Differential Refractometric Studies on Some Strong and Weak Molecular Complexes

Article abstract of DOI:10.1246/bcsj.53.2995

A more adequate model has been developed to determine the equilibrium constant (K₁) and stoichiometry of molecular complexes.This model involves the assumption: , where ΔΦ_a is the difference in refraction per cm³ of solution and acceptor; ΔΦ_d is the difference in the refraction per cm³ of solution and donor; α is the extent of electronic polarization.C⁰_Λ and C⁰_D are the initial concentrations of acceptor and donor respectively.This model has been verified on some strong and weak complexes and was found better than that of earlier methods. ΔΦ_a, ΔΦ_d, and ΔΩC_DA (refraction per cm³ due to charge-transfer complex) have also been used to Yoshida and Osawa's method.The K₁ obtained from the plot of ΔΦ_a or ΔΦ_d versus molar ratio of solutes were found more reliable for weak complexes than K₁ calculated from Yoshida and Osawa's plot.From these plots the percentage of contribution of donor or acceptor in total 30percent solute aggregation as proposed by Yoshida and Osawa has been calculated.It is also noted that Yoshida and Osawa's method may give the reliable value for strong complexes but for weak complexes only differential refractometric method can provide the best values.