Equilibria and tyrosinase activity of a dinuclear and its analogous tetranuclear imidazolate-bridged copper(II) complexes

Alves, Wendel A.; Bagatin, Izilda A.; Ferreira, Ana Maria da Costa

doi:10.1016/s0020-1693(01)00490-x

Cited by 34 publications

(30 citation statements)

References 36 publications

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“…The [Cu(apip)imH] 2ϩ complex exhibited a pH-dependent equilibrium with the corresponding dinuclear species, which seems to react subsequently with molecular oxygen. This dinuclear complex, [Cu 2 (apip) 2 im] 3ϩ , was later isolated in the solid state as perchlorate salt, and actually was shown to catalyze the oxidation of phenolic substrates by molecular oxygen, described elsewhere [8].…”

Section: Imine Copper(ii) Complexes Have Been Extensivelymentioning

confidence: 99%

Factorial design analysis of the catalytic activity of di‐imine copper(II) complexes in the decomposition of hydrogen peroxide

Alves

Azzellini

Ferreira

et al. 2001

Int J of Chemical Kinetics

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Factorial design analysis was applied to the study of the catalytic activity of diimine copper(II) complexes, in the decomposition of hydrogen peroxide. The studied complexes show a tridentate imine ligand (apip), derived from 2-acetylpyridine and 2-(2-aminoethyl)pyridine, and a hydroxo or an imidazole group at the fourth coordination site of the copper ion. The factorial design models for both [Cu(apip)imH] 2ϩ and [Cu(apip)OH] ϩ were similar. Increasing the peroxide concentration from 3.2 ϫ 10 Ϫ3 to 8.1 ϫ 10 Ϫ3 mol L Ϫ1 resulted in increased oxygen formation. Increasing the pH from 7 to 11 also increased oxygen formation and had an effect about twice as large as the peroxide one. Both complexes also had an important interaction effect between peroxide concentration and pH. However, increasing the catalyst concentration led to a decrease in total oxygen formation. The obtained results were corroborated by further data, achieved by using the usual univariate method, and helped to elucidate equilibrium steps occurring in the studied systems. In very alkaline solutions, the studied [Cu(apip)imH] 2ϩ complex can form the corresponding dinuclear species, [Cu 2 (apip) 2 im] 3ϩ . While the mononuclear complex proved to be an efficient catalyst in hydrogen peroxide decomposition, the corresponding dinuclear compound seemed to be able to coordinate with the dioxygen molecule, inhibiting its observed release.

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Section: Imine Copper(ii) Complexes Have Been Extensivelymentioning

confidence: 99%

Factorial design analysis of the catalytic activity of di‐imine copper(II) complexes in the decomposition of hydrogen peroxide

Alves

Azzellini

Ferreira

et al. 2001

Int J of Chemical Kinetics

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“…We have reported 10 an imidazole-bridged dinuclear copper(II) compound with a tridentade imine ligand that efficiently catalyzes the aerobic oxidation of 2,6-di-tertbutylphenol, in methanolic solution, and also of 3,4-dihydroxyphenylalanine (L-dopa) in aqueous solution, in the pH range of 7-11. This complex coexists in aqueous solution with the corresponding mono-and tetranuclear compounds, depending on the pH, and the catalytic activity increases from the mono-to the tetranuclear species.…”

Section: Introductionmentioning

confidence: 99%

“…11 In that work, it was shown that differences in the geometrical features of the ligands can bring about a varied reactivity of the metal centre, based on differences in the hydrophobicity of the complexes, accessibility of the substrate to the metal ion due to steric bulk of the ligand, and the extent of the steric match between the substrate and the complex. 10,11 Another predominant factor on determining the catalytic activity of these complexes studied is the stability of the dinuclear moiety in solution. Further, since these complexes are frequently used as precursors of more elaborated polinuclear species, the distribution of the various complexes in solution is essential to obtain different desired frameworks.…”

Section: Introductionmentioning

confidence: 99%

Equilibria and catalytic properties of a chloro-bridged Diimine copper(II) complex in the N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) oxidation

