ISSN:
1432-1327
Keywords:
Key words Galactose oxidase
;
Biomimetic model
;
Copper
;
Free radical
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Copper(II) complexes derived from the tripodal ligand bis(3′-t–butyl-2′-hydroxybenzyl)(2-pyridylmethyl)amine (LH2) have been studied in order to mimic the redox active site of the free radical-containing copper metalloenzyme galactose oxidase. In non-coordinating solvents such as dichloromethane, only an EPR-silent dimeric complex was obtained (L2Cu2). The crystal structure of L2Cu2 revealed a "butterfly" design of the [Cu(μOR)2Cu] unit, which is not flattened and leads to a short Cu–Cu distance, the t–butyl groups being localized on the same side of the [Cu(μOR)2Cu] unit. The dimeric structure was broken down by acetonitrile or by alcohols, leading quantitatively to a brown mononuclear copper(II) complex. UV-visible and EPR data indicated the coordination of the solvent in these mononuclear complexes. Electrochemical as well as chemical (silver acetate) one-electron oxidation of acetonitrile solutions of the monomeric complex led to a yellow-green solution. Based on EPR, UV-visible and resonance Raman spectroscopy, the one-electron oxidation product was identified as a cupric phenoxyl radical system. It slowly decomposes into a product where the ligand has been substituted (dimerization) in the para position of the hydroxyl group, for one of the phenolic groups. The data for the one-electron oxidized species provides strong evidence for a free-radical copper (II) complex.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s007750050105
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