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Fischer TE, Janetzki JT, M Zahir FZ, Gable RW, Starikova AA, Boskovic C. Tuning valence tautomerism in a family of dinuclear cobalt complexes incorporating a conjugated bridging bis(dioxolene) ligand with weak communication. Dalton Trans 2024. [PMID: 38236053 DOI: 10.1039/d3dt04162j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Valence tautomerism (VT) involves the stimulated reversible intramolecular electron transfer between a redox-active metal and ligand. Dinuclear cobalt complexes bridged by bis(dioxolene) ligands can undergo thermally-induced VT with access to {CoIII-cat-cat-CoIII}, {CoIII-cat-SQ-CoII} and {CoII-SQ-SQ-CoII} states (cat2- = catecholate, SQ˙- = semiquinonate, CoIII refers to low spin CoIII, CoII refers to high spin CoII). The resulting potential for two-step VT interconversions offers increased functionality over mononuclear examples. In this study, the bis(dioxolene) ligand 3,3',4,4'-tetrahydroxy-5,5'-dimethoxy-benzaldazine (thMH4) was paired with Mentpa (tpa = tris(2-pyridylmethyl)amine, n = 0-3 corresponds to methylation at 6-position of the pyridine rings) to afford [{Co(Mentpa)}2(thM)](PF6)2 (1a, n = 0; 2a, n = 2; 3a, n = 3). Structural, magnetic susceptibility and spectroscopic data show that 1a and 3a remain in the temperature invariant {CoIII-cat-cat-CoIII} and {CoII-SQ-SQ-CoII} forms in the solid state, respectively. In contrast, 2a exhibits incomplete thermally-induced VT between these two tautomeric forms via the mixed {CoIII-cat-SQ-CoII} tautomer. In solution, room temperature electronic absorption spectra are consistent with the assignments from the solid-state, with VT observed only for 2a. From electrochemistry, the proximity of the two 1e--processes for the thMn- ligand indicates weak electronic communication between the two dioxolene units, supporting the potential for a two-step VT interconversion in thMn- containing complexes. Comparison of the redox potentials of the Co and thMn- processes suggests that only 2a has these processes in sufficient proximity to afford the thermally-induced VT observed experimentally. Density functional theory calculations are consistent with the prerequisite energy ordering for a two-step transition for 2a, and temperature invariant {CoIII-cat-cat-CoIII} and {CoII-SQ-SQ-CoII} states for 1a and 3a, respectively. This work presents the third example, and the first formally conjugated example, of a bridging bis(dioxolene) ligand that can afford two-step VT in a Co complex, suggesting new possibilities towards applications based on multistep switching.
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Affiliation(s)
- Tristan E Fischer
- School of Chemistry, University of Melbourne, Parkville, 3010 Victoria, Australia.
| | - Jett T Janetzki
- School of Chemistry, University of Melbourne, Parkville, 3010 Victoria, Australia.
| | - F Zahra M Zahir
- School of Chemistry, University of Melbourne, Parkville, 3010 Victoria, Australia.
| | - Robert W Gable
- School of Chemistry, University of Melbourne, Parkville, 3010 Victoria, Australia.
| | - Alyona A Starikova
- Institute of Physical and Organic Chemistry, Southern Federal University, 344090, Rostov-on-Don, Russian Federation
| | - Colette Boskovic
- School of Chemistry, University of Melbourne, Parkville, 3010 Victoria, Australia.
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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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Raithel AL, Meador WE, Kim TY, Staples RJ, Delcamp JH, Hamann TW. Molecular Switch Cobalt Redox Shuttle with a Tunable Hexadentate Ligand. J Am Chem Soc 2023; 145:1367-1377. [PMID: 36595559 DOI: 10.1021/jacs.2c12017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Strong-field hexadentate ligands were synthesized and coordinated to cobalt metal centers to result in three new low-spin to low-spin Co(III/II) redox couples. The ligand backbone has been modified with dimethyl amine groups to result in redox potential tuning of the Co(III/II) redox couples from -200 to -430 mV versus Fc+/0. The redox couples surprisingly undergo a reversible molecular switch rearrangement from five-coordinate Co(II) to six-coordinate Co(III) despite the ligands being hexadentate. The complexes exhibit modestly faster electron self-exchange rate constants of 2.2-4.2 M-1 s-1 compared to the high-spin to low-spin redox couple [Co(bpy)3]3+/2+ at 0.27 M-1 s-1, which is attributed to the change in spin state being somewhat offset by this coordination switching behavior. The complexes were utilized as redox shuttles in dye-sensitized solar cells with the near-IR AP25 + D35 dye system and exhibited improved photocurrents over the [Co(bpy)3]3+/2+ redox shuttle (19.8 vs 18.0 mA/cm2). Future directions point toward pairing the low-spin to low-spin Co(II/III) tunable series to dyes with significantly more negative highest occupied molecular orbital potentials that absorb into the near-IR where outer sphere redox shuttles have failed to produce efficient dye regeneration.
