Redox Reactivity of a Mononuclear Manganese-Oxo Complex Binding Calcium Ion and Other Redox-Inactive Metal Ions

Sankaralingam, Muniyandi; Lee, Yong Min; Pineda‐Galvan, Yuliana; Karmalkar, Deepika G.; Seo, Mi Sook; Jeon, S. H.; Pushkar, Yulia; Fukuzumi, Shunichi; Nam, Wonwoo

doi:10.1021/jacs.8b11492

Cited by 80 publications

(110 citation statements)

References 126 publications

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“…Finally, the determination that the weak interaction in (OEP)Co(NO⋅BF 3 ) was sufficient to enable reaction with external NO is consistent with our observation that both (OEP)Co(NO) and (OEP)Fe(NO) in THF at 0 °C are also activated by the weak Lewis acid [K(2.2.2)]OTf (2.5 equiv) towards N–N coupling with excess NO to generate N 2 O in detectable but trace (approximately 2–4 %) yields (Supporting Information, Figures S9–10). Our observed non‐redox active Lewis‐acid‐promoted NO coupling reactions involving (OEP)Co(NO) and (OEP)Fe(NO) add to the range of non‐redox‐active Lewis‐acid‐promoted reactions including those of metal‐oxo complexes …”

Section: Resultsmentioning

confidence: 83%

Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N₂O

et al. 2019

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Some bacterial heme proteins catalyze the coupling of two NO molecules to generate N2O. We previously reported that a heme Fe–NO model engages in this N−N bond‐forming reaction with NO. We now demonstrate that (OEP)CoII(NO) similarly reacts with 1 equiv of NO in the presence of the Lewis acids BX3 (X=F, C6F5) to generate N2O. DFT calculations support retention of the CoII oxidation state for the experimentally observed adduct (OEP)CoII(NO⋅BF3), the presumed hyponitrite intermediate (P.+)CoII(ONNO⋅BF3), and the porphyrin π‐radical cation by‐product of this reaction, and that the π‐radical cation formation likely occurs at the hyponitrite stage. In contrast, the Fe analogue undergoes a ferrous‐to‐ferric oxidation state conversion during this reaction. Our work shows that cobalt hemes are chemically competent to engage in the NO‐to‐N2O conversion reaction.

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Section: Resultsmentioning

confidence: 83%

Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N₂O

et al. 2019

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“…Our observed non-redox active Lewis-acid-promoted NO coupling reactions involving (OEP)Co(NO) and (OEP)Fe(NO) add to the range of non-redox-active Lewis-acid-promoted reactions including those of metal-oxo complexes. [37][38][39]…”

Section: Resultsmentioning

confidence: 99%

Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N₂O

et al. 2019

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Some bacterial heme proteins catalyze the coupling of two NO molecules to generate N 2 O. We previously reported that aheme Fe-NO model engages in this N À Nbond-forming reaction with NO.W en ow demonstrate that (OEP)Co II (NO) similarly reacts with 1equiv of NO in the presence of the Lewis acids BX 3 (X = F, C 6 F 5 )t og enerate N 2 O. DFT calculations support retention of the Co II oxidation state for the experimentally observed adduct (OEP)Co II (NO·BF 3 ), the presumed hyponitrite intermediate (PC + )Co II (ONNO·BF 3 ), and the porphyrin p-radical cation by-product of this reaction, and that the p-radical cation formation likely occurs at the hyponitrite stage.Incontrast, the Fe analogue undergoes aferrous-to-ferric oxidation state conversion during this reaction. Our work shows that cobalt hemes are chemically competent to engage in the NO-to-N 2 Oc onversion reaction.

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“…High‐valent metal‐oxo species including Mn IV ‐oxo complexes have been invoked as key intermediates, which are capable of oxidation of water in the oxygen evolving complex in photosystem II as well as a variety of substrates . Redox‐inactive metal ions such as Ca 2+ and Sc 3+ are reported to bind with the oxo moiety of Mn IV ‐oxo complexes, resulting that the one‐electron reduction potential ( E red ) of Mn IV ‐oxo intermediates shifted tremendously in the positive direction . Thus, binding of redox‐inactive metal ions to Mn IV ‐oxo intermediates converts them to much stronger oxidants .…”

Section: Metal Complexes As Photocatalystsmentioning

confidence: 99%

“…Redox‐inactive metal ions such as Ca 2+ and Sc 3+ are reported to bind with the oxo moiety of Mn IV ‐oxo complexes, resulting that the one‐electron reduction potential ( E red ) of Mn IV ‐oxo intermediates shifted tremendously in the positive direction . Thus, binding of redox‐inactive metal ions to Mn IV ‐oxo intermediates converts them to much stronger oxidants . The ET reactivity of metal‐oxo intermediates in the photoexcited states are expected to be much enhanced, when such excited metal‐oxo species become superoxidants.…”

Section: Metal Complexes As Photocatalystsmentioning

confidence: 99%

Photoinduced Generation of Superoxidants for the Oxidation of Substrates with High C−H Bond Dissociation Energies

et al. 2019

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Oxidation of substrates, such as methane, with large C−H bond dissociation energies usually requires harsh reaction conditions, such as high temperature and pressure. The use of photoexcited states of oxidants enables the oxidation of substrates which would otherwise be unable to react thermally. This Review focuses on photoinduced generation of strong inorganic and organic oxidants, which enables the oxidation of substrates with strong C−H bonds. For example, photoexcitation of a CeIV‐alkoxide complex results in the cleavage of Ce−O bond to produce an alkoxyl radical, which can abstract a hydrogen atom from methane to afford a methyl radical, leading to amination of methane with tert‐butyloxycarbonyl (Boc)‐protected monomethylhydrazine. Hydrogen atom abstraction from alkanes also occurs induced by the photoexcited state of tetrabutylammonium decatungstate, leading to alkylations and acylation of both aromatic and aliphatic N‐tosylimines. Photoexcitation of Bi‐ and V‐containing beta zeolites also results in hydrogen atom abstraction from methane to produce methanol at ambient temperature. The photoexcited state of a manganese(IV)‐oxo complex binding with two Sc3+ ions has a surprisingly long lifetime (6.4 μs), and is able to oxidize benzene to produce phenol. Chlorine radicals, that can be generated by photoinduced oxidation of chloride ion by the photoexcited states of oxidants or by photoexcitation of a chlorine dioxide radical, abstracts a hydrogen atom from alkanes including methane to produce alkyl radicals, which can be converted to the oxygenated products. Photoinduced oxidation of methane was also made possible by mixing photosystem II (PSII) and the membrane fraction of a particular form of methane monooxygenase. A PSII model reaction has been achieved by using p‐benzoquinone derivatives as plastoquinone analogues with a non‐heme FeII catalyst in the presence of H2O under photoirradiation, to yield dioxygen with the corresponding hydroquinone derivatives.

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Redox Reactivity of a Mononuclear Manganese-Oxo Complex Binding Calcium Ion and Other Redox-Inactive Metal Ions

Cited by 80 publications

References 126 publications

Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N₂O

Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N₂O

Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N₂O

Photoinduced Generation of Superoxidants for the Oxidation of Substrates with High C−H Bond Dissociation Energies

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Redox Reactivity of a Mononuclear Manganese-Oxo Complex Binding Calcium Ion and Other Redox-Inactive Metal Ions

Cited by 80 publications

References 126 publications

Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N2O

Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N2O

Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N2O

Photoinduced Generation of Superoxidants for the Oxidation of Substrates with High C−H Bond Dissociation Energies

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Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N₂O

Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N₂O

Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N₂O