Bioinspired Trispyrazolylborato Nickel(II) Flavonolate Complexes and Their Reactivity Toward Dioxygen

Hoof, Santina; Limberg, Christian

doi:10.1002/zaac.201800457

Cited by 10 publications

(5 citation statements)

References 28 publications

(17 reference statements)

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“…ATR-infrared (IR) spectra were recorded on a Bruker alpha FTIR spectrometer in the region 4000−400 cm −1 using solid samples. Microanalyses were performed on a HEKAtech Euro EA 3000 elemental analyzer (we have frequently experienced that Tp complexes lead to C analysis, which are a little bit too low, while the other elements fit 33 ). The presence of dichloromethane in the elemental analysis samples was confirmed using 1 H NMR spectroscopy.…”

Section: ■ Conclusionmentioning

confidence: 99%

The Behavior of Trispyrazolylborato-Metal(II)-Flavonolate Complexes as Functional Models for Bacterial Quercetinase—Assessment of the Metal Impact

Hoof

Limberg

2019

Inorg. Chem.

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A series of five compounds Tp Mes MFla (Tp Mes = hydrotris(3-mesityl)pyrazolylborate; M = Mn, Fe, Co, Ni, Zn; Fla = 3-hydroxyflavonolate) has been synthesized as models for the 2,4-quercetin dioxygenase, QueD. The structures have been determined and the complexes proved to be isomorphous. Considering the structures more closely revealed that they differ in the degree of delocalization in the chelate ring formed through the binding of the two O donors of the flavonolate to the metal center, which is also supported by the results of UV−vis and IR spectroscopic investigations. The resulting trend (Zn/Fe > Co > Mn > Ni) is, however, not in line with the one that was found investigating the redox properties of the complexes by cyclic voltammetry (Zn > Fe > Ni > Co > Mn). Notably, from CV clear-cut information could be derived, as the complexes exhibited exceptionally wellbehaved quasi-reversible redox transitions, indicating that the Tp ligand stabilizes the flavonolate radical formed in the oxidation process rather well. The fact that the rates, with which the complexes react with O 2 in DMF solution, correlate with the position of the flavonolate redox couples, suggest that these reactions proceed via the initial electron transfer from the flavonolate to O 2 . After the O 2 reaction, salicylic acid was identified as one of the products, the formation of which can be explained by the hydrolysis of the depside that should form upon a dioxygenation similar to the QueD enzyme-catalyzed reaction. 18 O labeling experiments confirmed the presence of O 2 derived O atoms. Mechanistic inferences based on the above results are discussed.

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Section: ■ Conclusionmentioning

confidence: 99%

The Behavior of Trispyrazolylborato-Metal(II)-Flavonolate Complexes as Functional Models for Bacterial Quercetinase—Assessment of the Metal Impact

Hoof

Limberg

2019

Inorg. Chem.

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“…ATR‐IR spectra were recorded with a Bruker alpha FTIR spectrometer in the region 4000–400 cm −1 . Microanalyses were performed with a HEKAtech Euro EA 3000 elemental analyzer (we have frequently experienced that Tp complexes lead to C analyses, which are a little bit too low, while the results for the other elements fit) [54] . UV‐vis spectra were obtained at variable temperatures with an Agilent 8453 UV‐vis spectrophotometer equipped with a Unisoku USP‐203‐A cryostat.…”

Section: Methodsmentioning

confidence: 99%

The Properties of Hydrotris(3‐mesitylpyrazol‐1‐yl) Borate Iron(II) Complexes with Aryl Carboxylate Co‐ligands – Stabilization of an Iron(III) Alkylperoxide

Müller

Baturin

Hoof

et al. 2021

Zeitschrift anorg allge chemie

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Through the reaction of [TpMesFeCl] with different benzoic acids, namely salicylic acid (HOBzo−OH), m‐chloro benzoic acid (HOBzm−Cl), p‐dimethylamino benzoic acid (OBzp−N(Me)2) and benzoic acid itself, in the presence of triethylamine corresponding complexes [TpMesFeOBzR] with varying residues R could be isolated and fully characterized (including paramagnetic NMR spectroscopy, elemental analysis, IR, cyclic voltammetry). From acetonitrile solutions they crystallized as acetonitrile adducts [TpMesFe(NCMe)OBzR], which indicates, that a coordination and activation of an exogeneous substrate is principally possible. While no reactivity towards O2 could be observed, in contact with tBuOOH all complexes were found to form iron(III) tert‐butylperoxide complexes [TpMesFe(OBzR)(OOtBu)], as evidenced by UV‐vis, EPR and Raman spectroscopy. Through UV‐vis studies it was shown, that both the formation rate and the stability of [TpMesFe(OBzR)(OOtBu)] are influenced by the basicity of the benzoate co‐ligands, which is determined by the substituents. An extraordinarily high stability was observed for the salicylate representative, which, however, cannot be explained on basis of such electronic effects; other potential stabilizing factors that may play an important role are discussed.

