Copper N₂S₂ Schiff base macrocycles: The effect of structure on redox potential

Title
Copper N₂S₂ Schiff base macrocycles: The effect of structure on redox potential
Publication Date
2008
Author(s)
Taylor, Michelle K
Trotter, KD
Reglinski, J
Berlouis, LEA
Kennedy, AR
Spickett, CM
Sowden, RJ
Type of document
Journal Article
Language
en
Entity Type
Publication
Publisher
Elsevier BV
Place of publication
Netherlands
DOI
10.1016/j.ica.2008.02.021
UNE publication id
une:8313
Abstract
A series of bis-salicylidene based N₂S₂ copper macrocycles were prepared, structurally characterised and subjected to electrochemical analysis. The aim was to investigate the effects of length of polymethylene chains between either the imine donors or the sulfur donors on redox state and potential of the metal. The complexes structurally characterised had either distorted square planar or tetrahedral geometries depending on their oxidation state (Cu²+ or Cu+, respectively), and the N–(CH₂)n–N bridge was found to be most critical moiety in determining the redox potential and oxidation state of the copper macrocycles, with relatively little change in these properties caused by lengthening the S–(CH₂)n–S bridge from two to three carbons. In fact, a weakness was observed in the complexes at the sulfur donor, as further lengthening of the S–(CH₂)n–S methylene bridge to four carbons caused fission of the carbon–sulfur bond to give dimeric rings and supramolecular assemblies. Cu+ complexes could be oxidised to Cu²+ by tert-butylhydroperoxide, with a corresponding change in the spectrophotometric properties, and likewise Cu²+ complexes could be reduced to Cu+ by treatment with β-mercaptoethylamine. However, repeated redox cycles appeared to compromise the stability of the macrocycles, most probably by a competing oxidation of the ligand. Thus the copper N₂S₂ macrocycles show potential as redox sensors, but further development is required to improve their performance in a biochemical environment.
Link
Citation
Inorganica Chimica Acta, 361(9-10), p. 2851-2862
ISSN
1873-3255
0020-1693
Start page
2851
End page
2862

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