Ion pair formation and thermodynamic parameters of N-[(benzoyl-amino) thioxomethyl] histidine cobalt (II) chloride in water + methanol mixtures at different temperatures-A conductance study

The conductivities of N-[(benzoyl-amino) thioxomethyl]-histidine cobalt (II) chloride complex were measured in various methanol (M) + water (W) mixtures, i.e., Xmethanol = 0.0000-1.0000 at varying temperatures from 283.15 to 313.15K. The limiting molar conductance (Λ0) and the association constant (KA) were estimated by Shedlovsky technique for the electrolytes. The influence of the mixed solvent composition on the solvation of ions has been discussed based on the composition dependence of the Walden product (Λ0η0). Ion association constants calculated for the given complex salt in methanol-water mixtures increased, depending on the percentage of methanol. This was equivalent to the ion-association constants increasing with a decrease in the dielectric constant of the mixtures. Thermodynamic parameters (Gibb’s free energy, enthalpy, entropy and Arrhenius activation energy) were estimated from the temperature dependence of the ion- association constant. The results have been discussed in terms of ionion, ion-solvent and solvent-solvent interactions.

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