Direct evidence of heme-tert-butyl peroxide adduct formation demonstrated by simultaneous ESR and optical measurements

Tajima, Kunihiko; Jinno, Junichi; Ishizu, Kazuhiko; Sakurai, Hiromu; Ohya-Nishiguchi, Hiroaki

doi:10.1021/ic00303a020

Cited by 46 publications

(37 citation statements)

References 3 publications

(3 reference statements)

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“…These studies were able to show that the observed species were five-coordinate and high-spin on the basis of their electronic absorption, EPR, and 1 H NMR spectra [50][51][52]. Compounds 18a-19 ( Figure 8) were the first six-coordinate examples [53][54][55] and differed from their five-coordinate counterparts insofar as they displayed EPR spectra characterized by a low g dispersion, consistent with a low-spin Fe(III) center and similar to spectra reported for hydroperoxo (alkylperoxo) adducts of hemoglobin, horseradish peroxidase, and bleomycin [56][57][58].…”

Section: Fe(iii)-hydroperoxo (Alkylperoxo) Intermediatesmentioning

confidence: 92%

“…EPR studies have also demonstrated that changes in spin-state tend to accompany coordination of an additional axial ligand for these systems, with five-and six-coordinate species often being in high-and low-spin states, respectively [55]. These differences can have significant mechanistic implications for O-O bond cleavage.…”

Section: Fe(iii)-hydroperoxo (Alkylperoxo) Intermediatesmentioning

confidence: 99%

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Transition Metal Complexes and the Activation of Dioxygen

Yee

Tolman

2014

Metal Ions in Life Sciences

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In order to address how diverse metalloprotein active sites, in particular those containing iron and copper, guide O₂binding and activation processes to perform diverse functions, studies of synthetic models of the active sites have been performed. These studies have led to deep, fundamental chemical insights into how O₂coordinates to mono- and multinuclear Fe and Cu centers and is reduced to superoxo, peroxo, hydroperoxo, and, after O-O bond scission, oxo species relevant to proposed intermediates in catalysis. Recent advances in understanding the various factors that influence the course of O₂activation by Fe and Cu complexes are surveyed, with an emphasis on evaluating the structure, bonding, and reactivity of intermediates involved. The discussion is guided by an overarching mechanistic paradigm, with differences in detail due to the involvement of disparate metal ions, nuclearities, geometries, and supporting ligands providing a rich tapestry of reaction pathways by which O₂is activated at Fe and Cu sites.

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Section: Fe(iii)-hydroperoxo (Alkylperoxo) Intermediatesmentioning

confidence: 92%

Section: Fe(iii)-hydroperoxo (Alkylperoxo) Intermediatesmentioning

confidence: 99%

Transition Metal Complexes and the Activation of Dioxygen

Yee

Tolman

2014

Metal Ions in Life Sciences

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“…However, it has been a challenging task, mostly due to the highly destabilized nature of low-spin 6C heme Fe III –OOH intermediates when compared to their alkyl- or acyl-peroxo counterparts. 146,347,554–557…”

Section: Heme/dioxygen Interactions: From Biology To Model Systemsmentioning

confidence: 99%

Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function

et al. 2018

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Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H+/4e− reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements. This review encompasses important aspects of heme-O2 and copper–O2 (bio)chemistries as they relate to the design and interpretation of small molecule model systems and provides perspectives from fundamental coordination chemistry, which can be applied to the understanding of HCO activity. We focus on recent advancements from studies of heme–Cu models, evaluating experimental and computational results, which highlight important fundamental structure–function relationships. Finally, we provide an outlook for future potential contributions from synthetic inorganic chemistry and discuss their implications with relevance to biological O2-reduction.

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“…It was also noted [82] that model Fe III -porphyrinates axially coordinated by an alkyl peroxide and a variety of sixth ligands, including methoxide [94][95][96], imidazolate [97], or a second alkyl peroxide [98], exhibit EPR spectra with compressed heme anisotropy, P g 2 $ 14. In addition, the sum of the squared g values in the EPR spectra of the Fe III -OOH complexes of cytochrome P450 cam [66] and myoglobin [67] is also approximately 14, suggesting that the axial coordination of an alkylperoxide or hydroperoxide ligand in low-spin ferric porphyrinates would induce a (d xy ) 1 electron configuration.…”

Section: Increasing the Reactivity Of The Heme Macrocycle To Activelymentioning

confidence: 99%