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- Title
Sequential Phenolate Oxidations in Octahedral Cobalt(III) Complexes with [N<sub>2</sub>O<sub>3</sub>] Ligands.
- Authors
Allard, Marco M.; Xavier, Fernando R.; Heeg, Mary Jane; Schlegel, H. Bernhard; Verani, Cláudio N.
- Abstract
Three six-coordinate cobalt(III) complexes containing electron-rich phenolato pentadentate [N2O5] ligands were synthesized and characterized, namely, [CoIII(L1)(MeOH)] ( 1), [CoIII(L2)(MeOH)] ( 2) and [CoIII(L3)(MeOH)] ( 3), where L1, L2 and L3 are the triply deprotonated, triply negative form of( E)-6,6′-[({2-[(3,5-di- tert-butyl-2-hydroxybenzylidene)amino]phenyl}azanediyl)bis(methylene)]bis(2,4-di- tert-butylphenol), ( E)-6,6′-[({3-[(3,5-di- tert-butyl-2-hydroxybenzylidene)amino]naphthalen-2-yl}azanediyl)bis(methylene)]bis(2,4-di- tert-butylphenol) and ( E)-6,6′-[({2-[(2-hydroxy-3-methoxybenzylidene)amino]phenyl}azanediyl)bis(methylene)]bis(2,4-di- tert-butylphenol), respectively. Crystal structures were obtained for 1- 3 and reveal a hexacoordinate cobalt(III) ion bound to the [N2O3] donors of each ligand and a methanol molecule occupying the sixth position. The complexes exhibited comparable electronic behavior dominated by phenolate→cobalt charge transfer processes and four redox-accessible states involving three distinct phenolato/phenoxyl radical couples and a fourth process associated with the CoII/CoIII couple. The redox processes were cycled 30 times without major decomposition at the surface of the electrode for 1 and 2, indicating that the oxidized species should be substitutionally inert and do not degrade significantly upon cycling. Electronic-structure DFT calculations on models 1′ and 2′ favor the generation of localized phenoxyl radicals and suggest distinctive oxidation sequences associated to the nature of the ligands.
- Subjects
COBALT compounds synthesis; PHENOXIDES; LIGANDS (Chemistry); CRYSTAL structure research; CHARGE transfer; OXIDATION-reduction reaction
- Publication
European Journal of Inorganic Chemistry, 2012, Vol 2012, Issue 29, p4622
- ISSN
1434-1948
- Publication type
Article
- DOI
10.1002/ejic.201200171