Perturbations of the Briggs–Rauscher oscillating system by iron–phenanthroline complexes

Perturbations of the oscillatory regime of the Briggs–Rauscher (BR) reaction by the iron(II)–phenanthroline (ferroin) complex were observed in batch conditions. The path of the perturbation (immediate quenching of oscillations – inhibition time – resumption of oscillations) is similar to that provoked by antioxidant free-radical scavengers; however, perturbations occur in a ferroin concentration range much lower than that in which antioxidants act. To investigate this effect, reactions between the iron(II)–or iron(III)–phenanthroline (ferriin) and reagents or intermediates of the BR system were studied in detail. Results of these studies showed that the interaction of the ferroin/ferriin couple with iodine production is responsible for the observed perturbation. A mechanistic interpretation involving HOOradical dot radical is proposed.