Observation of a CuII2(μ‐1,2‐peroxo)/CuIII2(μ‐oxo)2 Equilibrium and its Implications for Copper–Dioxygen Reactivity

Kieber‐Emmons, Matthew T.; Ginsbach, Jake W.; Wick, Patrick K.; Lucas, Heather R.; Helton, Matthew E.; Lucchese, Baldo; Suzuki, Masatatsu; Zuberbühler, Andreas D.; Karlin, Kenneth D.; Solomon, Edward I.

doi:10.1002/anie.201402166

Cited by 56 publications

(54 citation statements)

References 29 publications

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“…6d,14 Under identical reaction conditions, oxygenation of the Cu I ( DMA N 3 O), possessing three N-donors and an ether O-atom, leads to the initial formation of a ( μ -1,2-peroxo)Cu II 2 which rapidly (~ 1 min) converts to a bis( μ -oxo)Cu III 2 species with very similar UV-vis spectrum as for the case with DMA N 3 . 6d,15 Thus, as seen before, 6d,16 the oxygen atom of the ether arm in DMA N 3 O has an extremely weak to non-existent interaction with the copper ion in the oxygenated product. We find that for Cu I ( DMA N 4 ) in MeTHF (Scheme 2c), both Cu II –superoxo and ( μ -1,2-peroxo)Cu II 2 complexes are generated 7 as in the case of DMA N 3 S. This strongly suggests that the S (thioether) -atom donor of DMA N 3 S ligand is coordinated in both Cu II –superoxo/ μ -1,2-peroxo complexes, 2 S and 2 P .…”

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confidence: 58%

A N₃S_(thioether)-Ligated Cu^II-Superoxo with Enhanced Reactivity

et al. 2015

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Previous efforts to synthesize a cupric superoxide complex possessing a thioether donor have resulted in the formation of an end-on trans-peroxodicopper(II) species, [{(Ligand)CuII}2(μ-1,2-O22−)]2+. Redesign/modification of previous N3S tetradentate ligands has now allowed for the stabilization of the monomeric, superoxide product possessing a S(thioether)-ligation, [(DMAN3S)CuII(O2•−)]+ (2S), as characterized by UV-vis and resonance Raman (rR) spectroscopies. This complex mimics the putative CuII(O2•−) active species of the copper monooxygenase PHM and exhibits enhanced reactivity towards both O-H and C-H substrates in comparison to close analogues [(L)CuII(O2•−)]+, where L contains only nitrogen donor atoms. Cu-S(thioether) ligation with its weaker donor ability (relative to an N-donor) are demonstrated by comparisons to the chemistry of analogue compounds.

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A N₃S_(thioether)-Ligated Cu^II-Superoxo with Enhanced Reactivity

et al. 2015

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“…Recent studies on O and T species with varied amine and imidazole ligation correlate more donating ligation to a systematic blue-shifting of the LMCT optical bands for complexes of the same structural type [21,22]. As many of these complexes are thermally sensitive and can exist as an equilibrium of isomers in solution ( vide infra ), resonance Raman (rR) is generally preferred over infrared spectroscopic characterization, as the former enables optical and vibrational correlations [26–28]. A superoxide stretching frequency (960–1130 cm −1 ) [4] is distinguished readily from that of a peroxide (720–960 cm −1 ) [2,24,13] or that of the bis-oxide core (590–620 cm −1 ) [29,30].…”

Section: Spectroscopic Characterizationmentioning

confidence: 99%

High-valent copper in biomimetic and biological oxidations

2016

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A long-standing debate in the Cu-O2 field has revolved around the relevance of the Cu(III) oxidation state in biological redox processes. The proposal of Cu(III) in biology is generally challenged as no spectroscopic or structural evidence exists currently for its presence. The reaction of synthetic Cu(I) complexes with O2 at low temperature in aprotic solvents provides the opportunity to investigate and define the chemical landscape of Cu-O2 species at a small molecule level of detail; eight different types are characterized structurally, three of which contain at least one Cu(III) center. Simple imidazole or histamine ligands are competent in these oxygenation reactions to form Cu(III) complexes. The combination of synthetic structural and reactivity data suggests (i) that Cu(I) should be considered as either a one or two electron reductant reacting with O2, (ii) that Cu(III) reduction potentials of these formed complexes are modest and well within the limits of a protein matrix and (iii) that primary amine and imidazole ligands are surprisingly good at stabilizing Cu(III) centers. These Cu(III) complexes are efficient oxidants for hydroxylating phenolate substrates with reaction hallmarks similar to that performed in biological systems. The remarkable ligation similarity of the synthetic and biological systems makes it difficult to continue to exclude Cu(III) from biological discussions.

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“…The main barrier to this determination has been the low solubility of the dendrimer complexes at the low temperatures necessary to record the spectra of the reaction intermediates. [33] Proposed Mechanism…”

Section: Kinetic Experiments With Catechol As Reducing Agentmentioning

confidence: 99%

Cooperative Effects in Copper Polyamidoamine Dendrimer Complexes Catalyzing the Reduction of Molecular Oxygen

et al. 2015

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Generation-dependent cooperation was observed in the reduction of molecular oxygen by a series of Cu 2+ complexes of pyridine-modified polyamidoamine (PAMAM) dendrimers. The cooperative behavior of the metal ions was examined by preparing (G2-G6)-dendri-PAMAM-(Py) n and testing the dendrimers for their ability to reduce oxygen catalytically in the presence of several Cu 2+ ion concentrations. Spectrophotometric measurements during the reactive metallic ion titrations revealed that the maximum numbers of reactive Cu 2+ ions available for O 2 reduction were 4.8, 7.6, 22.2, 57.3, and 81.7 in each of the second-to sixth-generation (G2-G6) dendrimer complexes, respectively. An analysis revealed

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Observation of a Cu^II₂(μ‐1,2‐peroxo)/Cu^III₂(μ‐oxo)₂ Equilibrium and its Implications for Copper–Dioxygen Reactivity

Cited by 56 publications

References 29 publications

A N₃S_(thioether)-Ligated Cu^II-Superoxo with Enhanced Reactivity

A N₃S_(thioether)-Ligated Cu^II-Superoxo with Enhanced Reactivity

High-valent copper in biomimetic and biological oxidations

Cooperative Effects in Copper Polyamidoamine Dendrimer Complexes Catalyzing the Reduction of Molecular Oxygen

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Observation of a CuII2(μ‐1,2‐peroxo)/CuIII2(μ‐oxo)2 Equilibrium and its Implications for Copper–Dioxygen Reactivity

Cited by 56 publications

References 29 publications

A N3S(thioether)-Ligated CuII-Superoxo with Enhanced Reactivity

A N3S(thioether)-Ligated CuII-Superoxo with Enhanced Reactivity

High-valent copper in biomimetic and biological oxidations

Cooperative Effects in Copper Polyamido­amine Dendrimer Complexes Catalyzing the Reduction of Molecular Oxygen

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Product

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Observation of a Cu^II₂(μ‐1,2‐peroxo)/Cu^III₂(μ‐oxo)₂ Equilibrium and its Implications for Copper–Dioxygen Reactivity

A N₃S_(thioether)-Ligated Cu^II-Superoxo with Enhanced Reactivity

A N₃S_(thioether)-Ligated Cu^II-Superoxo with Enhanced Reactivity

Cooperative Effects in Copper Polyamidoamine Dendrimer Complexes Catalyzing the Reduction of Molecular Oxygen