Oxygen Activation at Mononuclear Nonheme Iron Centers: A Superoxo Perspective

Mukherjee, Anusree; Cranswick, Matthew A.; Chakrabarti, Mrinmoy; Paine, Tapan Kanti; Fujisawa, Kiyoshi; Münck, Eckard; Que, Lawrence

doi:10.1021/ic901891n

Cited by 119 publications

(61 citation statements)

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“…In a more recent study, a variety of observations were interpreted to indicate the intermediacy of an iron(II)-superoxo species from the oxygenation of an iron(II)-benzoylformate complex 51 ( Figure 27) that models α-KG-dependent monooxygenase active sites [163]. A similar intermediate was proposed in studies of an Fe(II)-acetylacetone model of β-diketone dioxygenase [190].…”

Section: Monoiron Superoxo and Hydroperoxo Complexesmentioning

confidence: 80%

“…Indirect evidence for the intermediacy of an iron(II)-superoxo complex was also cited in studies of 52 ( Figure 27), which reacted with O 2 only in the presence of reductant and proton donors [191] or substrates with weak C-H bonds [192] to yield iron(III)-hydroperoxo or iron(IV)-oxo species. Mechanistic studies were interpreted to support a pathway Figure 27 Proposed non-heme iron(II)-superoxo complexes (adapted from [163] and [192]). …”

Section: Monoiron Superoxo and Hydroperoxo Complexesmentioning

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: Monoiron Superoxo and Hydroperoxo Complexesmentioning

confidence: 80%

Section: Monoiron Superoxo and Hydroperoxo Complexesmentioning

confidence: 99%

Transition Metal Complexes and the Activation of Dioxygen

Yee

Tolman

2014

Metal Ions in Life Sciences

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“…Here, the first intermediate (Int-1) observed after adding O 2 to the H200N-4NC complex is trapped and characterized using EPR and Möss-bauer (MB) spectroscopies. Int-1 is a high-spin ( (1)(2)(3)(4)(5)(6)(7)(8). Internal electron transfer to form an Fe III -superoxo species converts the kinetically inert triplet ground state of O 2 to a doublet that can participate in the many types of chemistry characteristic of this mechanistically diverse group of enzymes.…”

mentioning

confidence: 99%

Trapping and spectroscopic characterization of an Fe^III-superoxo intermediate from a nonheme mononuclear iron-containing enzyme

Mbughuni

Chakrabarti

Hayden

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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145

297

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Fe III -O 2 •− intermediates are well known in heme enzymes, but none have been characterized in the nonheme mononuclear Fe II enzyme family. Many steps in the O 2 activation and reaction cycle of Fe II -containing homoprotocatechuate 2,3-dioxygenase are made detectable by using the alternative substrate 4-nitrocatechol (4NC) and mutation of the active site His200 to Asn (H200N). Here, the first intermediate (Int-1) observed after adding O 2 to the H200N-4NC complex is trapped and characterized using EPR and Möss-bauer (MB) spectroscopies. Int-1 is a high-spin ( (1)(2)(3)(4)(5)(6)(7)(8). Internal electron transfer to form an Fe III -superoxo species converts the kinetically inert triplet ground state of O 2 to a doublet that can participate in the many types of chemistry characteristic of this mechanistically diverse group of enzymes. The same strategy is usually employed by heme-containing oxygenases and oxidases, leading in some cases to comparatively stable Fe III -superoxo intermediates that have been structurally and spectroscopically characterized (9-12). Instability of the putative superoxo intermediate in all mononuclear nonheme iron-containing enzymes has prevented similar characterization, although a superoxide level species has been reported for the dinuclear iron site of myo-inositol oxygenase (13).In recent studies of the nonheme Fe II -containing homoprotocatechuate 2,3-dioxygenase (2,3-HPCD), we have shown that three intermediates of the catalytic cycle can be trapped in one crystal for structural analysis (14). One of these intermediates has been proposed to be an Fe II -superoxo species based on the long Fe-O bond distances and an unexpected lack of planarity of the aromatic ring of the alternative substrate 4-nitrocatechol (4NC), which chelates the iron in ligand sites adjacent to that of the O 2 . In accord with the mechanism postulated for this enzyme class as illustrated in Scheme 1 (1, 8, 15-21), we have proposed that net electron transfer from 4NC through the Fe II to O 2 forms adjacent substrate and oxygen radicals (Scheme 1B). Recombination of the radicals would begin the ring cleavage and oxygen insertion reactions of this enzyme that eventually yield a muconic semialdehyde adduct as the product. A localized radical on the 4NC semiquinone at the incipient position of oxygen attack would account for the lack of ring planarity. Although this is the only structurally characterized nonheme Fe-superoxo species, the iron oxidation state differs from all of the other postulated Fe-superoxo intermediates.The mechanism that emerges from the structural and kinetic studies does not require a change in metal oxidation state to form a reactive intermediate (22). However, our studies of 2,3-HPCD in which Fe II is replaced with Mn II suggest that transient formaScheme 1. Proposed mechanism for extradiol dioxygenases. In the case of 2,3-HPCD, R is −CH 2 COO − and B is His200. When R is −NO 2 and His200 is changed to Asn, the reaction stalls before reaching intermediate C. Peroxide is slowly released a...