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Affiliation(s)
- Austin L Raithel
- Department of Chemistry, Michigan State University, 578 S Shaw Lane, East Lansing, Michigan48823, United States
| | - William E Meador
- Department of Chemistry and Biochemistry, Coulter Hall, University of Mississippi, University, Mississippi38677, United States
| | - Tea-Yon Kim
- Department of Chemistry, Michigan State University, 578 S Shaw Lane, East Lansing, Michigan48823, United States
| | - Richard J Staples
- Department of Chemistry, Michigan State University, 578 S Shaw Lane, East Lansing, Michigan48823, United States
| | - Jared H Delcamp
- UES, Inc. Research Scientist, Air Force Research Labs, Materials and Manufacturing Directorate, 2230 Tenth Street B655 R198, WPAFB, Ohio45433-7817, United States
| | - Thomas W Hamann
- Department of Chemistry, Michigan State University, 578 S Shaw Lane, East Lansing, Michigan48823, United States
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Computational search for radical-bearing stilbene derivatives with switchable magnetic properties. Russ Chem Bull 2022. [DOI: 10.1007/s11172-022-3542-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Chegerev MG, Starikova AA. A computational search for spin-crossover in bis(catecholate) diiron complexes. COMPUT THEOR CHEM 2022. [DOI: 10.1016/j.comptc.2022.113693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Starikova AA, Chegerev MG, Starikov AG, Minkin VI. o-Benzoquinone Cobalt Complexes Bearing Organosilicon Radicals: Quantum-Chemical Study. RUSS J COORD CHEM+ 2022. [DOI: 10.1134/s1070328422040054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Heterospin iron complexes with dioxolenes functionalized with stable radicals: quantum chemical study. Russ Chem Bull 2022. [DOI: 10.1007/s11172-021-3347-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Protasenko NA, Poddelskii AI, Rumyantsev RV, Yakushev IA, Cherkasov VK. Cobalt(III) Bis-o-semiquinone Complexes with 1-Aryl-3,5-Diphenylformazan Ligands: Synthesis, Structures, and Magnetic Properties. RUSS J COORD CHEM+ 2021. [DOI: 10.1134/s1070328421100067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Starikov AG, Starikova AA, Chegerev MG, Aldoshin SM, Metelitsa AV, Minkin VI. Spin‐State‐Switching Rearrangements of Bis(dioxolene)‐Bridged CrCo Complexes: A DFT Study. Eur J Inorg Chem 2021. [DOI: 10.1002/ejic.202100702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Andrey G. Starikov
- 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
| | - Maxim G. Chegerev
- Institute of Physical and Organic Chemistry Southern Federal University 194/2 Stachka Avenue 344090 Rostov-on-Don Russian Federation
| | - Sergey M. Aldoshin
- Institute of Problems of Chemical Physics Russian Academy of Sciences 1 Acad. Semenov Avenue 142432 Chernogolovka Russian Federation
| | - Anatoly V. Metelitsa
- Institute of Physical and Organic Chemistry Southern Federal University 194/2 Stachka Avenue 344090 Rostov-on-Don Russian Federation
| | - Vladimir I. Minkin
- Institute of Physical and Organic Chemistry Southern Federal University 194/2 Stachka Avenue 344090 Rostov-on-Don Russian Federation
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Chegerev MG, Starikov AG, Starikova AA. Quantum Chemical Study of Spin Transitions in the Bimetallic Fe/Co Complexes with the Bis(catecholate) Bridging Ligand. RUSS J COORD CHEM+ 2021. [DOI: 10.1134/s1070328421090013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Abstract
The computational modeling of the spatial and electronic structures, energy characteristics, and magnetic properties of the bimetallic iron and cobalt complexes with 9,10-dimethyl-9,10-ethano-9,10-dihydro-2,3,6,7-tetrahydroxyanthracene and terminal tris(2-pyridylmethyl)amine bases is performed using the density functional theory method (DFT UTPSSh/6-311++G(d,p)). The chosen tetradentate redox ligand is shown to be a promising precursor for the production of magnetically active compounds. The calculations make it possible to establish a relationship between the relative energies of the electronic isomers of the complexes and the structures of the ancillary N-donor moieties. The coordination compounds prone to the manifestation of spin transitions accompanied by a change in the magnetic properties are revealed.
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