Alves¹,

Almeida-Filho²,

Santos³

et al. 2004

J. Braz. Chem. Soc.

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2 Cl 2 ]X 2 ·nH 2 O preparada como sais perclorato 3, nitrato 4 e cloreto 5, respectivamente, foram isoladas e caracterizadas por técnicas espectroscópicas (UV/Vis, IV e EPR). O composto 2 teve sua estrutura determinada por cristalografia de raios-X. Em solventes não-aquosos predomina a espécie dinuclear, enquanto em solução aquosa, ou solventes contendo água, um equilíbrio entre a espécie dinuclear e a mononuclear 1 foi observado. Estudos cinéticos, em metanol, da oxidação catalisada de TMPD indicaram uma dependência de primeira-ordem da velocidade inicial com a concentração de catalisador e um efeito de saturação com aumento da concentração de substrato. O composto dinuclear é mais reativo que o mono-, e experimentos adicionais mostraram que o contra-íon cloreto afeta significativamente os parâmetros cinéticos, deslocando o equilíbrio envolvendo as espécies 2 e 5, além de estabilizar um par iônico com o substrato.Some new copper(II) complexes with a tridentate imine ligand, bimpy (or 2-(benzimidazolyl)methylene-2-amino-1-ethylpyridine), were prepared, and had their catalytic activity in the N,N,N´,N´-tetramethyl-p-phenylenediamine (TMPD) oxidation compared. Mononuclear species, [Cu(bimpy)(H 2 O) 2 ](NO 3 ) 2 , (1) and [Cu(bimpy)Cl 2 ]·H 2 O, (2), as well as the dinuclear species containing chloro-bridges, [Cu 2 (bimpy) 2 Cl 2 ]X 2 ·nH 2 O as perchlorate 3, nitrate 4 and chloride 5 salts, respectively, were obtained and characterized by different techniques (UV/Vis, IR, EPR and X-ray crystallography). In non-aqueous solvents, the dinuclear species predominates; however, in aqueous solution or solvents containing water, equilibrium between dinuclear and correlated mononuclear species 1 was verified. Kinetic studies, in methanol solution, on the catalyzed TMPD oxidation indicated a first-order dependence of the initial rate with the catalyst concentration, and a saturation effect with increasing concentrations of the substrate. The dinuclear species was observed to be more reactive than the mononuclear one, and further experiments showed that the counter-ion chloride can significantly affect the kinetic parameters, mostly by shifting the mono-/dinuclear equilibrium, and stabilizing an ion-pair with the substrate.Keywords: copper(II) complexes, dinuclear species, equilibria, kinetics, catalytic activity IntroductionCopper complexes containing diimines have been extensively studied, and reported as good models for a variety of enzymes associated to the molecular oxygen metabolism. 1 Additionally some of them were used to construct exotic molecular architectures, sensitize photoelectrochemical cells, label biomaterials as the basis for selective sensors, and also to obtain new magnetic materials. 2 Copper-containing active sites are responsible, in vivo, for the catalyzed oxidation of phenols, and amines, where two-electron transfer occurs between the substrate and two metal centres, as in tyrosinase and catechol oxidases, 3 or 873 Equilibria and Catalytic Properties of a Chloro-Bridged Diimine Copper(II) Complex V...

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“…The oxidation of DTBP by molecular dioxygen in the methanol solution of these Cu(II) complexes gave similar yield of PQ to that characteristic for tyrosinase [26,27].…”

Section: Introductionmentioning

confidence: 66%

Oxidation of 2,6-di-tert-butylphenols to Diphenoquinones Catalysed by Schiff Base-Cu(II) Systems Immobilized on Polymer Support

2006

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Benzoquinone, diphenoquinones and its derivatives are important intermediates for industrial synthesis of a wide variety of special chemicals, such as pharmaceuticals, dyes and agricultural chemicals. The useful catalyst were obtained by aminolysis of vinylbenzyl chloride/divinylbenzene copolymer with ethylenediamine (1) or urotropine (2) and then modification by salicylaldehyde (1A, 2A) or picolinaldehyde (1B, 2B). The catalytic activity of Cu(II) complexes with Schiff base immobilized on the synthesized supports were tested in the oxidation reaction of 2,6-di-tert-butylphenol (DTBP) to diphenoquinone (PQ) with tertbutylhydroperoxide. The best oxidation degree of DTBP (60-70%) and the selectivity towards PQ (80%) is revealed by Cu(II) complexes with long Schiff base ligands derived from salicylaldimine (1A), which have CuL structure (EPR measurement).

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Equilibria and tyrosinase activity of a dinuclear and its analogous tetranuclear imidazolate-bridged copper(II) complexes

Cited by 34 publications

References 36 publications

Factorial design analysis of the catalytic activity of di‐imine copper(II) complexes in the decomposition of hydrogen peroxide

Factorial design analysis of the catalytic activity of di‐imine copper(II) complexes in the decomposition of hydrogen peroxide

Equilibria and catalytic properties of a chloro-bridged Diimine copper(II) complex in the N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) oxidation

Oxidation of 2,6-di-tert-butylphenols to Diphenoquinones Catalysed by Schiff Base-Cu(II) Systems Immobilized on Polymer Support

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