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

Michelle K. Taylor, Katherine D. Trotter, John Reglinski, Leonard E.A. Berlouis, Alan R. Kennedy, C.M. Spickett, Rebecca J. Sowden

Research output: Contribution to journalArticle

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 ß-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.

Original languageEnglish
Pages (from-to)2851-2862
Number of pages12
JournalInorganica Chimica Acta
Volume361
Issue number9-10
Early online date16 Feb 2008
DOIs
Publication statusPublished - 27 Jun 2008

Fingerprint

Schiff Bases
imines
Oxidation-Reduction
Copper
Sulfur
copper
sulfur
Carbon
Oxidation
oxidation
carbon
tert-Butylhydroperoxide
Cysteamine
Imines
methylene
assemblies
fission
Metals
Ligands
ligands

Keywords

  • macrocycle
  • copper
  • redox potential
  • geometry
  • donor groups
  • Therapeutics. Pharmacology
  • Pharmacy and materia medica
  • Microbiology

Cite this

Taylor, M. K., Trotter, K. D., Reglinski, J., Berlouis, L. E. A., Kennedy, A. R., Spickett, C. M., & Sowden, R. J. (2008). Copper N2S2 Schiff base macrocycles: the effect of structure on redox potential. Inorganica Chimica Acta, 361(9-10), 2851-2862. https://doi.org/10.1016/j.ica.2008.02.021
Taylor, Michelle K. ; Trotter, Katherine D. ; Reglinski, John ; Berlouis, Leonard E.A. ; Kennedy, Alan R. ; Spickett, C.M. ; Sowden, Rebecca J. / Copper N2S2 Schiff base macrocycles : the effect of structure on redox potential. In: Inorganica Chimica Acta. 2008 ; Vol. 361, No. 9-10. pp. 2851-2862.
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Taylor, MK, Trotter, KD, Reglinski, J, Berlouis, LEA, Kennedy, AR, Spickett, CM & Sowden, RJ 2008, 'Copper N2S2 Schiff base macrocycles: the effect of structure on redox potential', Inorganica Chimica Acta, vol. 361, no. 9-10, pp. 2851-2862. https://doi.org/10.1016/j.ica.2008.02.021

Copper N2S2 Schiff base macrocycles : the effect of structure on redox potential. / Taylor, Michelle K.; Trotter, Katherine D.; Reglinski, John; Berlouis, Leonard E.A.; Kennedy, Alan R.; Spickett, C.M.; Sowden, Rebecca J.

In: Inorganica Chimica Acta, Vol. 361, No. 9-10, 27.06.2008, p. 2851-2862.

Research output: Contribution to journalArticle

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T1 - Copper N2S2 Schiff base macrocycles

T2 - the effect of structure on redox potential

AU - Taylor, Michelle K.

AU - Trotter, Katherine D.

AU - Reglinski, John

AU - Berlouis, Leonard E.A.

AU - Kennedy, Alan R.

AU - Spickett, C.M.

AU - Sowden, Rebecca J.

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N2 - 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 ß-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.

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Taylor MK, Trotter KD, Reglinski J, Berlouis LEA, Kennedy AR, Spickett CM et al. Copper N2S2 Schiff base macrocycles: the effect of structure on redox potential. Inorganica Chimica Acta. 2008 Jun 27;361(9-10):2851-2862. https://doi.org/10.1016/j.ica.2008.02.021