A Highly Reactive and Catalytically Active Model System for Intradiol‐Cleaving Catechol Dioxygenases: Structure and Reactivity of Iron(<scp>III</scp>) Catecholate Complexes of <i>N,N</i>′‐Dimethyl‐2,11‐diaza[3.3](2,6)pyridinophane

Koch, W.; Krüger, Hans‐Jörg

doi:10.1002/anie.199526711

Cited by 106 publications

(58 citation statements)

References 12 publications

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“…The formation of intradiol cleavage products for the catecholate adduct of the iron(II) complex is expected of the six‐coordinate geometry, which favours a substrate‐activation rather than dioxygen‐activation pathway as the latter requires a vacant coordination site on the catecholate adduct for oxygen coordination followed by activation. The observation of smaller amounts of extradiol products for this iron(II) complex may be explained by invoking the partial displacement of the phen ligand from the coordination sphere containing more Lewis basic ligand donors (ethanol), which facilitates dioxygen attack on iron(III) for extradiol cleavage to occur.…”

Section: Resultsmentioning

confidence: 99%

Catalytic promiscuity of an iron(II)–phenanthroline complex

De¹,

Garai²,

Yadav

et al. 2016

Applied Organom Chemis

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A mononuclear iron(II) complex, [Fe(phen) 3 ]Cl 2 (1) (phen =1,10-phenanthroline), has been synthesized in crystalline phase and characterized using various spectroscopic techniques including single crystal X-ray diffraction. Crystal structure analysis revealed that 1 crystallizes in a monoclinic system with C2/m space group. Complex 1 acts as a functional model for a biomimetic catalyst promoting the aerobic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) through radical pathways with a significant turnover number (k cat =3.55 × 10 3 h À1 ) and exhibits catechol dioxygenase activity towards the same 3,5-DTBC substrate at room temperature in oxygen-saturated ethanol medium. The existence of an isobestic point at 610 nm from spectrophotometric data indicates the presence of Fe 3+ À3,5-DTBC adduct favouring an enzyme-substrate binding phenomenon. Upon stoichiometric addition of 3,5-DTBC pretreated with two equivalents of triethylamine to the iron complex, two catecholate-to-iron(III) ligand-to-metal charge transfer bands (575 and 721 nm) are observed and the in situ generated catecholate intermediate reacts with dioxygen (k obs =9.89 × 10 À4 min À1 ) in ethanol medium to afford exclusively intradiol cleavage products along with a small amount of benzoquinone, and a small amount of extradiol cleavage products, which provide substantial evidence for a substrate activation mechanism.

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Section: Resultsmentioning

confidence: 99%

Catalytic promiscuity of an iron(II)–phenanthroline complex

De¹,

Garai²,

Yadav

et al. 2016

Applied Organom Chemis

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“…However, one of the problems with many current iron-based catalysts is that the substrate must be used in excess, creating issues with process scale-up. In an effort to overcome this, Che and co-workers have reported the use of a variety of iron complexes, previously reported as models for catechol dioxygenase by Krüger and co-workers (73, 74), in conjunction with oxone (peroxymonosulphate) rather than hydrogen peroxide as the oxidant. These complexes were used to oxidize a variety of alkenes with good selectivity for the cis -diol and with excellent conversion on a significant scale (~10g) (Figure 15) (74).…”

Section: Discussionmentioning

confidence: 99%

Mechanism and Catalytic Diversity of Rieske Non-Heme Iron-Dependent Oxygenases

2013

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“…[d] k obs =1 + log(Abs) vs time. [e] k O2 = k obs /[O 2 ], the solubility of O 2 in water, 1.38 × 10 −3 M; in acetonitrile, 8.1 × 10 −3 M and in dichloromethane, 5.8 ×10 −3 M at 25°C. [f] t 1/2 =0.693/ k obs .…”

Section: Resultsmentioning

confidence: 99%

Copper(II)‐Bioinspired Models for Copper Amine Oxidases: Oxidative Half‐Reaction in Water

et al. 2017

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The quinone cofactor is generated at the oxidative half‐reaction of copper amine oxidases (CAO) activity, which is key biogenesis step in biology. The copper(II) complexes [Cu(L1)SO3CF3]SO3CF3, 1; [Cu(L1)ClO4]ClO4, 2 [L1=1,4‐bis[(pyridin‐2‐yl‐methyl)]‐1,4‐diazepane]; [Cu(L2)SO3CF3]SO3CF3, 3 and [Cu(L2)ClO4]ClO4, 4 [L2=1, 4‐bis[2‐(pyridin‐2‐yl)ethyl]‐1,4‐diazepane] were synthesized as models for copper amine oxidases. The molecular structure of complexes was determined by single crystal X‐ray studies and shows distorted square pyramidal geometry (τ, 0.064 ‐ 0.285). The average Cu‐N(2.0 Å) bond distances of model complexes are similar to the Cu‐NHis bond distances in native CAOs enzyme (Cu‐NHis‐456, 2.0‐2.1 Å, Cu‐NHis‐458, 1.9‐2.2 Å and Cu‐NHis‐624,1.9 −2.1 Å).Only one Cu(II)/Cu(I) redox couple (‐0.296 to −0.343 V) was noted in acetonitrile for 1–4 but a well‐defined redox couple around −0.349 to −0.404 V with an additional anodic peak around −0.056 to −0.128 V appeared in the water. The electronic spectra of 1–4 at pH ∼ 6.0 in water, shows ligand‐based absorption band around 260 −264 nm with a shoulder around 290 nm and the d‐d transition appeared around 593–640 nm. Also, an unusual low‐energy transition is centered at 965 nm due to axial field splitting of the eg orbital sets. Interestingly, on raising of the pH solution to ∼7 ‐ 10 instigates a transition of square pyramidal coordination geometry into trigonal bipyramidal for 1–4. This geometrical interconversion is further supported by appearance of two Cu(II)/Cu(I) redox couples around −0.313 to −0.390 V and −0.056 to −0.309 V at pH ranges of ∼7 ‐ 10. All the complexes exhibits almost similar solution EPR parameter (g||, 2.21 ‐ 2.45; A||, 174 ‐ 193 × 10−4 cm−1) to CAO (g||, 2.32; A||, 153×10−4cm−1)5 at 70 K. The model complexes convert substrate 2‐aminophenol into o‐quinone simultaneously using molecular oxygen via oxidative deamination pathway and this formation accomplished by new absorption band at 430 nm with rate of 0.53 ‐ 11.2 ×10−3 s−1 in water. The asymmetric Cu‐Npy bonds and higher distortion in the square pyramidal geometry of 1 and 2 presumed to facilitate geometrical change via decoordination of one the pyridine arms and leads faster dioxygenation reaction than 3 and 4. This decoordinated pyridine arm act as like an acid‐base catalyst to accept and donate protons as in CAO catalysis by amino acid residues at secondary coordination sphere.

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A Highly Reactive and Catalytically Active Model System for Intradiol‐Cleaving Catechol Dioxygenases: Structure and Reactivity of Iron(III) Catecholate Complexes of N,N′‐Dimethyl‐2,11‐diaza[3.3](2,6)pyridinophane

Cited by 106 publications

References 12 publications

Catalytic promiscuity of an iron(II)–phenanthroline complex

Catalytic promiscuity of an iron(II)–phenanthroline complex

Mechanism and Catalytic Diversity of Rieske Non-Heme Iron-Dependent Oxygenases

Copper(II)‐Bioinspired Models for Copper Amine Oxidases: Oxidative Half‐Reaction in Water

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