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Abstract: The electron transfer reaction between bis(phthalocyaninato)lutetium(III) ([Lu(pc)2]0) in 1,2-dichloroethane (1,2-DCE) and hexacyanoferrate(II/III) redox couple ([Fe(CN)6]4−/3−) in water (W) at the interface was studied by the use of normal pulse voltammetry and ac-voltammetry. The ac-voltammetric results have reconfirmed that the electron transfer reaction between [Lu(pc)2] in 1,2-DCE and [Fe(CN)6]4−/3− in W takes place by way of the heterogeneous electron transfer at the interface, but not by the homogeneous electron transfer reaction associated with the ion transfer of redox species across the interface. The kinetic parameters of the heterogeneous electron transfer reaction at the interface were determined. [Copyright &y& Elsevier]

Abstract: The electron transfer (ET) reaction between bis(cyclopentadienyl)iron(II) ([FeII(C5H5)2]) in 1,2-dichloroethane (1,2-DCE) and in nitrobenzene (NB) and hexacyanoferrate redox couple ([FeII/III(CN)6]4−/3−) in water (W) at the interface has been studied by use of normal-pulse voltammetry. The voltammetric results indicate that the ET reaction between [FeII(C5H5)2] in O (O=1,2-DCE or NB) and [FeII/III(CN)6]4−/3− in W takes place not by way of the heterogeneous ET at O|W interface but by the mechanism in which a homogeneous ET reaction between [FeII(C5H5)2] (partially distributed from O) and [FeIII(CN)6]3− takes place in W phase and the resultant [FeIII(C5H5)2]+ ion is responsible for the current passage across the interface. From the limiting current, the forward rate constants of the homogeneous ET reaction: [Fe(C5H5)2]+[Fe(CN)6]3− =[Fe(C5H5)2]+ +[Fe(CN)6]4− in W phase, , were determined to be (3.2±2.0)×1010 M−1 s−1 and (2.0±1.3)×1010 M−1 s−1 with the 1,2-DCE|W (1.5M Li2SO4) and NB|W (1.5M Li2SO4) interfaces, respectively. These values are in the order of the rate constant of diffusion-controlled bimolecular reaction in solution. Also, the formal (standard) potentials of the transfer of [Fe(C5H5)2]+ ion at the interface, , were determined to be −0.015±0.014V and −0.087±0.015V with the 1,2-DCE|W (1.5M Li2SO4) and NB|W (1.5M Li2SO4) interfaces, respectively. [Copyright &y& Elsevier]

Abstract: The electron transfer (ET) reaction between bis(butylcyclopentadienyl)iron(II) ([FeII(C5H4Bu)2]) in 1,2-dichloroethane (1,2-DCE) and the hexacyanoferrate redox couple ([FeII/III(CN)6]4−/3−) in water (W) at the 1,2-DCE∣W interface has been studied by use of normal pulse voltammetry and cyclic voltammetry. In normal pulse voltammetry, S-shaped current vs. potential curves with well-defined limiting currents attributable to the interfacial ET reaction were observed. The voltammetric results can be explained well by the theoretical equations [M. Senda, Rev. Polarogr. (Jpn), 49 (2003) 219; 50 (2004) 60] according to a so-called IT-mechanism, that is, the [FeII(C5H4Bu)2] molecule is transferred from the 1,2-DCE to the W phase across the interface, then the ET reaction takes place homogeneously in the W phase between [FeIII(CN)6]3−(W) and [FeII(C5H4Bu)2](W) to produce [FeII(CN)6]4−(W) and [FeIII(C5H4Bu)2]+(W), which is followed by the transfer of the [FeIII(C5H4Bu)2]+ ion from the W to the 1,2-DCE phase across the interface to give the voltammetric current. Experimental results from cyclic voltammetry are also explained well by the IT-mechanism. [Copyright &y& Elsevier]

The electron transfer reaction across the 1,6-dichlorohexane (1,6-DCH)|water (W) interface where bis(pentamethylcyclopentadienyl)iron(II/III) ([FeII/III(C5Me5)2]0/+) as the organic redox couple in 1,6-DCH is present in excess has been studied by cyclic voltammetry. The 1,6-DCH|W interface gave a potential window where the transfer of [FeIII(C5Me5)2]+ ion as well as that of [FeII(C5Me5)2]0 across the interface can be neglected. When hexaammineruthenium(III) and cyano complexes of iron protoporphyrin IX and microperoxidase-11, which do not transfer across the 1,6-DCH|W interface in the potential range tested, are present in W as the aqueous reactant, well-defined voltammetric waves due to the heterogeneous electron transfer have been observed within the potential window. The voltammetric waves can be assigned to reversible one-electron transfer controlled by diffusion of the aqueous redox couple in W. The reversible half-wave potentials are consistent with those predicted from simple voltammetric experiments with a Pt electrode. [Copyright &y& Elsevier]