Ligand Taxonomy for Bioinorganic Modeling of Dioxygen‐Activating Non‐Heme Iron Enzymes

Park, Hyunchang; Lee, Dongwhan

doi:10.1002/chem.201904975

Cited by 20 publications

(13 citation statements)

References 171 publications

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“…The 2H1C has been an inspiration for the design of many biomimetic ligands, [13] some of the most well‐known being the Tp , [14] TPA , [15] 14‐TMC , [16] PyTACN , [17] PyNMe 3 , [18] BPBP , [19] and N4Py [20] ligands (Figure 2, top). These polydentate N‐donor ligands support the formation of high‐valent iron‐oxo species and have greatly helped the scientific community understand the role of such entities in enzymatic reactions and oxidation catalysis [21, 22] .…”

Section: Introductionmentioning

confidence: 99%

Structurally Modelling the 2‐His‐1‐Carboxylate Facial Triad with a Bulky N,N,O Phenolate Ligand

Monkcom

Bruin

Vries

et al. 2021

Chemistry A European J

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We present the synthesis and coordination chemistry of a bulky, tripodal N,N,O ligand, ImPh2NNOtBu (L), designed to model the 2‐His‐1‐carboxylate facial triad (2H1C) by means of two imidazole groups and an anionic 2,4‐di‐tert‐butyl‐subtituted phenolate. Reacting K‐L with MCl2 (M = Fe, Zn) affords the isostructural, tetrahedral non‐heme complexes [Fe(L)(Cl)] (1) and [Zn(L)(Cl)] (2) in high yield. The tridentate N,N,O ligand coordination observed in their X‐ray crystal structures remains intact and well‐defined in MeCN and CH2Cl2 solution. Reacting 2 with NaSPh affords a tetrahedral zinc thiolate complex, [Zn(L)(SPh)] (4), that is relevant to isopenicillin N synthase (IPNS) biomimicry. Cyclic voltammetry studies demonstrate the ligand's redox non‐innocence, where phenolate oxidation is the first electrochemical response observed in K‐L, 2 and 4. However, the first electrochemical oxidation in 1 is iron‐centred, the assignment of which is supported by DFT calculations. Overall, ImPh2NNOtBu provides access to well‐defined mononuclear, monoligated, N,N,O‐bound metal complexes, enabling more accurate structural modelling of the 2H1C to be achieved.

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Section: Introductionmentioning

confidence: 99%

Structurally Modelling the 2‐His‐1‐Carboxylate Facial Triad with a Bulky N,N,O Phenolate Ligand

Monkcom

Bruin

Vries

et al. 2021

Chemistry A European J

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“…Soon after the report that Fe(tpa) complexes could reproduce the chemistry of non-heme Fe oxygenases with H 2 O 2 , ,, several attempts to modify this catalytic system were carried out (Figure ). − However, heterolytic H 2 O 2 activation at Fe (and Mn) centers turned out to be rather sensitive, and what may look like a minor modification of the catalytic system can greatly affect its reactivity, often leading to uncontrolled free radical oxidations . In this regard, catalyst stability is paramount: its degradation either releases the metal ion, which promotes a Fenton-type reactivity, or forms inactive μ-oxo and μ-carboxylate dimers.…”

Section: Principles Of Rational Catalyst Designmentioning

confidence: 99%

Rational Design of Bioinspired Catalysts for Selective Oxidations

2020

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Recognizing Nature’s unique ability to perform challenging oxygenation reactions with exquisite selectivity parameters at iron-dependent oxygenases, chemists have long sought to understand and mimic these enzymatic processes with artificial systems. In the last two decades, replication of the reactivity of non-heme iron oxygenases has become feasible even with simple coordination complexes of iron and manganese. A bona fide minimalistic functional model was the tetradentate-N4 ligand based iron complex [Fe(tpa)(CH3CN)2]2+(Fe(tpa), tpa = tris(2-methylpyridyl)amine), which activates H2O2 via a mechanism that mirrors key steps of enzymatic O2 activation processes at mononuclear iron centers: controlled O–O bond cleavage, generation of a high-valent FeO oxidant, and promotion of almost the full spectrum of its oxidative reactivity (C–H hydroxylation, olefin epoxidation, syn-dihydroxylation, and desaturation). These landmark discoveries set the mechanistic framework to use iron coordination complexes with nitrogen-rich ligands as catalysts for oxidizing organic substrates under synthetically relevant conditions. Due to proof-of-concept demonstrations of the potential of these catalysts in organic synthesis, this chemistry has flourished over the past decade. In parallel to the realization of the potential of this class of catalysts in diverse organic transformations, effort has been spent to manipulate the catalyst structure with the aim of tuning both the reactivity and selectivity of the oxidation reactions. This perspective provides an overview of the progress of this research. Some key features of the archetypical Fe(tpa) catalyst have stayed surprisingly true throughout this evolution, but a series of alterations that modulate its electronic, steric, or binding properties allowed a rational elicitation of a specific reactivity or selectivity. In some cases, the replacement of iron by manganese has also proven beneficial. Overall, the rational optimization of the catalyst structure has enabled the development of highly asymmetric olefin epoxidation, syn-dihydroxylation, and site-selective and even enantioselective C–H oxidation reactions.

