Novel features associated with the electrochemically driven bis(η5-pentaphenylcyclopentadienyl)iron(II)-iron(III) redox transformation at an electrode-microcrystal-solvent (electrolyte) interface

Alan M. Bond; Axel Lamprecht; Vanda Tedesco; Frank Marken

Novel features associated with the electrochemically driven bis(η⁵-pentaphenylcyclopentadienyl)iron(II)-iron(III) redox transformation at an electrode-microcrystal-solvent (electrolyte) interface

Alan M. Bond, Axel Lamprecht, Vanda Tedesco, Frank Marken

Research output: Contribution to journal › Article › peer-review

9 Citations (SciVal)

Abstract

Electrochemical oxidation of microcrystals of the iron(II) compound, Fe(η⁵-C₅Ph₅)₂ and reduction of the corresponding iron(III) [Fe(η⁵-C₅Ph₅)₂]BF₄ salt, mechanically attached to graphite and gold electrodes placed in aqueous media and in a (70:30) water:acetonitrile solvent mixture containing electrolyte has been investigated by voltammetric, electrochemical quartz crystal microbalance, and micro-analytical techniques. When interconversion of Fe(η⁵-C₅Ph₅)₂ to [Fe(η⁵-C₅Ph₅)₂]X (X^-=ClO₄^-, BF₄^-, Cl^-, F^-) and vice versa occurs at the microcrystal-electrode-aqueous electrolyte interface via redox cycling of the electrode potential, then the reaction can be summarised by the process[Fe(η⁵-C₅Ph₅)₂] ⁺[X^-]_(solid)+e^-⇌Fe(η ⁵-C₅Ph₅)_2(solid)+X^- _(solution)However, when CH₃CN (in aqueous 0.1 M NaClO₄) is present at the interface, data obtained are consistent with co-insertion of the organic solvent into the structure to give formally the [Fe(η⁵-C₅Ph₅)₂] ^1+/0.5+/0_(solid) redox system containing interacting iron atoms in the solid structure. The formation of the new phase is voltammetrically associated with the conversion from the single chemically reversible one electron [Fe(η⁵-C₅Ph₅)₂]^+/0 process with a large separation in reduction and oxidation peak potentials (E_p^red=385 mV, E_p^ox=980 mV) to two formally 0.5 electron processes with more closely spaced peak potentials (first 0.5 electron reduction: E_p^red=665 mV, E_p^ox=715 mV; second 0.5 electron reduction: E_p^red=545 mV, E_p^ox=610 mV). Mechanistic aspects of the substantial changes that are introduced by the incorporation of acetonitrile into the solid state structure are discussed.

Original language	English
Pages (from-to)	21-31
Number of pages	11
Journal	Inorganica Chimica Acta
Volume	291
Issue number	1-2
Publication status	Published - 1 Aug 1999

Funding

The authors express their appreciation to the research groups of A.F. Masters and H. Schumann for their generous donation of samples of Fe(η 5 -C 5 Ph 5 ) 2 and [Fe(η 5 -C 5 Ph 5 ) 2 ]BF 4 . Financial support from Ciba–Geigy Jubiläumsstiftung and the Australian Research Council also are gratefully acknowledged. F.M. thanks the Royal Society for the award of a University Research Fellowship and New College (Oxford) for a Stipendiary Lectureship.

Keywords

Cyclopentadienyl complexes
Electrochemistry
Iron complexes

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Inorganic Chemistry
Materials Chemistry

Cite this

Novel features associated with the electrochemically driven bis(η⁵-pentaphenylcyclopentadienyl)iron(II)-iron(III) redox transformation at an electrode-microcrystal-solvent (electrolyte) interface. / Bond, Alan M.; Lamprecht, Axel; Tedesco, Vanda et al.
In: Inorganica Chimica Acta, Vol. 291, No. 1-2, 01.08.1999, p. 21-31.

Research output: Contribution to journal › Article › peer-review

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title = "Novel features associated with the electrochemically driven bis(η5-pentaphenylcyclopentadienyl)iron(II)-iron(III) redox transformation at an electrode-microcrystal-solvent (electrolyte) interface",

