Temperature-Induced Solid-State Valence Tautomeric Interconversion in Two Cobalt−Schiff Base Diquinone Complexes

Cador, Olivier; Chabre, F.; Dei, Andrea; Sangregorio, Claudio; Slageren, Joris van; Vaz, Maria G. F.

doi:10.1021/ic034210z

Cited by 62 publications

(55 citation statements)

References 42 publications

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“…[2][3][4][5][6] The electronic structure is often influenced by a number of parameters, such as temperature, pressure, modifications of the coligands, the environment (solid state or solution), the solvent, and for charged complexes, even the counterions. [7][8][9][10] Most studied valence tautomeric transition-metal complexes are based on cobalt, [11] for which the change from the Co II high-spin to Co III low-spin state is associated with a relative high barrier. Initially, the studies concentrated on mononuclear complexes, but recently research on dinuclear cobalt complexes with bis(dioxolene) ligands was intensified due to their potential as materials with molecular-based switchable paramagnetic units (molecular spintronics).…”

Section: Introductionmentioning

confidence: 99%

A Valence Tautomeric Dinuclear Copper Tetrakisguanidine Complex

Wiesner

Wagner

Kaifer

et al. 2016

Chemistry A European J

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We report on the first valence tautomeric dinuclear copper complex, featuring 2,3,5,6-tetrakis(tetramethylguanidino)pyridine as a bridging redox-active GFA (guanidino-functionalized aromatic) ligand. The preferred electronic structure of the complex is massively influenced by the environment. In the solid state and in nonpolar solvents a paramagnetic, dinuclear Cu(II) complex with a neutral GFA ligand is present. In polar solvents, the electronic structure changes to a diamagnetic, dinuclear Cu(I) complex with a twofold-oxidized GFA ligand. Using acetone as a solvent, both electronic structures are accessible due to a temperature-dependent equilibrium between the two valence tautomeric complexes. Our results pave the way for a broader use of valence tautomeric transition-metal complexes in catalytic reactions since anionic coligands can now be tolerated owing to the neutral/positively charged GFA ligand.

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Section: Introductionmentioning

confidence: 99%

A Valence Tautomeric Dinuclear Copper Tetrakisguanidine Complex

Wiesner

Wagner

Kaifer

et al. 2016

Chemistry A European J

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“…The two bridging imido ligands occupy cis coordination sites on each metal leaving the sixth coordination site for the neutral toluidene donor ligand. There is a slight asymmetry in the imide TaÀN bond lengths, which are 2.0164(17) and 2.0349 (16) . The shorter distance corresponds to the TaÀN(imide) bond trans to the toluidene ligand, whereas the longer distance corresponds to the Ta À N(imide) bond trans to the amide nitrogen atom of the [ONO red ] 3À ligand.…”

mentioning

confidence: 99%

“…A key aspect to evaluate for the oxidation of 2 b is the role of the redox-active [ [16] X-ray-quality crystalline blocks of 5 were obtained from cold diethyl ether; the structure of 5 is presented as an ORTEP diagram in Figure 2. [8b]…”

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confidence: 99%

Four‐Electron Oxidative Formation of Aryl Diazenes Using a Tantalum Redox‐Active Ligand Complex

