CoIII and CuII complexes of reduced Schiff bases: Generation of phenoxyl radical species

Fabrice Thomas, Himanshu Arora, Christian Philouze, Olivier Jarjayes

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30 Scopus citations


The three complexes [CoIIIL1Cl] (1), [Co IIIL2]+·ClO4- (2+·ClO4-), and [CuIIH 2L2]2+·2ClO4- (H232+·2ClO4-) [where H 2L1 = N,N′-dimethyl-N,N′-bis(2-hydroxy-3,5-di- tert-butylbenzyl)ethylenediamine, H2L2 = N,N′-bis(2-pyridylmethyl)-N,N′-bis(2-hydroxy-3,5-di-tert- butylbenzyl)ethylenediamine] have been prepared. The bis-phenolate and bis-phenol complexes, 2+ and H232+ respectively, have been characterized by X-ray diffraction, showing a metal ion within an elongated octahedral geometry. 1-2 exhibit in their cyclic voltammetry curves two anodic reversible waves attributed to the successive oxidation of the phenolates into phenoxyl radicals. The cobalt radical species (1) +, (2)2+, and (2)3+ have been characterized by combined UV-Vis and EPR spectroscopies. In the presence of one equivalent of base, one phenolic arm of H232+ is deprotonated and coordinates the metal. The resulting complex (H3+) exhibits a single reversible redox wave at ca. 0.3 V. The electrochemically generated oxidized species is EPR silent and exhibits the typical features of a radical compound, with absorption bands at 411 and 650 nm. The fully deprotonated complex 3 is obtained by addition of two equivalents of nBu4N+OH - to H232+. It exhibits a new redox wave at a lower potential (-0.16 V), in addition to the wave at ca. 0.3 V. We assigned the former to the one-electron oxidation of the uncoordinated phenolate into an unstable phenoxyl radical.

Original languageEnglish
Pages (from-to)3122-3130
Number of pages9
JournalInorganica Chimica Acta
Issue number12
StatePublished - 15 Oct 2010
Externally publishedYes


  • Biomimetic chemistry
  • Coordinated radical
  • Galactose oxidase
  • Phenoxyl
  • Reduced schiff bases


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