Ligand field, electronic and solvent effects in the non-aqueous electrochemistry of tris(β-dionato)chromium(III) chelates

Tsiamis, Chris; Hadjikostas, C.; Karageorgiou, Stephanos; Manoussakis, George

doi:10.1016/s0020-1693(00)85840-5

Cited by 14 publications

(3 citation statements)

References 34 publications

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“…Reaction 7) would consequently depend strongly on solvent choice, which could explain the widely variable reduction responses of Cr(acac) 3 observed in literature. [13][14][15][17][18][19][20] Studies of solvent compatibility for RFB applications similar to those performed earlier with V(acac) 3 41,42 could therefore be fruitful, and are ongoing.…”

Section: Spectroelectrochemistry Resultsmentioning

confidence: 85%

“…This would entail reducing a Cr[III] complex to Cr[I] while oxidizing another Cr[III] complex to Cr[VI], which is unlikely: examinations of the first reduction of Cr(acac) 3 on various electrodes and in various supporting solutions have not yielded any reports of multiple-electron first reductions. 13,15,[17][18][19][20] Additionally, a mechanism where the Cr[III] complex oxidized to Cr[VI] would be anomalous in light of the responses of other M(acac) 3 complexes, which appear consistent with single-electron oxidations. 2,9,28 Both dimerization of the complex or the chromium within it and ligand-dissociation processes allow mechanisms consistent with Equation 3 in which b/d = 2/3.…”

Section: A1241mentioning

confidence: 99%

“…[13][14][15][16][17] The literature describing nonaqueous Cr(acac) 3 electrochemistry does not provide a consensus about the mechanisms for either the first reduction or first oxidation of the neutral complex. The electrochemical response during reduction depends heavily upon solvent, with different behavior observed in dimethylsulfoxide, 13,15,18,19 N,N-dimethylformamide, 15 dichloromethane, 14 acetonitrile, 15,17,20 and others. 15 Various mechanisms have been proposed for the first reduction, but the first oxidation mechanism has only received significant attention since Cr(acac) 3 was proposed for nonaqueous RFB applications.…”

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Spectroelectrochemistry of Vanadium Acetylacetonate and Chromium Acetylacetonate for Symmetric Nonaqueous Flow Batteries

Saraidaridis

Bartlett

Monroe

2016

J. Electrochem. Soc.

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Chromium acetylacetonate, or Cr(acac) 3 , is a promising active species for high-energy-density symmetric redox flow batteries because the neutral complex supports multiple charge-transfer reactions with widely separated redox potentials. Voltammetric and spectroelectrochemical measurements were performed to probe the mechanism of the first electrochemical disproportionation of Cr(acac) 3 -i.e., the cell reaction associated with the two redox couples immediately adjacent to the equilibrium potential of a freshly prepared nonaqueous Cr(acac) 3 solution. Substantially different limiting currents are observed for the positive and negative half-reactions, suggesting that at least one deviates from the similar outer-sphere single-electron transfer mechanisms proposed earlier. Spectroelectrochemical chronoamperometry suggests ligand dissociation in the negative reaction, and consequent structural reorganization of the Cr(acac) 3 complex. Vanadium acetylacetonate was investigated for comparison, and no ligand dissociation was observed. A negative half-reaction mechanism consistent with the voltammetric and spectroelectrochemical data is proposed, and used to rationalize observations of charge/discharge behavior in cycling Cr (acac) As researchers have identified the economic benefits that largescale energy storage delivers to the grid, research into redox flow batteries (RFBs) has expanded.1 In efforts to increase energy density or decrease active-species loading, researchers have targeted nonaqueous RFB chemistries, which can produce operating potentials outside the stability window of water.2-8 Several nonaqueous chemistries are based on transition-metal-centered coordination complexes. 2,3,[6][7][8][9] Chromium acetylacetonate, or Cr(acac) 3 , appears especially promising as an RFB active species: it has five accessible redox states, and there is a wide voltage separation between the first reduced and first oxidized states of the neutral complex. The Cr(acac) 3 complex has also been used for catalysis 10 and as a standard for atomic absorption spectra.11 Whereas vanadium acetylacetonate, or V(acac) 3 , appears to support outer-sphere electron transfer for both single-electron addition and withdrawal in certain nonaqueous electrolytes, and to undergo both charge exchanges with relatively facile kinetics, 12 the voltammetric response of Cr(acac) 3 is harder to interpret. Experimental efforts to clarify the electrochemistry of Cr(acac) 3 have been challenging because the reaction mechanism apparently varies with the choices of solvent, supporting electrolyte, and working electrode. 13-17The literature describing nonaqueous Cr(acac) 3 electrochemistry does not provide a consensus about the mechanisms for either the first reduction or first oxidation of the neutral complex. The electrochemical response during reduction depends heavily upon solvent, with different behavior observed in dimethylsulfoxide, 13,15,18,19 N,N-dimethylformamide, 15 dichloromethane, 14 acetonitrile, 15,17,20 and others. 15 Various mechanisms have...

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Section: Spectroelectrochemistry Resultsmentioning

confidence: 85%

Section: A1241mentioning

confidence: 99%

mentioning

confidence: 99%

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Spectroelectrochemistry of Vanadium Acetylacetonate and Chromium Acetylacetonate for Symmetric Nonaqueous Flow Batteries

Saraidaridis

Bartlett

Monroe

2016

J. Electrochem. Soc.

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Redox Chemistry and Electrochemistry of Metal Enolates

Pampaloni

Zanello

2010

Patai's Chemistry of Functional Groups

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ChemInform Abstract: Ligand Field, Electronic and Solvent Effects in the Non‐Aqueous Electrochemistry of Tris(β‐dionato)chromium(III) Chelates.

Tsiamis¹,

Hadjikostas²,

Karageorgiou³

et al. 1988

ChemInform

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ChemInform Abstract The electrochemical behavior of a series of chelates (I) is investigated in acetonitrile and acetone. Reduction proceeds in one-electron steps involving the Cr ion. Solvent effects are less important than the influence of the substituents. Potentials range from -2.15 to -0.89 V and a linear correlation exists between E1/2 and the sum of Hammett σ functions of the substituents.

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Ligand field, electronic and solvent effects in the non-aqueous electrochemistry of tris(β-dionato)chromium(III) chelates

Cited by 14 publications

References 34 publications

Spectroelectrochemistry of Vanadium Acetylacetonate and Chromium Acetylacetonate for Symmetric Nonaqueous Flow Batteries

Spectroelectrochemistry of Vanadium Acetylacetonate and Chromium Acetylacetonate for Symmetric Nonaqueous Flow Batteries

Redox Chemistry and Electrochemistry of Metal Enolates

ChemInform Abstract: Ligand Field, Electronic and Solvent Effects in the Non‐Aqueous Electrochemistry of Tris(β‐dionato)chromium(III) Chelates.

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