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

Abstract

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.

Periodate-Mediated Aerobic Oxidation of Sulfides over a Bifunctional Porphyrin-polyoxometalate Catalyst: Photosensitized Singlet Oxygen Oxidation of Iodate to Periodate

“…Most terminal oxidants used in biomimetic oxidation of organic compounds are consumed in stoichiometrically equivalent amounts. − ,− Regeneration of the reduced terminal oxidant by molecular oxygen is a green chemistry strategy for the replacement of chemical terminal oxidants with air as the most abundant, sustainable, and greenest oxidant. Photosensitized regeneration of the reagents consumed in chemical and biological transformations is an efficient approach to achieve this goal.…”

“…Over the past decades, different reagents such as molecular oxygen, , hydrogen peroxide, , alkyl hydroperoxides, , peracids, , hypervalent iodine compounds, , oxone, , hypochlorite, , and amine oxides , have been used as the terminal oxidants for metal-catalyzed oxidation of organic compounds. Transfer of oxygen from metal-coordinated ligands such as nitro group to an organic substrate, followed by the metal-catalyzed regeneration of the oxidant by molecular oxygen, has been reported as a new approach for the activation of electrophilic oxygens by Tovrog et al in 1979.…”

Stimuli‐Responsive Organic Near‐Infrared Photoacoustic Probes

“…Endogenous ClO − is helpful for the immune system of organisms. [ 43 ] However, ClO − concentration disorders can cause various diseases, such as lung injury, [ 44 ] cardiovascular diseases, [ 45 ] inflammation, [ 46 ] and cancers. [ 47 ] Pu et al explored an amphiphile SOA‐based nanoprobe for the in vivo visualization of ClO − via ratiometric PA imaging ( Figure a).…”

Probing Noncovalent Interactions in [3,3]Metaparacyclophanes

“…Noncovalent interactions involving aromatic rings play important roles in diverse chemical and biological processes. , Arene–arene interactions contribute to the stabilization of the structure of macromolecules, supramolecular structures, molecular recognition processes, organic solar cells, and catalyst design. − The analysis of protein structures indicated that, on average, about 60% of aromatic side chains in proteins are involved in aromatic pairs, and about 80% form three or more interacting aromatic side chains . T-shaped and parallel-displaced geometries are the preferred orientations, whereas cofacial parallel geometry is rarely observed in proteins .…”