. The heterobimetallic complex 3 seems a versatile platform for magnetically interesting d/d, f/d, or f/f mixed-metal complexes.
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Affiliation(s)
- Jochen Jung
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, Göttingen 37077, Germany
| | - Christina M Legendre
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, Göttingen 37077, Germany
| | - Regine Herbst-Irmer
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, Göttingen 37077, Germany
| | - Dietmar Stalke
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, Göttingen 37077, Germany
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8
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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] [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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9
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Gould CA, Mu E, Vieru V, Darago LE, Chakarawet K, Gonzalez MI, Demir S, Long JR. Substituent Effects on Exchange Coupling and Magnetic Relaxation in 2,2′-Bipyrimidine Radical-Bridged Dilanthanide Complexes. J Am Chem Soc 2020; 142:21197-21209. [DOI: 10.1021/jacs.0c10612] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
| | | | - Veacheslav Vieru
- Theory of Nanomaterials Group, Katholieke Universiteit Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | | | | | | | - Selvan Demir
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Jeffrey R. Long
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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10
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Chakarawet K, Harris TD, Long JR. Semiquinone radical-bridged M 2 (M = Fe, Co, Ni) complexes with strong magnetic exchange giving rise to slow magnetic relaxation. Chem Sci 2020; 11:8196-8203. [PMID: 34123090 PMCID: PMC8163326 DOI: 10.1039/d0sc03078c] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 07/20/2020] [Indexed: 11/21/2022] Open
Abstract
The use of radical bridging ligands to facilitate strong magnetic exchange between paramagnetic metal centers represents a key step toward the realization of single-molecule magnets with high operating temperatures. Moreover, bridging ligands that allow the incorporation of high-anisotropy metal ions are particularly advantageous. Toward these ends, we report the synthesis and detailed characterization of the dinuclear hydroquinone-bridged complexes [(Me6tren)2MII 2(C6H4O2 2-)]2+ (Me6tren = tris(2-dimethylaminoethyl)amine; M = Fe, Co, Ni) and their one-electron-oxidized, semiquinone-bridged analogues [(Me6tren)2MII 2(C6H4O2 -˙)]3+. Single-crystal X-ray diffraction shows that the Me6tren ligand restrains the metal centers in a trigonal bipyramidal geometry, and coordination of the bridging hydro- or semiquinone ligand results in a parallel alignment of the three-fold axes. We quantify the p-benzosemiquinone-transition metal magnetic exchange coupling for the first time and find that the nickel(ii) complex exhibits a substantial J < -600 cm-1, resulting in a well-isolated S = 3/2 ground state even as high as 300 K. The iron and cobalt complexes feature metal-semiquinone exchange constants of J = -144(1) and -252(2) cm-1, respectively, which are substantially larger in magnitude than those reported for related bis(bidentate) semiquinoid complexes. Finally, the semiquinone-bridged cobalt and nickel complexes exhibit field-induced slow magnetic relaxation, with relaxation barriers of U eff = 22 and 46 cm-1, respectively. Remarkably, the Orbach relaxation observed for the Ni complex is in stark contrast to the fast processes that dominate relaxation in related mononuclear NiII complexes, thus demonstrating that strong magnetic coupling can engender slow magnetic relaxation.
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Affiliation(s)
- Khetpakorn Chakarawet
- Department of Chemistry, University of California Berkeley Berkeley California 94720 USA
| | - T David Harris
- Department of Chemistry, University of California Berkeley Berkeley California 94720 USA
| | - Jeffrey R Long
- Department of Chemistry, University of California Berkeley Berkeley California 94720 USA
- Department of Chemical and Biomolecular Engineering, University of California Berkeley Berkeley California 94720 USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory Berkeley California 94720 USA
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11
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Chandra S, Weisser F, Klenk S, Beerhues J, Schweinfurth D, Sarkar B. Dinuclear Ru II complexes with quinonoid bridges: tuning the electrochemical and spectroscopic properties of redox-switchable NIR dyes through judicious bridge design. Dalton Trans 2020; 49:8354-8366. [PMID: 32519683 DOI: 10.1039/d0dt01351j] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Bridging quinonoid ligands are important platforms for generating metal-based switchable optoelectronic and magnetic materials. A possible sound way of influencing the properties of the aforementioned materials is to modify the direct metal-ligand interface. We present herein a series of dinuclear RuII complexes where the set of donor atoms at the bridging quinonoid ligands range from [O,O,O,O], [O,O,O,N], [O,N,O,N] and [O,N,O,N']. Additionally, the substituents on the N-donors were varied as well (a total of eight different quinonoid bridges are compared). We also present a mononuclear RuII complex for comparison purposes. The dinuclear complexes act as switchable NIR dyes, absorbing in the NIR region in their mixed-valent RuII/RuIII form but not in the neighboring RuII/RuII and RuIII/RuIII states. The switching potentials (the potentials at which NIR absorptions appear) and the λmax of the NIR band can be fine-tuned by varying the donor atoms as well as the electron-donating ability of the substituents on the nitrogen atoms (tuning E by ca. 0.4 V and λmax by ca. 450 nm). Introducing more electron-rich substituents at the nitrogen atoms of the bridge results in higher band energies and more cathodic redox potentials. Unsymmetrical bridging ligands increase the thermodynamic stability of the mixed-valent state. Whereas almost all of the mixed-valent species presented here belong to the delocalised type III of the Robin-Day classification, the most unsymmetrical complex 2O,N(Mes) shows characteristic signs of a borderline Class-II-III compounds. This comprehensive study thus establishes the lesser used unsymmetrically substituted quinones as excellent bridges for generating and tuning a series of properties in their corresponding metal complexes.
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Affiliation(s)
- Shubhadeep Chandra
- Lehrstuhl für Anorganische Koordinationschemie, Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569, Stuttgart, Germany.
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12
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Alexandropoulos DI, Vignesh KR, Xie H, Dunbar KR. Quinoxaline radical-bridged transition metal complexes with very strong antiferromagnetic coupling. Chem Commun (Camb) 2020; 56:9122-9125. [DOI: 10.1039/d0cc03713c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synthesis, magnetic studies and, theoretical calculations of a new family of transition metal complexes bridged by a quinoxaline-based radical.
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Affiliation(s)
| | | | - Haomiao Xie
- Department of Chemistry
- Texas A&M University
- College Station
- USA
| | - Kim R. Dunbar
- Department of Chemistry
- Texas A&M University
- College Station
- USA
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