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Issue 20, 2017
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Control of structure, stability and catechol oxidase activity of copper(II) complexes by the denticity of tripodal platforms

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Abstract

Copper(II) complexes of a new polydentate tripodal ligand trenpyz (L, tris[2-(5-pyrazolylmethyl)aminoethyl]amine) were characterized in both solution and solid states. A combined evaluation of potentiometric UV-Vis and EPR data provided both thermodynamic and structural information on the complexes formed in solution. In equimolar solution the highly stable square pyramidal CuHL and trigonal bipyramidal CuL are the dominant species at around pH 3 and 5–8, respectively. Above pH 8 further deprotonation was observed (pK = 9.56), which is related to the formation of a copper(II)-bound pyrazolate anion. This creates the possibility for the formation of oligonuclear complexes, through pyrazolate bridges, and at a 3/2 Cu(II)/L ratio three trinuclear complexes were identified, similar to the copper(II)–tachpyz (N,N′,N′′-tris(5-pyrazolylmethyl)-1,3,5-cis,cis-triamino-cyclohexane) system studied earlier. The trinuclear complexes of the two ligands have considerably different speciations, due to the different denticities of tripodal platforms. At the optimal pH the catechol oxidase activities of the triply deprotonated trinuclear complexes of trenpyz and tachpyz are similar, but the pH-rate constant profiles are significantly different, as a consequence of the deviations in their speciation. Consequently, the H2dtbc oxidation promoted by these trinuclear complexes can be easily controlled by the denticity of the tripodal ligands, since it affects the coordination environment of the central metal ion, which is proposed to be the main actor during the reaction.

Graphical abstract: Control of structure, stability and catechol oxidase activity of copper(ii) complexes by the denticity of tripodal platforms

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Publication details

The article was received on 06 Jun 2017, accepted on 20 Aug 2017 and first published on 22 Aug 2017


Article type: Paper
DOI: 10.1039/C7NJ02013A
Citation: New J. Chem., 2017,41, 11647-11660
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    Control of structure, stability and catechol oxidase activity of copper(II) complexes by the denticity of tripodal platforms

    F. Matyuska, N. V. May, A. Bényei and T. Gajda, New J. Chem., 2017, 41, 11647
    DOI: 10.1039/C7NJ02013A

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