A Car-parrinello study of the formation of oxidizing intermediates from fenton's reagent in aqueous solution

摘要

This paper demonstrates the spontaneous formation of the much contested ferryl ion, Fe~(IV)O~(2+), in an aqueous solution of iron(II) and hydrogen peroxide by means of first principles molecular dynamics simulations. Starting from hydrogen peroxide coordinated to pentaaquairon(II) in water, we show that the oxygen-oxygen bond breaks spontaneously to form [(H_2O)_5Fe~(III)OH]~(2+) and a very short-lived OH~· radical. This radical abstracts immediately a hydrogen from a water ligand to form [(H_2O)_4Fe~(IV)(OH)_2]~(2+) and a water molecule. The hydrated ferryl ion [(H_2O)_5Fe~(IV)O]~(2+) is formed in a second step by proton donation from one OH ligand to the solvent. Starting from separated hydrogen peroxide and pentaaquairon(II) in water, we find a reactive pathway in which the ferryl ion is formed in a more direct way. As soon as H_2O_2 enters the iron(II) coordination shell, the oxygen-oxygen bond breaks and again an OH ligand and a short-lived OH~·radical is formed. The radical abstracts the hydrogen from the OH ligand to form again the ferryl ion.