Synthesis, structure and catecholase activity study of dinuclear copper(II) complexes †

Reim, Jörg; Krebs, Bernt

doi:10.1039/a704245k

Cited by 250 publications

(164 citation statements)

References 33 publications

(10 reference statements)

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“…The two isosbestic points at 581 and 785 nm indicate the presence of only two absorbing species in solution. These marked changes are consistent with previously observed UV/Vis spectral changes upon titration of dinuclear copper(II) complexes with tetrachlorocatechol [2,28,29] and indicate binding of the catechol to the complex.…”

Section: Wwwchemeurjorgsupporting

confidence: 79%

Oxidative Double Dehalogenation of Tetrachlorocatechol by a Bio‐Inspired Cu^II Complex: Formation of Chloranilic Acid

Bruijnincx

Viciano‐Chumillas

Lutz

et al. 2008

Chemistry A European J

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Copper(II) complexes of the potentially tripodal N,N,O ligand 3,3‐bis(1‐methylimidazol‐2‐yl)propionate (L1) and its conjugate acid HL1 have been synthesised and structurally and spectroscopically characterised. The reaction of equimolar amounts of ligand and CuII resulted in the complexes [Cu(L1)]n(X)n (X=OTf−, PF6−; n=1,2), for which a new bridging coordination mode of L1 is inferred. Although these complexes showed moderate catecholase activity in the oxidation of 3,5‐di‐tert‐butylcatechol, surprising reactivity with the pseudo‐substrate tetrachlorocatechol was observed. A chloranilato‐bridged dinuclear CuII complex was isolated from the reaction of [Cu(L1)]n(PF6)n with tetrachlorocatechol. This stoichiometric oxidative double dehalogenation of tetrachlorocatechol to chloranilic acid by a biomimetic copper(II) complex is unprecedented. The crystal structure of the product, [Cu2(ca)Cl2(HL1)2], shows a bridging bis‐bidentate chloranilato (ca) ligand and ligand L1 coordinated as its conjugate acid (HL1) in a tridentate fashion. Magnetic susceptibility studies revealed weak antiferromagnetic coupling (J=−35 cm−1) between the two copper centres in the dinuclear complex. Dissolution of the green complex [Cu2(ca)Cl2(HL1)2] resulted in the formation of new pink‐purple mononuclear compound [Cu(ca)(HL1)(H2O)], the crystal structure of which was determined. It showed a terminal bidentate chloranilato ligand and N,N‐bidentate coordination of ligand HL1, which illustrates the flexible coordination chemistry of ligand L1.

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Section: Wwwchemeurjorgsupporting

confidence: 79%

Oxidative Double Dehalogenation of Tetrachlorocatechol by a Bio‐Inspired Cu^II Complex: Formation of Chloranilic Acid

Bruijnincx

Viciano‐Chumillas

Lutz

et al. 2008

Chemistry A European J

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“…Usually, the catecholase activity of model complexes is largely attributed to the distance Cu … Cu, but other effects such as redox potentials, neighboring groups, and the individual coordination spheres can play important roles. 66 For complexes 1 and 2, the Cu … Cu distances are very similar (Table 2) and may not be the reason for their different activities. Since the first step in the proposed mechanism is the oxidation of one substrate molecule coupled to a two-electron reduction of …”

Section: Catechol Oxidationmentioning

confidence: 89%

“…Kinetic parameters for complexes 1 and 2 the active site, 67 it was expected that complex 1 presented higher activity than complex 2, which has a more negative reduction potential, but this kind of correlation has been questioned. 66 The non-reversibility shown in the voltammograms of complex 1 indicates that, after reduction, the complex integrity is not maintained in solution and this can be a reason of its lower reactivity. On the other hand, the reversibility shown by complex 2 at high scan rates shows that this complex does not decompose as fast as complex 1 after reduction, leading to its higher reactivity.…”

Section: Catechol Oxidationmentioning

confidence: 99%

Binuclear CuII complexes as catalysts for hydrocarbon and catechol oxidation reactions with hydrogen peroxide and molecular oxygen