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“…These structural motifs have been extensively modeled using pyridyl based ligands (Figure 1) that have been shown to support high valent metal-oxo species capable of activating C-H bonds of substrates similarly to their enzymatic counterparts [18][19][20][21][22][23]. The appeal of these heterocyclic N-donor groups is that they function as strong σ donors to support high oxidation states and provide flexibility in their functional derivatization for the tuning of primary coordination spheres [24]. to support high oxidation states and provide flexibility in their functional derivatization for the tuning of primary coordination spheres [24].…”

Section: Introductionmentioning

confidence: 99%

“…The appeal of these heterocyclic N-donor groups is that they function as strong σ donors to support high oxidation states and provide flexibility in their functional derivatization for the tuning of primary coordination spheres [24]. to support high oxidation states and provide flexibility in their functional derivatization for the tuning of primary coordination spheres [24]. It is of interest to link these biomimetic ligand scaffolds to solid supports towards the development of heterogeneous catalysts.…”

Section: Introductionmentioning

confidence: 99%

Facile Synthesis and Characterization of a Bromine-Substituted (Chloromethyl)Pyridine Precursor towards the Immobilization of Biomimetic Metal Ion Chelates on Functionalized Carbons

Handlovic

Moreira

Khan

et al. 2021

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Multidentate ligands involving tethered pyridyl groups coordinated to transition metal ions have been frequently used to mimic the 3-histidine (3H), 2-histidine-1-carboxylate (2H1C) brace motifs or other combinations of histidine and carboxylate endogenous ligating residues found in bioinorganic metalloenzymes. It is of interest to immobilize these ligand chelates onto heterogeneous supports. This, however, requires the use of bromine-substituted (chloromethyl)pyridines, whose current synthetic routes involve the use of extremely pyrophoric chemicals, such as n-butyllithium that require cryogenic reaction conditions, and toxic chemicals, such as thionyl chloride, that are challenging to handle and require extensive hazard controls. Herein, we report alternative methodologies towards the syntheses of 2-bromo-6-hydroxymethylpyridine and 2-bromo-6-chloromethylpyridine from inexpensive commercially available 2,6-dibromopyridine using isopropylmagnesium chloride lithium chloride complex (Turbo Grignard) and cyanuric chloride which are easier to handle and require milder reaction conditions than the conventional reagents. Gas chromatography-mass spectrometry (GC-MS) methods were developed and simple 1H- and 13C- nuclear magnetic resonance (NMR) and Fourier-transform infrared (FT-IR) spectroscopies were also used to monitor the conversion of both reaction steps and showed that products could be obtained and isolated through simple workups without the presence of unreacted starting material or undesired overchlorinated 2-chloro-6-chloromethylpyridine side product.

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Ligand Taxonomy for Bioinorganic Modeling of Dioxygen‐Activating Non‐Heme Iron Enzymes

Cited by 20 publications

References 171 publications

Structurally Modelling the 2‐His‐1‐Carboxylate Facial Triad with a Bulky N,N,O Phenolate Ligand

Structurally Modelling the 2‐His‐1‐Carboxylate Facial Triad with a Bulky N,N,O Phenolate Ligand

Rational Design of Bioinspired Catalysts for Selective Oxidations

Facile Synthesis and Characterization of a Bromine-Substituted (Chloromethyl)Pyridine Precursor towards the Immobilization of Biomimetic Metal Ion Chelates on Functionalized Carbons

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