Effects of metal-counterion interactions on the percolation in microemulsions composed of bis(N-octylethylenediamine)metal(II) complexes in water/benzene and water/chloroform systems

Self-diffusions and electric conductivities of microemulsions composed of surfactant metal complexes, dianiono-bis(N-octylethylenediamine)zine(II) (aniono = chloro or nitrato), dichlorobis(N-octylethylenediamine)cadmium(II), and bis(N-octylethylenediamine) palladium(II) chloride ( = ZnCl2(oct-en)(2), Zn(NO3)(2)(oct-en)(2), CdCl2(oct-en)(2), and [Pd(oct-en)(2)]Cl-2, respectively) were studied in water/benzene or water/chloroform mixed solvent system. The electric conductivities of the solutions increase in the order, CdCl2(oct-en)(2) < ZnCl2(oct-en)(2) < Zn(NO3)(2)(oct-en)(2) [Pd(octen)(2)] systems. The profiles of the plots of the diffusion coefficients and of the electric conductivities versus water content depend on the ionicity of the metal-anion bond, i.e. in the [Pd(oct-en)(2)]Cl-2 and Zn(NO3)(2)(oct-en)(2) systems both the diffusion coefficients and the electric conductivities are positively dependent while for the other two systems the slopes of the plots are negative. Among them, it is characteristic that the electric conductivity versus water content plot for the palladium complex system shows a sharp peak at W-o (= [water]/[Pd complex]) = 43. These properties were explained on the basis of the pre-percolation phenomenon. (C) 2003 Elsevier Science B.V. All rights reserved.