Sequential Phenolate Oxidations in Octahedral Cobalt(III) Complexes with [N 2 O 3 ] Ligands
| Autor: | Fernando R. Xavier, Marco M. Allard, H. Bernhard Schlegel, Mary Jane Heeg, Cláudio N. Verani |
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| Rok vydání: | 2012 |
| Předmět: | |
| Zdroj: | European Journal of Inorganic Chemistry. 2012:4622-4631 |
| ISSN: | 1099-0682 1434-1948 |
| DOI: | 10.1002/ejic.201200171 |
| Popis: | 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 phenolatecobalt 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. |
| Databáze: | OpenAIRE |
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