abstract = "Electrochemical oxidation of microcrystals of the iron(II) compound, Fe(η5-C5Ph5)2 and reduction of the corresponding iron(III) [Fe(η5-C5Ph5)2]BF4 salt, mechanically attached to graphite and gold electrodes placed in aqueous media and in a (70:30) water:acetonitrile solvent mixture containing electrolyte has been investigated by voltammetric, electrochemical quartz crystal microbalance, and micro-analytical techniques. When interconversion of Fe(η5-C5Ph5)2 to [Fe(η5-C5Ph5)2]X (X-=ClO4-, BF4-, Cl-, F-) and vice versa occurs at the microcrystal-electrode-aqueous electrolyte interface via redox cycling of the electrode potential, then the reaction can be summarised by the process[Fe(η5-C5Ph5)2] +[X-](solid)+e-⇌Fe(η 5-C5Ph5)2(solid)+X- (solution)However, when CH3CN (in aqueous 0.1 M NaClO4) is present at the interface, data obtained are consistent with co-insertion of the organic solvent into the structure to give formally the [Fe(η5-C5Ph5)2] 1+/0.5+/0(solid) redox system containing interacting iron atoms in the solid structure. The formation of the new phase is voltammetrically associated with the conversion from the single chemically reversible one electron [Fe(η5-C5Ph5)2]+/0 process with a large separation in reduction and oxidation peak potentials (Epred=385 mV, Epox=980 mV) to two formally 0.5 electron processes with more closely spaced peak potentials (first 0.5 electron reduction: Epred=665 mV, Epox=715 mV; second 0.5 electron reduction: Epred=545 mV, Epox=610 mV). Mechanistic aspects of the substantial changes that are introduced by the incorporation of acetonitrile into the solid state structure are discussed.",

keywords = "Cyclopentadienyl complexes, Electrochemistry, Iron complexes",

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N2 - Electrochemical oxidation of microcrystals of the iron(II) compound, Fe(η5-C5Ph5)2 and reduction of the corresponding iron(III) [Fe(η5-C5Ph5)2]BF4 salt, mechanically attached to graphite and gold electrodes placed in aqueous media and in a (70:30) water:acetonitrile solvent mixture containing electrolyte has been investigated by voltammetric, electrochemical quartz crystal microbalance, and micro-analytical techniques. When interconversion of Fe(η5-C5Ph5)2 to [Fe(η5-C5Ph5)2]X (X-=ClO4-, BF4-, Cl-, F-) and vice versa occurs at the microcrystal-electrode-aqueous electrolyte interface via redox cycling of the electrode potential, then the reaction can be summarised by the process[Fe(η5-C5Ph5)2] +[X-](solid)+e-⇌Fe(η 5-C5Ph5)2(solid)+X- (solution)However, when CH3CN (in aqueous 0.1 M NaClO4) is present at the interface, data obtained are consistent with co-insertion of the organic solvent into the structure to give formally the [Fe(η5-C5Ph5)2] 1+/0.5+/0(solid) redox system containing interacting iron atoms in the solid structure. The formation of the new phase is voltammetrically associated with the conversion from the single chemically reversible one electron [Fe(η5-C5Ph5)2]+/0 process with a large separation in reduction and oxidation peak potentials (Epred=385 mV, Epox=980 mV) to two formally 0.5 electron processes with more closely spaced peak potentials (first 0.5 electron reduction: Epred=665 mV, Epox=715 mV; second 0.5 electron reduction: Epred=545 mV, Epox=610 mV). Mechanistic aspects of the substantial changes that are introduced by the incorporation of acetonitrile into the solid state structure are discussed.

AB - Electrochemical oxidation of microcrystals of the iron(II) compound, Fe(η5-C5Ph5)2 and reduction of the corresponding iron(III) [Fe(η5-C5Ph5)2]BF4 salt, mechanically attached to graphite and gold electrodes placed in aqueous media and in a (70:30) water:acetonitrile solvent mixture containing electrolyte has been investigated by voltammetric, electrochemical quartz crystal microbalance, and micro-analytical techniques. When interconversion of Fe(η5-C5Ph5)2 to [Fe(η5-C5Ph5)2]X (X-=ClO4-, BF4-, Cl-, F-) and vice versa occurs at the microcrystal-electrode-aqueous electrolyte interface via redox cycling of the electrode potential, then the reaction can be summarised by the process[Fe(η5-C5Ph5)2] +[X-](solid)+e-⇌Fe(η 5-C5Ph5)2(solid)+X- (solution)However, when CH3CN (in aqueous 0.1 M NaClO4) is present at the interface, data obtained are consistent with co-insertion of the organic solvent into the structure to give formally the [Fe(η5-C5Ph5)2] 1+/0.5+/0(solid) redox system containing interacting iron atoms in the solid structure. The formation of the new phase is voltammetrically associated with the conversion from the single chemically reversible one electron [Fe(η5-C5Ph5)2]+/0 process with a large separation in reduction and oxidation peak potentials (Epred=385 mV, Epox=980 mV) to two formally 0.5 electron processes with more closely spaced peak potentials (first 0.5 electron reduction: Epred=665 mV, Epox=715 mV; second 0.5 electron reduction: Epred=545 mV, Epox=610 mV). Mechanistic aspects of the substantial changes that are introduced by the incorporation of acetonitrile into the solid state structure are discussed.

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