Sensitive Valence Tautomer Equilibrium of Paramagnetic Complexes [(L)Cun+(Qn−)] (n=1 or 2; Q=Quinones) Related to Amine Oxidase Enzymes

Rall, Jochen; Wanner, Matthias; Albrecht, Markus; Hornung, Fridmann M.; Kaim, Wolfgang

doi:10.1002/(sici)1521-3765(19991001)5:10<2802::aid-chem2802>3.0.co;2-5

Cited by 132 publications

(75 citation statements)

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“…The presence of nitrogen (its main isotope 14 N is magnetic) in o-iminoquinones reveals additional information on the spin density distribution in chelate ring. The application of o-iminosemiquinone (as well as o-semiquinone) as a spin label in metal complexes allows one to monitor complex composition, structure and dynamic processes simply by means of EPR spectroscopy [8,[26][27][28][29][30][31].…”

Section: Introductionmentioning

confidence: 62%

Transition metal complexes with bulky 4,6-di-tert-butyl-N-aryl(alkyl)-o-iminobenzoquinonato ligands: Structure, EPR and magnetism

Poddel’sky

Cherkasov

Abakumov

2009

Coordination Chemistry Reviews

325

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Section: Introductionmentioning

confidence: 62%

Transition metal complexes with bulky 4,6-di-tert-butyl-N-aryl(alkyl)-o-iminobenzoquinonato ligands: Structure, EPR and magnetism

Poddel’sky

Cherkasov

Abakumov

2009

Coordination Chemistry Reviews

325

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“…The reaction was monitored by UV/Vis spectroscopy based on the characteristic absorption band of 3,5-DTBQ at λ = 400 nm (ε = 1900 L mol −1 cm −1 ) [42]. 3,5-DTBC-H 2 is well suited for catechol oxidase studies [43,44] due to its stability, low redox potential [45][46][47][48] and the presence of bulky functional groups precluding further reactions. Consequently, it has been used in many model studies of CO as a substrate [49][50][51][52][53][54][55].…”

Section: Catechol Oxidase Activitymentioning

confidence: 99%

Tyrosinase and catechol oxidase activity of copper(I) complexes supported by imidazole-based ligands: structure–reactivity correlations

2016

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Four new imidazole-based ligands, 4-((1H-imidazol-4-yl)methyl)-2-phenyl-4,5-dihydrooxyzole (L OL 1), 4-((1H-imidazol-4-yl)methyl)-2-(tert-butyl)-4,5-dihydrooxyzole (L OL 2), 4-((1H-imidazol-4-yl)methyl)-2-methyl-4,5-dihydrooxyzole (L OL 3), and N-(2,2-dimethylpropylidene)-2-(1-trityl-1H-imidazol-4-yl-)ethyl amine (L imz 1), have been synthesized. The corresponding copper(I) complexes [Cu(I)(L OL 1)(CH3CN)]PF6 (CuL OL 1), [Cu(I)(L OL 2)(CH3CN)]PF6 (CuL OL 2), [Cu(I)(L OL 3)(CH3CN)]PF6 (CuL OL 3), [Cu(I)(L imz 1)(CH3CN)2]PF6 (CuL imz 1) as well as the Cu(I) complex derived from the known ligand bis(1-methylimidazol-2-yl)methane (BIMZ), [Cu(I)(BIMZ)(CH3CN)]PF6 (CuBIMZ), are screened as catalysts for the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC-H2) to 3,5-di-tert-butylquinone (3,5-DTBQ). The primary reaction product of these oxidations is 3,5-di-tert-butylsemiquinone (3,5-DTBSQ) which slowly converts to 3,5-DTBQ. Saturation kinetic studies reveal a trend of catalytic activity in the order CuL OL 3 ≈ CuL OL 1 > CuBIMZ > CuL OL 2 > CuL imz 1. Additionally, the catalytic activity of the copper(I) complexes towards the oxygenation of monophenols is investigated. As substrates 2,4-di-tert-butylphenol (2,4-DTBP-H), 3-tert-butylphenol (3-TBP-H), 4-methoxyphenol (4-MeOP-H), N-acetyl-L-tyrosine ethyl ester monohydrate (NATEE) and 8-hydroxyquinoline are employed. The oxygenation products are identified and characterized with the help of UV/Vis and NMR spectroscopy, mass spectrometry, and fluorescence measurements. Whereas the copper complexes with ligands containing combinations of imidazole and imine functions or two imidazole units (CuL imz 1 and CuBIMZ) are found to exhibit catalytic tyrosinase activity, the systems with ligands containing oxazoline just mediate a stoichiometric conversion. Correlations between the structures of the complexes and their reactivities are discussed.

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“…The equilibrium depends of course on auxiliary ligands as shown in the case of copper catecholate complexes, whereas soft ligands prefer the lower oxidation state of the metal ion. [42] A similar behaviour with (nitropropane)iron complexes is also to be expected as a key step in these oxygenations. Further work is in progress on the design and elucidation of iron-containing functional 2-nitropropane dioxygenase models.…”

Section: Kinetic Measurementsmentioning

confidence: 99%

Kinetics and Mechanism of the Copper-Catalysed Oxygenation of 2-Nitropropane

Balogh-Hergovich

Gréczi

Kaizer

et al. 2002

Eur. J. Inorg. Chem.

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Primary and secondary nitro compounds react with dioxygen in the presence of copper metal and N ligands such as N,N,NЈ,NЈ-tetramethylethylenediamine (tmeda), 2,2Ј-bipyridine (bpy), and 1,10-phenantroline (phen) in various solvents to form aldehydes or ketones. More coordinating solvents as well as donor N ligands accelerate the reaction remarkably. The oxygenolysis of 2-nitropropane (NPH) in the presence of copper and tmeda in DMF results in acetone and acetone oxime. The amount of tmeda influences the chemoselectivity, higher tmeda concentrations preferentially lead to the formation of the oxime. The kinetics of the reaction, measured at 90°C, resulted in a rate equation of first-order dependence on copper and dioxygen and second-order dependence on 2-nitropropane. The rate constant, activation

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Sensitive Valence Tautomer Equilibrium of Paramagnetic Complexes [(L)Cun+(Qn−)] (n=1 or 2; Q=Quinones) Related to Amine Oxidase Enzymes

Cited by 132 publications

References 0 publications

Transition metal complexes with bulky 4,6-di-tert-butyl-N-aryl(alkyl)-o-iminobenzoquinonato ligands: Structure, EPR and magnetism

Transition metal complexes with bulky 4,6-di-tert-butyl-N-aryl(alkyl)-o-iminobenzoquinonato ligands: Structure, EPR and magnetism

Tyrosinase and catechol oxidase activity of copper(I) complexes supported by imidazole-based ligands: structure–reactivity correlations

Kinetics and Mechanism of the Copper-Catalysed Oxygenation of 2-Nitropropane

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