Issue 20, 2017

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

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

Supplementary files

Article information

Article type
Paper
Submitted
06 Jun 2017
Accepted
20 Aug 2017
First published
22 Aug 2017
This article is Open Access
Creative Commons BY license

New J. Chem., 2017,41, 11647-11660

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

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements