title: Comparative study of electron transfer reactions at the ionic liquid/water and organic/water interfaces.
abstract: The rates of electron transfer (ET) reactions at the water/ionic liquid (IL) interface have been measured for the first time using scanning electrochemical microscopy. The standard bimolecular rate constant of the interfacial ET between ferrocene dissolved in 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and aqueous ferricyanide (0.4 M-1 cm s-1) was found to be approximately 30 times higher than the corresponding rate constant measured at the water/1,2-dichloroethane interface. The driving force dependence of the ET rate was investigated over a wide range of the interfacial potential drop values (>200 mV). The observed Butler-Volmer-type dependence is discussed in terms of the interfacial model. The ET was also probed at the interface between aqueous solution and the mixture of the IL and 1,2-dichloroethane. The mole fractions in this mixture were varied systematically to investigate the transition from the water/organic to the water/IL interface. The observed decrease in the rate constant with increasing mole fraction of 1,2-dichloroethane is in contrast with the previously reported direct correlation between the electrochemical rate constant and the diffusion coefficient of redox species in solution.
authors.affiliation: Department of Chemistry & Biochemistry, Queens College-CUNY, Flushing, New York 11367, USA.
authors.forename: François O
authors.initials: FO
authors.lastname: Laforge
authors.forename: Takashi
authors.initials: T
authors.lastname: Kakiuchi
authors.forename: Fumiko
authors.initials: F
authors.lastname: Shigematsu
authors.forename: Michael V
authors.initials: MV
authors.lastname: Mirkin