Bioinspired Dismutation of Chlorite to Dioxygen and Chloride Catalyzed by a Water‐Soluble Iron Porphyrin

Zdilla, Michael J.; Lee, Amanda Q.; Abu‐Omar, Mahdi M.

doi:10.1002/anie.200801521

Cited by 37 publications

(22 citation statements)

References 23 publications

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“…In contrast to the iron(III) [Fe III (TF 4 TMAP)] 5+ catalyzed reaction [13,14], the analogous manganese complex investigated herein does not produce dioxygen. Instead chlorine dioxide (ClO 2 ) is formed with accumulation of Mn IV (O) at pH 6.90.…”

Section: Resultscontrasting

confidence: 57%

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Mechanistic study of a manganese porphyrin catalyst for on-demand production of chlorine dioxide in water

Hicks

Xiong

Bougher

et al. 2015

J. Porphyrins Phthalocyanines

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A water-soluble manganese porphyrin complex was examined for the catalytic formation of chlorine dioxide from chlorite under ambient temperature at pH 5.00 and 6.90. Quantitative kinetic modeling allowed for the deduction of a mechanism that accounts for all experimental observations. Catalysis is initiated via an OAT (Oxygen Atom Transfer) reaction resulting in formation of a putative manganese(V) oxo species, which undergoes ET (Electron Transfer) with chlorite to form chlorine dioxide. As chlorine dioxide accumulates in solution, chlorite consumption slows down and ClO 2 reaches a maximum as the system reaches equilibrium. In phosphate buffer at pH 6.90, manganese(IV) oxo accumulates and its reaction with ClO 2 gives ClO 3 -. However, at pH 5.00 acetate buffer proton coupled electron transfer (PCET) from chlorite to manganese(IV) oxo is fast and irreversible leading to chlorate formation only via the putative manganese(V) oxo species. These differences underscore how PCET rates affect reaction pathways and mechanism. The ClO 2 product can be collected from the aqueous reaction mixture via purging with an inert gas, allowing for the preparation of chlorine dioxide on-demand.

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Section: Resultscontrasting

confidence: 57%

“…Our group has reported on the dismutation of chlorite under physiological pH using water-soluble ferric porphyrins [13,14]. In these model systems, the reaction proceeds for the most part to disproportionation products, chloride and chlorate, in 1:2 stoichiometry.…”

Section: Mechanistic Study Of a Manganese Porphyrin Catalyst For On-dmentioning

confidence: 99%

Mechanistic study of a manganese porphyrin catalyst for on-demand production of chlorine dioxide in water

Hicks

Xiong

Bougher

et al. 2015

J. Porphyrins Phthalocyanines

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“…32 An exception has been found when a highly fluorinated iron porphyrin is used (Figure 3.9). [Fe III (TF 4 TMAP)] catalyzes chlorite decomposition into O 2 and Cl À in addition to the chlorate producing pathway.…”

Section: Oxygen Evolving Chlorite Dismutasementioning

confidence: 99%

Oxygen Atom Transfer

Abu‐Omar

2010

Physical Inorganic Chemistry

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“…1,2 It is likewise difficult to reproduce efficiently using synthetic porphyrins. 3–5 The enzyme from the perchlorate respiring organism Dechloromonas aromatica ( Da Cld) is fast, highly efficient [maximal k cat = (2.0 ± 0.6) × 10 5 s –1 , and k cat / K M = (3.2 ± 0.4) × 10 7 M –1 s –1 , at pH 5.2 and 4 °C], and highly specific, producing one molecule of O 2 from each ClO 2 – even in the presence of large amounts of potential peroxidase (one-electron-donating) substrates. 6 Because the majority of perchlorate is man-made, it has only recently become a significant environmental contaminant.…”

mentioning

confidence: 99%

Understanding How the Distal Environment Directs Reactivity in Chlorite Dismutase: Spectroscopy and Reactivity of Arg183 Mutants

et al. 2012

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The chlorite dismutase from Dechloromonas aromatica (DaCld) catalyzes the highly efficient decomposition of chlorite to O2 and chloride. Spectroscopic, equilibrium thermodynamic, and kinetic measurements have indicated that Cld has two pH sensitive moieties; one is the heme, and Arg183 in the distal heme pocket has been hypothesized to be the second. This active site residue has been examined by site-directed mutagenesis to understand the roles of positive charge and hydrogen bonding in O–O bond formation. Three Cld mutants, Arg183 to Lys (R183K), Arg183 to Gln (R183Q), and Arg183 to Ala (R183A), were investigated to determine their respective contributions to the decomposition of chlorite ion, the spin state and coordination states of their ferric and ferrous forms, their cyanide and imidazole binding affinities, and their reduction potentials. UV–visible and resonance Raman spectroscopies showed that DaCld(R183A) contains five-coordinate high-spin (5cHS) heme, the DaCld(R183Q) heme is a mixture of five-coordinate and six-coordinate high spin (5c/6cHS) heme, and DaCld(R183K) contains six-coordinate low-spin (6cLS) heme. In contrast to wild-type (WT) Cld, which exhibits pKa values of 6.5 and 8.7, all three ferric mutants exhibited pH-independent spectroscopic signatures and kinetic behaviors. Steady state kinetic parameters of the chlorite decomposition reaction catalyzed by the mutants suggest that in WT DaCld the pKa of 6.5 corresponds to a change in the availability of positive charge from the guanidinium group of Arg183 to the heme site. This could be due to either direct acid–base chemistry at the Arg183 side chain or a flexible Arg183 side chain that can access various orientations. Current evidence is most consistent with a conformational adjustment of Arg183. A properly oriented Arg183 is critical for the stabilization of anions in the distal pocket and for efficient catalysis.

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Bioinspired Dismutation of Chlorite to Dioxygen and Chloride Catalyzed by a Water‐Soluble Iron Porphyrin

Cited by 37 publications

References 23 publications

Mechanistic study of a manganese porphyrin catalyst for on-demand production of chlorine dioxide in water

Mechanistic study of a manganese porphyrin catalyst for on-demand production of chlorine dioxide in water

Oxygen Atom Transfer

Understanding How the Distal Environment Directs Reactivity in Chlorite Dismutase: Spectroscopy and Reactivity of Arg183 Mutants

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