Effect of anion-exchange resin on the formation of iron(III)-Tiron complexes

Abstract

A comparison between iron(III)-Tiron complexes in solution and in the presence of a finely divided anion-exchange resin suspension (ARS) was studied. The effects of the ARS on the acid dissociation constants of Tiron (K_a1 and K_a2) and on the stepwise stability constants (K₁, K₂ and K₃) of iron(III)-Tiron complexes (FeL, FeL₂ and FeL₃) were investigated. Instead of the three complexes formed in solution at different pH values, only two complexes (FeL₂ and FeL₃) were found to be fixed on the ARS. Although the ARS did not affect the acid dissociation constants of Tiron, the stability constants of FeL₂ and FeL₃ were considerably improved. The stepwise stability constants were 20.0, 18.5 and 15.0, respectively, compared with reported values in solution of 20.4, 15.1 and 10.8, respectively.