Kinetics of Dissociation of bis(2,4,6-Tripyridyl-s-triazine)iron(II) and tris(2,2′-Bipyridyl)iron(II) in the presence of Triton X-100/Tween 80 Mixed Micellar Medium

Abstract

Surface tension studies were carried on the binary surfactant mixtures over a wide range of Triton X-100 mole fractions and total surfactant concentrations to obtain critical micellar concentration values. These values were used to determine the composition of the mixed micelles and the average interaction parameter (β) which contains all the interactions of the mixed surfactants. The method is based on Rubingh′s theory using a Gauss-Newton iteration technique written in FORTRAN. The value of β was found to be -0.69 indicating synergistic behaviour i.e., combined positive catalytic effect of both the surfactants on rates of reactions. Hence, the kinetics of dissociation of bis(2,4,6-tripyridyl-striazine) iron(II) ([Fe(tptz)2]2+) and tris(2,2′-bipyridyl)iron(II) ([Fe(bipy)3]2+) were studied in the presence of Triton X-100/Tween 80 mixed micellar medium. The reactions have been carried out in the presence of mixed micelles of Triton X-100/Tween 80 at various mole fractions of Triton X-100 (αTX-100 = [Triton X-100]/([Triton X-100] + [Tween 80])) and at different total surfactant concentrations of Triton X-100 and Tween 80 (Ct = [Triton X-100] + [Tween 80]). The results show that as αTX-100 increases the rate increases for all values of Ct. Kinetic analysis has been carried out by using a simple pseudo phase model and binding constants were determined. These binding constants were found to be in agreement with the binding constants obtained spectrophotometrically.