Solvent effects on the redox properties of tris-(1,10-phenanthroline)iron(II/III) complexes

Mayer, U.; Kotočová, A.; Gutmann, V.

doi:10.1016/s0022-0728(79)80364-2

Cited by 18 publications

(9 citation statements)

References 17 publications

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“…The redox reaction between divalent and trivalent tris(phen)iron complexes has been widely studied in aqueous and organic electrolytes. [13][14][15][16] The redox reactions of divalent and trivalent tris(phen)iron has been also investigated in an ionic liquid, 1-butyl-3-methylimidazolium (BMI + ) bis(trifluoromethylsulfonyl)amide (TFSA − ). 17 Since phen is larger in size than bpy (Fig.…”

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confidence: 99%

Electrochemical Reaction of Tris(1,10-phenanthroline)iron Complexes in Some Amide-Type Ionic Liquids

Katayama

Yoshihara

Miura

2015

J. Electrochem. Soc.

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Electrode reactions of tris(1,10-phenanthroline)iron complexes, [Fe(phen) 3 ] 3+/2+ , were investigated in some amide-type ionic liquids. The diffusion coefficients of [Fe(phen) 3 ] 2+ and [Fe(phen) 3 ] 3+ were smaller than those of tris(2,2 -bipyridine)iron complexes, [Fe(bpy) 3 ] 2+ and [Fe(bpy) 3 ] 3+ , in each ionic liquid, reflecting the phen complexes are larger than the bpy complexes. The ratio of diffusion coefficient of the trivalent species to that of the divalent one for [Fe(phen) 3 ] 3+/2+ was smaller than that for [Fe(bpy) 3 ] 3+/2+ , indicating the coulombic interaction between the charged species and the ions composing the ionic liquid is dependent on the charge densities of complexes. The rate constants for [Fe(phen) Electrochemical behavior of metal complexes in ionic liquids have been known to depend on the physicochemical properties of the ionic liquids.1-5 Since ionic liquids are composed of only cations and anions without any neutral molecule, the coulombic interaction between a charged species and the ions composing ionic liquids is significant compared with conventional aqueous or organic electrolyte solutions. Diffusion of a species in the conventional solutions is often represented by Stokes-Einstein relation, which is derived simply from the balance between the thermodynamic force based on the activity gradient of the species and the frictional force depending on the size of the species and the viscosity of the solution. However, Stokes-Einstein relation is inaccurate for a charged species even in conventional solutions. For polar solvents, modification of Stokes-Einstein relation has been proposed by considering dielectric friction in addition to the viscous drag.6,7 It has been known that the diffusion of a charged species dissolved in ionic liquids is affected not only by the viscosity of ionic liquids but also by the coulombic interaction between the charged species and the ions composing the ionic liquids, 1,2,4,5 suggesting Stokes-Einstein relation also needs some modification for the charged species diffusing in the ionic liquids. The charge transfer rate of the outer-sphere electron transfer complex is also known to be influenced by the physicochemical properties of the media. 8 The frequency factor of rate constant depends on the solvent dynamics, which is closely related to the viscosity of the medium. The activation Gibbs energy is given by the reorganization energy, which is composed of the inner and outer components. Although the inner component related to the bonds between the center metal and the ligands is insensitive to the medium, the outer component is dependent on the interaction between the complex and the medium. In conventional solutions, the outer component of reorganization energy is mainly determined by the dielectric interaction. However, the contribution of the coulombic interaction to the outer component is expected to be dominant in ionic liquids. Furthermore, the reaction entropy of the redox complexes without the change of their coordi...

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confidence: 99%

Electrochemical Reaction of Tris(1,10-phenanthroline)iron Complexes in Some Amide-Type Ionic Liquids

Katayama

Yoshihara

Miura

2015

J. Electrochem. Soc.

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“…1), have been regarded as typical outer-sphere electron transfer reactions in various solutions. [3][4][5][6][7][8][9][10][11][12] While it is possible to assume the size of complexes to be constant regardless of their oxidation states, the complexes can take variety of electric charges from −1 to +3 due to the electron transfer not only in the ruthenium metal center but also in bpy ligands. Thus, tris(bpy)ruthenium complexes can be used as an ideal probe for investigating the interaction of the complexes with the species surrounding them.…”

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Electrode Kinetics of Tris(2,2^′-bipyridine)ruthenium Complexes in 1-Ethyl-3-methylimidazolium Tetrafluoroborate Ionic Liquid