Martins¹,

Souza²,

Fernandez³

et al. 2010

J. Braz. Chem. Soc.

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Dois ligantes tridentados, HL1, [(2-hidroxibenzil)(2-(imidazol-2-il)etil)]amina, e HL2, [(2-hidroxibenzil)(2-(piridil-2-il)etil]amina, foram usados na síntese dos complexos binucleares [Cu 2 (L1) 2 ]Cl 2• 2H 2 O, complexo 1, e [Cu 2 (L2) 2 ] (ClO 4 ) 2• 1.5H 2 O, complexo 2, para serem empregados como catalisadores em processos de oxidação. Os complexos foram caracterizados por análise elementar e espectroscopias na região do infravermelho, ultravioleta-visível e ressonância paramagnética eletrônica. Foram também estudados por voltametria cíclica e titulação potenciométrica, a fim de caracterizar seus comportamentos em solução. A resolução da estrutura cristalina do complexo 1 mostrou um cátion binuclear contendo dois grupos fenóxido em ponte. Este arranjo possui uma distância Cu … Cu de 3.043(10) Å, similar à observada na catecol oxidase (2.90 Å). Os comportamentos catalíticos destes complexos foram investigados nas oxidações de cicloexano e de catecol. Na oxidação de cicloexano observou-se baixa atividade para ambos os complexos, que pode ser atribuída ao estereoimpedimento produzido pela falta de coplanaridade entre os anéis aromáticos do arcabouço dos ligantes, sugerindo que a aproximação entre o substrato e o centro ativo binuclear é uma etapa determinante no mecanismo da reação. Com relação à atividade de catecolase, foram observadas altas eficiências, com o complexo 2 sendo mais ativo que o complexo 1. Isto indica que o ligante piridina é capaz de estabilizar melhor o intermediário proposto para esse processo, que contém o centro Cu • 1.5H 2 O, complex 2, in order to obtain catalysts for oxidative processes. Both complexes were characterized by elemental analysis, IR, UV-Vis and EPR spectroscopies. In addition, they were studied by cyclic voltammetry and potentiometric titration in order to investigate their behavior in solution. The crystal structure of complex 1 revealed a binuclear cation where the metal centers are bridged by two phenoxo groups. This arrangement provides a Cu … Cu distance of 3.043(10) Å, which is similar to the observed for catechol oxidase (2.90 Å). The catalytic reactivities of both complexes were investigated for hydrocarbon and catechol oxidations. Complexes 1 and 2 led to low overall hydrocarbon oxidation conversion values of 6.34 % and 7.15 %, respectively. However, for complex 1, only cyclohexanol (Cy-OH) and cyclohexanone (Cy=O) were isolated as reaction products, with selectivities of 68.1% for Cy-OH. This low overall conversion is tentatively attributed to steric hindrance effects produced by the non-coplanar aromatic rings of the ligand scaffolds, which suggest that the access of the hydrocarbon molecule to the binuclear active center is a determinant step in the reaction mechanism. Investigation of catecholase activities has shown high efficiencies, with complex 2 being more active than complex 1. It indicates that the pyridine-containing ligand is able to stabilize the intermediate Cu I Cu I center which is proposed to be formed in this process. This is corroborated by t...

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“…observed from Cu 4 L 4 is comparable to those with moderate to high catecholase activities. [8][9][10][11][12][13][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] It is noticeable that the four copper ions are non-coupled in Cu 4 L 4 whereas most model complexes with high catecholase activities are di-or tri-nuclear copper …”

Section: Resultsmentioning

confidence: 99%

Tetrameric Self-Assembly of a Cu(II) Complex Containing Schiff-Base Ligand and Its Unusually High Catecholase-like Activity

Sarkar¹,

Lee²,

Hong³

et al. 2013

Bulletin of the Korean Chemical Society

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We report a new tetrameric supramolecular Cu(II) complex (Cu 4 L 4 = tetrakis(N,N'-bis(salicylidene)-2,2'-ethylenedianiline)Copper(II)) with a Schiff-base ligand (H 2 L = N,N'-bis (salicylaldimine)-1,2-ethylenediamine) containing two N,O-bidentate chelate groups. Though the copper sites of Cu 4 L 4 are non-coupled, the complex exhibits a unsually high catecholase-like activity (k cat = 935 h −1 ) when the Cu 4 L 4 solution is treated with 3,5-di-tert-butylcatechol (3,5-DTBC) at basic condition in the presence of air. Combined information obtained from UV-VIS and EPR measurements could lead the suggestion of the reaction pathway in which the substrate may bind to Cu(II) ions by anti-anti didentate bridging mode.

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Synthesis, structure and catecholase activity study of dinuclear copper(II) complexes †

Cited by 250 publications

References 33 publications

Oxidative Double Dehalogenation of Tetrachlorocatechol by a Bio‐Inspired Cu^II Complex: Formation of Chloranilic Acid

Oxidative Double Dehalogenation of Tetrachlorocatechol by a Bio‐Inspired Cu^II Complex: Formation of Chloranilic Acid

Binuclear CuII complexes as catalysts for hydrocarbon and catechol oxidation reactions with hydrogen peroxide and molecular oxygen

Tetrameric Self-Assembly of a Cu(II) Complex Containing Schiff-Base Ligand and Its Unusually High Catecholase-like Activity

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Synthesis, structure and catecholase activity study of dinuclear copper(II) complexes †

Cited by 250 publications

References 33 publications

Oxidative Double Dehalogenation of Tetrachlorocatechol by a Bio‐Inspired CuII Complex: Formation of Chloranilic Acid

Oxidative Double Dehalogenation of Tetrachlorocatechol by a Bio‐Inspired CuII Complex: Formation of Chloranilic Acid

Binuclear CuII complexes as catalysts for hydrocarbon and catechol oxidation reactions with hydrogen peroxide and molecular oxygen

Tetrameric Self-Assembly of a Cu(II) Complex Containing Schiff-Base Ligand and Its Unusually High Catecholase-like Activity

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Oxidative Double Dehalogenation of Tetrachlorocatechol by a Bio‐Inspired Cu^II Complex: Formation of Chloranilic Acid

Oxidative Double Dehalogenation of Tetrachlorocatechol by a Bio‐Inspired Cu^II Complex: Formation of Chloranilic Acid