Crystallographic and spectroscopic characterization and reactivities of a mononuclear non-haem iron(III)-superoxo complex

Hong, Seung-Woo; Sutherlin, Kyle D.; Park, Jiyoung; Kwon, Euna; Siegler, Maxime A.; Solomon, Edward I.; Nam, Wonwoo

doi:10.1038/ncomms6440

Cited by 126 publications

(135 citation statements)

References 42 publications

(54 reference statements)

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“…21 In the crystal structure of [(TAML)Fe III (O 2 )] 2− (Figure 1c), the O 2 -unit is bound to an iron ion in a side-on (η 2 ) fashion with the O−O bond length of ∼1.32 Å, which is similar to those of Fe(II)−superoxo species found in homoprotocatechuate 2,3-dioxygenase (1.34 Å) 26 and other metal−superoxo complexes (1.2−1.3 Å). 27 The superoxo character of the O 2 ligand was further supported by the infrared spectrum taken in CH 3 CN at −40°C, exhibiting an isotopically sensitive band at 1260 cm −1 , which shifts to 1183 cm −1 upon substitution of 16 O with 18 O.…”

Section: Accounts Of Chemical Researchmentioning

confidence: 97%

“…27 The superoxo character of the O 2 ligand was further supported by the infrared spectrum taken in CH 3 CN at −40°C, exhibiting an isotopically sensitive band at 1260 cm −1 , which shifts to 1183 cm −1 upon substitution of 16 O with 18 O. 21 In reactivity studies, the [(TAML)Fe III (O 2 )] 2− complex showed reactivities in both electrophilic and nucleophilic oxidation reactions. In the oxidation of para-substituted 2,6-di-tert-butylphenols (para-X-2,6-tert-Bu 2 -C 6 H 2 OH) (Scheme 2, reaction a), we have observed a good correlation between reaction rates and O−H bond dissociation energies (BDE) of para-X-2,6-tert-Bu 2 -C 6 H 2 OH, demonstrating that the superoxo ligand in [(TAML)Fe III (O 2 )] 2− possesses an electrophilic character enabling O−H bond activation reactions.…”

Section: Accounts Of Chemical Researchmentioning

confidence: 98%

“…It is worth noting here that the nucleophilic reactivity of a copper(II)−superoxo complex was reported recently. 28 Another 21 Compared with the [(TAML)Fe III (O 2 )] 2− complex, (BDPP)Fe III (O 2 ) was generated at a low temperature, probably, due to a lesser thermal stability. 25 Although no structural information, such as the binding mode of the superoxo ligand (e.g., side-on versus end-on), was reported, all the spectroscopic data, including resonance Raman (rRaman; for example, an isotopically sensitive band at 1125 cm −1 ), Mossbauer, and EPR spectroscopies, supported the binding of a superoxo ligand to an iron(III) ion.…”

Section: Accounts Of Chemical Researchmentioning

confidence: 99%

“…3,22 Although iron(III)−superoxo species in heme systems were well characterized including crystal structures in the 1970s, 23,24 there are only a couple of synthetic nonheme iron(III)−superoxo complexes reported very recently. Those are the structurally and spectroscopically characterized side-on (η 2 ) iron(III)−superoxo complex, [(TAML)Fe III (O 2 )] 2− (Figure 1c), 21 and the spectroscopically characterized iron(III)−superoxo complex, (BDPP)Fe III (O 2 ) (H 2 BDPP, 2,6-bis(((S)-2-(diphenylhydroxymethyl)-1-pyrrolidinyl)methyl)pyridine). 25 The …”

Section: ■ Introductionmentioning

confidence: 99%

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Synthetic Mononuclear Nonheme Iron–Oxygen Intermediates