Katayama¹,

Toshimitsu²,

Miura³

2013

J. Electrochem. Soc.

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The electrode reaction of tris(2,2′-bipyridine)ruthenium complexes ([Ru(bpy)3]n+, n = 2 and 3) has been investigated in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI[BF4]) ionic liquid. The formal potential of [Ru(bpy)3]3+/2+ couple was 0.85 V vs. ferrocene/ferrocenium at 25°C. The diffusion coefficients of [Ru(bpy)3]2+ and [Ru(bpy)3]3+ were (7.8 ± 0.1) × 10−8 and (3.3 ± 0.1) × 10−8 cm2 s−1, respectively, at 25°C. The diffusion coefficients in EMI[BF4] were smaller than those reported in EMITFSA (TFSA− = bis(trifluoromethylsulfonyl)amide), of which the viscosity is close to that of EMI[BF4]. In addition, the ratio of the diffusion coefficient of [Ru(bpy)3]2+ to that of [Ru(bpy)3]3+ in EMI[BF4] was smaller than that in EMITFSA, indicating the diffusivity of the cationic species is strongly affected by the charge density of the anion of ionic liquids. The rate constant for [Ru(bpy)3]3+/2+ couple at 25°C was (6.7 ± 0.2) × 10−5 cm s−1, which was smaller by two orders of magnitude than that in EMITFSA, suggesting the difference in the charge densities between [BF4]− and TFSA− also affects the outer-sphere component of reorganizing energy of the complexes.

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“…3 According to the speciation distribution diagrams of Fe(II)-and Fe(III)-edta complexes (abbreviated as Fe(II,III)-edta) in aqueous solution, the redox potential of Fe(II,III)-edta is dependent on pH, i.e., it is more positive than 0 mV in a low pH region 22 and about ¹150 mV at pH 4.5 (vs. Ag/AgCl). 21 Taking account of intrinsically Electrochemistry, 83(9), 730-732 (2015) acidic character of betainium 26 and other effects, such as the liquid junction potential or donor properties of the solvent molecule, 27 it is plausible that E 1 0 is 146 mV in [Hbet][Tf 2 N]/11 wt%H 2 O system. As mentioned above, the current peak P a2 in Fig.…”

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confidence: 99%

Studies on Metal Complexes as Active Materials in Redox-flow Battery Using Ionic Liquids as Electrolyte: Cyclic Voltammetry of Betainium Bis(Trifluoromethylsulfonyl)Imide Solution Dissolving Na[Fe<sup>III</sup>(edta)(H<sub>2</sub>O)] as an Anode Active Material

2015

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Solvent effects on the redox properties of tris-(1,10-phenanthroline)iron(II/III) complexes

Cited by 18 publications

References 17 publications

Electrochemical Reaction of Tris(1,10-phenanthroline)iron Complexes in Some Amide-Type Ionic Liquids

Electrochemical Reaction of Tris(1,10-phenanthroline)iron Complexes in Some Amide-Type Ionic Liquids

Electrode Kinetics of Tris(2,2^′-bipyridine)ruthenium Complexes in 1-Ethyl-3-methylimidazolium Tetrafluoroborate Ionic Liquid

Studies on Metal Complexes as Active Materials in Redox-flow Battery Using Ionic Liquids as Electrolyte: Cyclic Voltammetry of Betainium Bis(Trifluoromethylsulfonyl)Imide Solution Dissolving Na[Fe<sup>III</sup>(edta)(H<sub>2</sub>O)] as an Anode Active Material

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Solvent effects on the redox properties of tris-(1,10-phenanthroline)iron(II/III) complexes

Cited by 18 publications

References 17 publications

Electrochemical Reaction of Tris(1,10-phenanthroline)iron Complexes in Some Amide-Type Ionic Liquids

Electrochemical Reaction of Tris(1,10-phenanthroline)iron Complexes in Some Amide-Type Ionic Liquids

Electrode Kinetics of Tris(2,2′-bipyridine)ruthenium Complexes in 1-Ethyl-3-methylimidazolium Tetrafluoroborate Ionic Liquid

Studies on Metal Complexes as Active Materials in Redox-flow Battery Using Ionic Liquids as Electrolyte: Cyclic Voltammetry of Betainium Bis(Trifluoromethylsulfonyl)Imide Solution Dissolving Na[Fe<sup>III</sup>(edta)(H<sub>2</sub>O)] as an Anode Active Material

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Electrode Kinetics of Tris(2,2^′-bipyridine)ruthenium Complexes in 1-Ethyl-3-methylimidazolium Tetrafluoroborate Ionic Liquid