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“…Schiff's bases are able to stabilize various metal ions in different oxidation states and thereby control the performance of metals in a large variety of useful catalytic transformations. A variety of enzymes are able to catalyze different reactions such as oxidation, reduction and isomerization containing iron bound to porphyrin [1,2]. Several non-heme iron (III) complexes with mixed nitrogen sulfur coordination sphere have been reported [3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Structural Evaluation and Antibacterial Sensitivity of Iron (III) Complexes of 4-<i>n</i>-hexyloxybenzoylhydrazine with Some Aliphatic and Aromatic

et al. 2012

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The condensation reaction of N-alkylidene or N-arylidene-(4-n-hexyloxy)benzoylhydrazone [L] (1-7) where, R= formaldehyde (1), acetaldehyde (2), butyraldehyde (3), cinnamaldehyde (4), 4-N,N-dimethylaminobenzaldehyde (5), 2-hydroxybenzaldehyde (6) and 4-methoxybenzaldehyde (7) (11-14) were obtained by the direct reaction of the Schiff's bases with Fe 3+ ion. The complexes were characterized by magnetic moment measurement, UV-visible, infrared, 1 H-NMR and TGA (Thermo gravimetric analysis) studies. The Schiff's bases containing small alkyl group at the hydrazine moiety formed octahedral complexes, while the bulky/aryl/substituted aryl moiety, yielded five coordinated square-pyramidal complexes. The complexes were found to be quite stable and decomposition of the complexes ended with ferric oxide as final product. Complexes (10) and (13) showed no activity against all the bacteria. Complexes (8), (9) and (12) showed resistance while the complex (14) manifested intermediate antibacterial activity.

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Oxygen Activation at Mononuclear Nonheme Iron Centers: A Superoxo Perspective

Cited by 119 publications

References 66 publications

Transition Metal Complexes and the Activation of Dioxygen

Transition Metal Complexes and the Activation of Dioxygen

Trapping and spectroscopic characterization of an Fe^III-superoxo intermediate from a nonheme mononuclear iron-containing enzyme

Structural Evaluation and Antibacterial Sensitivity of Iron (III) Complexes of 4-<i>n</i>-hexyloxybenzoylhydrazine with Some Aliphatic and Aromatic

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Oxygen Activation at Mononuclear Nonheme Iron Centers: A Superoxo Perspective

Cited by 119 publications

References 66 publications

Transition Metal Complexes and the Activation of Dioxygen

Transition Metal Complexes and the Activation of Dioxygen

Trapping and spectroscopic characterization of an FeIII-superoxo intermediate from a nonheme mononuclear iron-containing enzyme

Structural Evaluation and Antibacterial Sensitivity of Iron (III) Complexes of 4-<i>n</i>-hexyloxybenzoylhydrazine with Some Aliphatic and Aromatic

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Trapping and spectroscopic characterization of an Fe^III-superoxo intermediate from a nonheme mononuclear iron-containing enzyme