Influence of Ligand Architecture in Tuning Reaction Bifurcation Pathways for Chlorite Oxidation by Non-Herne Iron Complexes

Prasenjit Barman, Abayomi S. Faponle, Anil Kumar Vardhaman, Davide Angelone, Anna-Maria Loehr, Wesley R. Browne, Peter Comba, Chivukula V. Sastri, Sam P. de Visser

Research output: Contribution to journalArticleAcademicpeer-review

11 Citations (Scopus)

Abstract

Reaction bifurcation processes are often encountered in the oxidation of substrates by enzymes and generally lead to a mixture of products. One particular bifurcation process that is common in biology relates to electron transfer versus oxygen atom transfer by high-valent iron(IV)-oxo complexes, which nature uses for the oxidation of metabolites and drugs. In biomimicry and bioremediation, an important reaction relates to the detoxification of ClOx- in water, which can lead to a mixture of products through bifurcated reactions. Herein we report the first three water-soluble non-heme iron(II) complexes that can generate chlorine dioxide from chlorite at ambient temperature and physiological pH. These complexes are highly active oxygenation oxidants and convert ClO2- into either ClO2 or ClO3- via high-valent iron(IV)-oxo intermediates. We characterize the short-lived iron(IV)-oxo species and establish rate constants for the bifurcation mechanism leading to ClO2 and ClO3- products. We show that the ligand architecture of the metal center plays a dominant role by lowering the reduction potential of the metal center. Our experiments are supported by computational modeling, and a predictive valence bond model highlights the various factors relating to the substrate and oxidant that determine the bifurcation pathway and explains the origins of the product distributions. Our combined kinetic, spectroscopic, and computational studies reveal the key components necessary for the future development of efficient chlorite oxidation catalysts.

Original languageEnglish
Pages (from-to)10170-10181
Number of pages12
JournalInorganic Chemistry
Volume55
Issue number20
DOIs
Publication statusPublished - 17-Oct-2016

Keywords

  • COUPLED ELECTRON-TRANSFER
  • NONHEME IRON(IV)-OXO
  • VALENCE-BOND
  • CYTOCHROME-P450 ENZYMES
  • SUBSTRATE HYDROXYLATION
  • CORRELATION-ENERGY
  • OXYGEN-BINDING
  • OXO COMPLEXES
  • MECHANISM
  • HEME

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