Cooperative Co-Activation of Water and Hypochlorite by a Non-Heme Diiron(III) Complex

James N. McPherson, Christopher J. Miller, Christina Wegeberg, Yingyue Chang, Erik Donovan Hedegård, Eckhard Bill, T. David Waite, Christine J. McKenzie*

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Abstrakt

Aqueous solutions of the iron(III) complex of N,N,N′-tris(2-pyridylmethyl)ethylenediamine-N′-acetate (tpena) react with hypochlorite (ClO-) to produce the reactive high-valent [FeIV(O)(tpena)]+. Under catalytic conditions, in bicarbonate-buffered media (pH 8) with a set ionic strength (10 mM NaCl), kinetic analysis shows that two equivalents of [FeIV(O)(tpena)]+ per one ClO- are produced, with benign chloride ions the only byproduct. An unprecedented supramolecular activation of ClO- by {(HCO3)⊂[(tpena)FeIII(μ-O)FeIII(Htpena)]}2+ is proposed. This mode of activation has great advantage for use in the catalytic oxidation of C-H bonds in water since: (i) the catalyst scaffold is protected from oxidative degradation and (ii) undesirable radical side reactions which produce toxic chlorinated compounds are circumvented by this novel coactivation of water and ClO-. The unique activation mechanism by the Fe-tpena system makes possible the destruction of organic contaminants as an add-on technology to water disinfection by chlorination, demonstrated here through (i) the catalytic oxidation of micropollutant metaldehyde, and (ii) mineralization of the model substrate formate. The resting-state speciation at pH 3, 5, 7, and 9, as well as the catalytically active iron speciation are characterized with Mössbauer and EPR spectroscopy and supported by DFT calculations. Our study provides fundamentally new insights into the design and activation mode of iron-based catalysts relevant to applications in water remediation.

OriginalsprogEngelsk
TidsskriftJournal of the American Chemical Society
Vol/bind143
Udgave nummer37
Sider (fra-til)15400–15412
ISSN0002-7863
DOI
StatusUdgivet - 2021

Bibliografisk note

Funding Information:
This work was supported by the Danish Council for Independent Research|Technology and Production (Grant No. 9041-00170B to C.J.M.), Independent Research Fund Denmark (Grant No. 0252-00002B to E.D.H.), The Villum Foundation, Young Investigator Program (grant no. 29412 to EDH), and the Australian Research Council (Grant No. DP190103375 to T.D.W.) and the Max Planck Society.

Publisher Copyright:
© 2021 American Chemical Society.

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