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“…ATR‐IR spectra of solid samples were recorded with a Bruker alpha FTIR spectrometer in the region 4000–400 cm −1 . Microanalyses were performed with a HEKAtech Euro EA 3000 elemental analyzer (we have frequently experienced that Tp complexes lead to C analyses, which are a little bit too low, while the results for the other elements fit) [68] . UV‐vis spectra were obtained at variable temperatures with an Agilent 8453 UV‐vis spectrophotometer equipped with a Unisoku USP‐203‐A cryostat.…”

Section: Methodsmentioning

confidence: 99%

Versatile Coordination Behavior of the Asymmetric Bis(3‐mesityl‐pyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl) Hydroborate Ligand towards Late 3 d M²⁺ Ions

et al. 2020

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Bearing in mind the potential which tris(pyrazolyl) hydroborate ligands have demonstrated in various different fields of coordination chemistry, the behavior of a more rarely employed representative, namely bis(3‐mesitylpyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl) hydroborate (TpMes,H*), towards a series of divalent metal ions has been investigated. Thus, the synthesis of two new heteroleptic metal chlorido [TpMes,H*MCl] complexes, 2, (Mn2+, 2‐a, and Cu2+, 2‐e) are described, which correspond to the typical precursor compounds that would be needed for subsequent research. Structural and spectroscopic properties of the two new and four published members of this series (M=Fe2+, 2‐b, Co2+, 2‐c, Ni2+, 2‐d, Zn2+, 2‐f) are discussed in detail for the solid and solution states. Furthermore, synthetic routes to five homoleptic [(TpMes,H*)2M] complexes, 3, bearing Mn2+, 3‐a, Fe2+, 3‐b, Co2+, 3‐c, Ni2+, 3‐d, and Cu2+, 3‐e, ions as well as an alternative preparation method for [(κ2‐TpMes,H*)2Zn], 3‐f, are described. Their structures and spectroscopic parameters are compared to those of their heteroleptic counterparts. Additionally, the complex [(TpH,Mes*)2Cu], 4, is reported, representing the second example of a complex with the (3‐mesitylpyrazol‐1‐yl)bis(5‐mesitylpyrazol‐1‐yl) hydroborate ligand (TpH,Mes*).

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Bioinspired Trispyrazolylborato Nickel(II) Flavonolate Complexes and Their Reactivity Toward Dioxygen

Cited by 10 publications

References 28 publications

The Behavior of Trispyrazolylborato-Metal(II)-Flavonolate Complexes as Functional Models for Bacterial Quercetinase—Assessment of the Metal Impact

The Behavior of Trispyrazolylborato-Metal(II)-Flavonolate Complexes as Functional Models for Bacterial Quercetinase—Assessment of the Metal Impact

The Properties of Hydrotris(3‐mesitylpyrazol‐1‐yl) Borate Iron(II) Complexes with Aryl Carboxylate Co‐ligands – Stabilization of an Iron(III) Alkylperoxide

Versatile Coordination Behavior of the Asymmetric Bis(3‐mesityl‐pyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl) Hydroborate Ligand towards Late 3 d M²⁺ Ions

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Bioinspired Trispyrazolylborato Nickel(II) Flavonolate Complexes and Their Reactivity Toward Dioxygen

Cited by 10 publications

References 28 publications

The Behavior of Trispyrazolylborato-Metal(II)-Flavonolate Complexes as Functional Models for Bacterial Quercetinase—Assessment of the Metal Impact

The Behavior of Trispyrazolylborato-Metal(II)-Flavonolate Complexes as Functional Models for Bacterial Quercetinase—Assessment of the Metal Impact

The Properties of Hydrotris(3‐mesitylpyrazol‐1‐yl) Borate Iron(II) Complexes with Aryl Carboxylate Co‐ligands – Stabilization of an Iron(III) Alkylperoxide

Versatile Coordination Behavior of the Asymmetric Bis(3‐mesityl‐pyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl) Hydroborate Ligand towards Late 3 d M2+ Ions

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Versatile Coordination Behavior of the Asymmetric Bis(3‐mesityl‐pyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl) Hydroborate Ligand towards Late 3 d M²⁺ Ions