Zarkesh¹,

Ziller²,

Heyduk³

2008

Angew Chem Int Ed

150

121

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Transition-metal complexes capable of mediating multielectron transformations are critical components for a variety of small-molecule transformations. For example, the oxidation of CÀH bonds [1] and the reduction of protons to H 2 [2] are both two-electron transformations. The oxidation of water to O 2 is a four-electron process [3] and the reduction of nitrogen to ammonia is an overall six-electron process.[4] The design of metal complexes to promote or catalyze these multielectron reactions usually relies on one or more transition-metal ions capable of two-electron changes in a formal oxidation state. An alternative strategy is to incorporate redox-active ligands into the metal coordination sphere to supply reducing or oxidizing equivalents during a multielectron transformation.[5]Herein, we report the use of a tridentate redox-active ligand,, [6] coordinated to tantalum, to effect the fourelectron oxidative formation of aryl diazenes. In its reduced form, [ONO red ] 3À is a planar, tridentate ligand that coordinates to transition metals in a meridional geometry. The organometallic synthon TaMe 3 Cl 2 [7] has been used to prepare [ONO red ]TaMe 2 (1), which was then converted into the; 2 b, L = pyridine (py); Scheme 1). Oxidation of 2 b resulted in the quantitative elimination of (p-tolyl)N = N(ptolyl). To the best of our knowledge, this is the first example of N = N double bond formation and organic diazene elimination from a tantalum(V) bridging imido dimer. Oxidation studies of the related complex [ONO red ]TaCl 2 (4) with PhICl 2 suggest that the redox-active ligand plays the pivotal role of collecting oxidizing equivalents within the tantalum coordination sphere. The work presented herein highlights a new strategy for the design of metal complexes capable of multielectron oxidation reactions.The bridging imido complexes 2 a and 2 b were prepared via dimethyl complex 1 (Scheme 1). The methyl ligands of 1 are susceptible to protonolysis by anilines, which results in the formation of bimetallic complexes with two bridging imido ligands. As shown in Scheme 1, benzene solutions of 1 heated to reflux with two equivalents of NH 2 (p-tolyl) resulted in the formation of

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“…Further details concerning the electron transfer process occurring in cobalt-dioxolene complexes were obtained by the investigation of a complex formed by a Schiff base tridentate ligand [31][32][33] which may exist in five possible oxidation states, but it is usually found to coordinate as mononegative Cat-N-BQ or dinegative radical Cat-N-SQ (Scheme 2).…”

mentioning

confidence: 99%

“…31 It was found to undergo valence tautomeric interconversion in the solid state well above room temperature (Tc = 597 K). 32 However both electronic spectra and magnetic susceptibility measurements strongly suggest that in solution the valence tautomeric equilibrium occurs at room temperature. [ls-Co…”

mentioning

confidence: 99%

Optically induced valence tautomeric interconversion in cobalt dioxolene complexes

Beni¹,

Carbonera²,

Dei³

et al. 2006

J. Braz. Chem. Soc.

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A descoberta de que vários complexos de cobalto-dioxoleno exibem bi-estabilidade magnética foto induzida foi descrita recentemente. Este fenômeno encontra-se sempre associado a processos de interconversão de tautômeros de valência entre espécies de cobalto(III) baixo spin e de cobalto(II) alto spin. Enfatiza-se, nesta revisão, a forte correlação formal existente entre estes processos e o efeito LIESST (Light-Induced Excited Spin State Trapping) exibido por vários complexos de ferro(II) que sofrem interconversão de spin. A dinâmica da relaxação da espécie meta-estável fotoinduzida para o estado fundamental é discutida em termos de processos adiabáticos no âmbito da teoria de Jortner da relaxação multifônica sem radiação.The discovery that a number of cobalt-dioxolene complexes undergo photoswitchable behavior was reported in the recent past. This phenomenon is always associated with valence tautomeric interconversion processes involving low-spin cobalt(III) and high-spin cobalt(II) species. Herein is stressed the strong formal correlation existing between these processes and the LIESST (Light-Induced Excited Spin State Trapping) effect shown by several iron(II) complexes undergoing spin crossover interconversion. The dynamics of the relaxation of the photoinduced metastable species to the ground state is discussed in terms of non-adiabatic processes within the Jortner theory of radiationless multiphonon relaxation.

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Temperature-Induced Solid-State Valence Tautomeric Interconversion in Two Cobalt−Schiff Base Diquinone Complexes

Cited by 62 publications

References 42 publications

A Valence Tautomeric Dinuclear Copper Tetrakisguanidine Complex

A Valence Tautomeric Dinuclear Copper Tetrakisguanidine Complex

Four‐Electron Oxidative Formation of Aryl Diazenes Using a Tantalum Redox‐Active Ligand Complex

Optically induced valence tautomeric interconversion in cobalt dioxolene complexes

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