Kinetics of Reduction of Some Surfactant-Cobalt(III) Complexes by Iron(II)

Abstract

The electron transfer kinetics of the reaction between the surfactant-cobalt(III) complex ions, cis-[Co(en) 2 (C 12 H 25 NH 2 ) 2 ] 3þ , cis-a-[Co(trien)(C 12 H 25 NH 2 ) 2 ] 3þ (en:ethylenediamine, trien: triethylenetetramine, C 12 H 25 NH 2 : dodecylamine) by iron(II) in aqueous solution was studied at 298, 303, 308 K by spectrophotometry method under pseudo-first-order conditions using an excess of the reductant in self-micelles formed by the oxidant, cobalt(III) complex molecules, themselves. The rate constant of the electron transfer reaction depends on the initial concentration of the surfactant cobalt(III) complexes. DS # also varies with initial concentration of the surfactant cobalt(III) complexes. By assuming outer-sphere mechanism, the results have been explained based on the presence of aggregated structures containing cobalt(III) complexes at the surface of the self-micelles formed by the surfactant cobalt(III) complexes in the reaction medium. The rate constant of each complex increases with initial concentration of one of the reactants surfactant-cobalt(III) complex, which shows that self micelles formed by surfactantcobalt(III) complex itself has much influence on these reactions. The electron transfer reaction of the surfactant-cobalt(III) complexes was also carried out in a medium of various concentrations of b-cyclodextrin. b-cyclodextrin retarded the rate of the reaction.