2015

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Mononuclear nonheme iron-oxygen species, such as iron-superoxo, -peroxo, -hydroperoxo, and -oxo, are key intermediates involved in dioxygen activation and oxidation reactions catalyzed by nonheme iron enzymes. Because these iron-oxygen intermediates are short-lived due to their thermal instability and high reactivity, it is challenging to investigate their structural and spectroscopic properties and reactivity in the catalytic cycles of the enzymatic reactions themselves. One way to approach such problems is to synthesize biomimetic iron-oxygen complexes and to tune their geometric and electronic structures for structural characterization and reactivity studies. Indeed, a number of biologically important iron-oxygen species, such as mononuclear nonheme iron(III)-superoxo, iron(III)-peroxo, iron(III)-hydroperoxo, iron(IV)-oxo, and iron(V)-oxo complexes, were synthesized recently, and the first X-ray crystal structures of iron(III)-superoxo, iron(III)-peroxo, and iron(IV)-oxo complexes in nonheme iron models were successfully obtained. Thus, our understanding of iron-oxygen intermediates in biological reactions has been aided greatly from the studies of the structural and spectroscopic properties and the reactivities of the synthetic biomimetic analogues. In this Account, we describe our recent results on the synthesis and characterization of mononuclear nonheme iron-oxygen complexes bearing simple macrocyclic ligands, such as N-tetramethylated cyclam ligand (TMC) and tetraamido macrocyclic ligand (TAML). In the case of iron-superoxo complexes, an iron(III)-superoxo complex, [(TAML)Fe(III)(O2)](2-), is described, including its crystal structure and reactivities in electrophilic and nucleophilic oxidative reactions, and its properties are compared with those of a chromium(III)-superoxo complex, [(TMC)Cr(III)(O2)(Cl)](+), with respect to its reactivities in hydrogen atom transfer (HAT) and oxygen atom transfer (OAT) reactions. In the case of iron-peroxo intermediates, an X-ray crystal structure of an iron(III)-peroxo complex binding the peroxo ligand in a side-on (η(2)) fashion, [(TMC)Fe(III)(O2)](+), is described. In addition, iron(III)-peroxo complexes binding redox-inactive metal ions are described and discussed in light of the role of redox-inactive metal ions in O-O bond activation in cytochrome c oxidase and O2-evolution in photosystem II. In the case of iron-hydroperoxo intermediates, mononuclear nonheme iron(III)-hydroperoxo complexes can be generated upon protonation of iron(III)-peroxo complexes or by hydrogen atom abstraction (HAA) of hydrocarbon C-H bonds by iron(III)-superoxo complexes. Reactivities of the iron(III)-hydroperoxo complexes in both electrophilic and nucleophilic oxidative reactions are described along with a discussion of O-O bond cleavage mechanisms. In the last section of this Account, a brief summary is presented of developments in mononuclear nonheme iron(IV)-oxo complexes since the first structurally characterized iron(IV)-oxo complex, [(TMC)Fe(IV)(O)](2+), was reported. Although the f...

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Section: Accounts Of Chemical Researchmentioning

confidence: 97%

Section: Accounts Of Chemical Researchmentioning

confidence: 98%

Section: Accounts Of Chemical Researchmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Synthetic Mononuclear Nonheme Iron–Oxygen Intermediates

2015

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“…[45] On the other hand, the high-spin (S = 5/2) Fe III ─OOH intermediate, proposed to be formed in Rieske dioxygenases (RDO), [157,158,159] should have oxidant ability in electrophilic aromatic substitution reactions (note that alternative intermediates in RDO were also proposed [160,161] Figure 2) was crystallographically defined only as late as in 2014. [165] This synthetic system was shown to undergo both an aliphatic C─H activation and nucleophilic oxidation reaction. In any case, due to the limited body of experimental data, theoretical insight on reaction mechanisms that would involve the ferric-superoxo structure are therefore of particular importance.…”

Section: Mononuclear Ferric-hydroperoxo Active Site: C─h + Hoo─fe IIImentioning

confidence: 99%

Mono- and binuclear non-heme iron chemistry from a theoretical perspective

et al. 2016

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In this minireview, we provide an account of the current state-of-the-art developments in the area of mono-and binuclear non-heme enzymes (NHFe and NHFe2) and the smaller NHFe(2) synthetic models, mostly from a theoretical and computational perspective. The sheer complexity, and at the same time the beauty, of the NHFe(2) world represent a challenge for both experimental as well as theoretical methods. We emphasize that the concerted progress on both theoretical and experimental side is a conditio sine qua non for future understanding, exploration and utilization of the NHFe(2) systems.After briefly discussing the current challenges and advances in the computational methodology, we review the recent spectroscopic and computational studies of NHFe(2) enzymatic and inorganic systems and highlight the correlations between various experimental data (spectroscopic, kinetic, thermodynamic, electrochemical) and computations. Throughout, we attempt to keep in mind the most fascinating and attractive phenomenon in the NHFe(2) chemistry which is the fact that despite the strong oxidative power of many reactive intermediates, the NHFe(2) enzymes perform catalysis with high selectivity. We conclude with our personal viewpoint and hope that further developments in quantum chemistry and especially in the field of multireference wave function methods are needed to have a solid theoretical basis for the NHFe(2) studies, mostly by providing benchmarking and calibration of the computationally efficient and easy-to-use DFT methods.

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Characterization of Mononuclear Non‐heme Iron(III)‐Superoxo Complex with a Five‐Azole Ligand Set

et al. 2015

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Reaction of O 2 with ah igh-spin mononuclear iron(II) complex supported by af ive-azole donor set yields the corresponding mononuclear non-heme iron(III)-superoxo species,w hich was characterized by UV/Vis spectroscopya nd resonance Raman spectroscopy.1 HNMR analysis reveals diamagnetic nature of the superoxo complex arising from antiferromagnetic coupling between the spins on the low-spin iron(III) and superoxide. This superoxo species reacts with Hatom donating reagents to give al ow-spin iron(III)-hydroperoxo species showing characteristic UV/Vis,r esonance Raman, and EPR spectra.

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Crystallographic and spectroscopic characterization and reactivities of a mononuclear non-haem iron(III)-superoxo complex

Cited by 126 publications

References 42 publications

Synthetic Mononuclear Nonheme Iron–Oxygen Intermediates

Synthetic Mononuclear Nonheme Iron–Oxygen Intermediates

Mono- and binuclear non-heme iron chemistry from a theoretical perspective

Characterization of Mononuclear Non‐heme Iron(III)‐Superoxo Complex with a Five‐Azole Ligand Set

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