Synthesis and characterization of a tris(2-hydroxyphenyl)methane-based cryptand and its triiron(iii) complex

Guillet, Gary L.; Sloane, Forrest T.; Dumont, Matthieu; Abboud, Khalil A.; Murray, Leslie J.

doi:10.1039/c2dt30312d

Cited by 22 publications

(9 citation statements)

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“…This conclusion was supported by EPR analysis of the oxygenated complexes, which showed the signal for a mononuclear Cu(II) center and the remaining two Cu(II) centers linked by hydroxo groups. − Magnetic studies revealed a ferromagnetically coupled Cu(II)Cu(II) center along with an isolated Cu(II) in these complexes . Although these tricopper complexes do not typically support hydrocarbon oxidation, they represent a popular approach to the problem, and ligand-assisted formation of trinuclear complexes has been reported for other metal ions such as manganese, iron, cobalt, and zinc, as well. − …”

Section: Toward the Development Of A Biomimetic Catalystmentioning

confidence: 86%

Alkane Oxidation: Methane Monooxygenases, Related Enzymes, and Their Biomimetics

et al. 2017

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Methane monooxygenases (MMOs) mediate the facile conversion of methane into methanol in methanotrophic bacteria with high efficiency under ambient conditions. Because the selective oxidation of methane is extremely challenging, there is considerable interest in understanding how these enzymes carry out this difficult chemistry. The impetus of these efforts is to learn from the microbes to develop a biomimetic catalyst to accomplish the same chemical transformation. Here, we review the progress made over the past two to three decades toward delineating the structures and functions of the catalytic sites in two MMOs: soluble methane monooxygenase (sMMO) and particulate methane monooxygenase (pMMO). sMMO is a water-soluble three-component protein complex consisting of a hydroxylase with a nonheme diiron catalytic site; pMMO is a membrane-bound metalloenzyme with a unique tricopper cluster as the site of hydroxylation. The metal cluster in each of these MMOs harnesses O to functionalize the C-H bond using different chemistry. We highlight some of the common basic principles that they share. Finally, the development of functional models of the catalytic sites of MMOs is described. These efforts have culminated in the first successful biomimetic catalyst capable of efficient methane oxidation without overoxidation at room temperature.

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Section: Toward the Development Of A Biomimetic Catalystmentioning

confidence: 86%

Alkane Oxidation: Methane Monooxygenases, Related Enzymes, and Their Biomimetics

et al. 2017

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“…Herein, we report that a family of triiron complexes housed within a tris(β-diketiminate) cyclophane effect the catalytic conversion of N 2 to N(SiMe 3 ) 3 using KC 8 and Me 3 SiCl. Notably, the series of complexes span varying oxidation states and ancillary bridging ligands (see Figure ) allowing for the first systematic evaluation of the effect of nitrogenase-relevant ancillary ligands on dinitrogen activation. − Our results demonstrate that the noncyclophane donors are labile under reducing conditions as a putative μ 3 -nitridotriiron(II) complex is observed as a major and common product of most reactions.…”

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confidence: 85%

Catalytic Silylation of Dinitrogen by a Family of Triiron Complexes

et al. 2018

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A series of triiron complexes supported by a tris(β-diketiminate)cyclophane (L3–) catalyze the reduction of dinitrogen to tris(trimethylsilyl)amine using KC8 and Me3SiCl. Employing Fe3Br3L affords 83 ± 7 equiv. NH4+/complex after protonolysis, which is a 50% yield based on reducing equivalents. The series of triiron compounds tested evidences the subtle effects of ancillary donors, including halides, hydrides, sulfides, and carbonyl ligands, and metal oxidation state on N(SiMe3)3 yield, and highlight Fe3(μ3-N)L as a common species in product mixtures. These results suggest that ancillary ligands can be abstracted with Lewis acids under reducing conditions.

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“…Similar observations have been made previously in the case of similar metallocryptand systems. 47,48 However, we cannot discount potential weak electrostatic couplings between each Mn center. Negligible differences in the electrochemical features were observed between complexes 1 and 1c, leading us to suggest that each Salen moiety within the cryptand structure 1 acts as a discrete entity and does not influence the redox potentials of the other Salen subunits.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Tri-Manganese(III) Salen-Based Cryptands: A Metal Cooperative Antioxidant Strategy that Overcomes Ischemic Stroke Damage In Vivo

et al. 2020

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Oxidative stress is one of the hallmarks of ischemic stroke. Catalase-based (CAT) biomimetic complexes are emerging as promising therapeutic candidates that are expected to act as neuroprotectants for ischemic stroke by decreasing the damaging effects from H2O2. Unfortunately, these molecules result in the unwanted production of the harmful hydroxyl radical, HO•. Here, we report a series of salen-based tri-manganese (Mn(III)) metallocryptands (1–3) that function as catalase biomimetics. These cage-like molecules contain a unique “active site” with three Mn centers in close proximity, an arrangement designed to facilitate metal cooperativity for the effective dismutation of H2O2 with minimal HO• production. In fact, significantly greater oxygen production is seen for 1–3 as compared to the monomeric Mn(Salen) complex, 1c. The most promising system, 1, was studied in further detail and found to confer a greater therapeutic benefit both in vitro and in vivo than the monomeric control system, 1c, as evident from inter alia studies involving a rat model of ischemic stroke damage and supporting histological analyses. We thus believe that metallocryptand 1 and its analogues represent a new and seemingly promising strategy for treating oxidative stress related disorders.

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Synthesis and characterization of a tris(2-hydroxyphenyl)methane-based cryptand and its triiron(iii) complex

Cited by 22 publications

References 50 publications

Alkane Oxidation: Methane Monooxygenases, Related Enzymes, and Their Biomimetics

Alkane Oxidation: Methane Monooxygenases, Related Enzymes, and Their Biomimetics

Catalytic Silylation of Dinitrogen by a Family of Triiron Complexes

Tri-Manganese(III) Salen-Based Cryptands: A Metal Cooperative Antioxidant Strategy that Overcomes Ischemic Stroke Damage In Vivo

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