title: Ligand contributions to the electronic structures of the oxidized cobalt(II) salen complexes.
abstract: Square planar cobalt(II) complexes of salen ligands N,N'-bis(3-tert-butyl-5R-salicylidene)-1,2-cyclohexanediamine), where R = OMe (1) and tert-butyl (2), were prepared. 1 and 2 were electrochemically reversibly oxidized into cations [1-H(2)O](+) and [2-H(2)O](+) in CH(2)Cl(2). The chemically generated [1-H(2)O](SbF(6))·0.68 H(2)O·0.82CH(2)Cl(2) and [2-H(2)O](SbF(6))·0.3H(2)O·0.85CH(2)Cl(2) were characterized by X-ray diffraction and NIR spectroscopy. Both complexes are paramagnetic species containing a square pyramidal cobalt ion coordinated at the apical position by an exogenous water molecule. They exhibit remarkable NIR bands at 1220 (7370 M(-1) cm(-1)) and 1060 nm (5560 M(-1) cm(-1)), respectively, assigned to a CT transition. DFT calculations and magnetic measurements confirm the paramagnetic (S = 1) ground spin state of the cations. They show that more than 70% of the total spin density in [1-H(2)O](+) and [2-H(2)O](+) is localized on the metal, the remaining spin density being distributed over the aromatic rings (30% phenoxyl character). In the presence of N-methylimidazole 1 and 2 are irreversibly oxidized by air into the genuine octahedral cobalt(III) bis(phenolate) complexes [1-im(2)](+) and [2-im(2)](+), the former being structurally characterized. Neither [1-im(2)](+) nor [2-im(2)](+) exhibits a NIR feature in its electronic spectrum. 1 and 2 were electrochemically two-electron oxidized into [1](2+) and [2](2+). The cations were identified as Co(III)-phenoxyl species by their characteristic absorption band at ca. 400 nm in the UV-vis spectrum. Coordination of the phenoxyl radical to the cobalt(III) metal ion is evidenced by the EPR signal centered at g = 2.00.
authors.affiliation: Equipe de Chimie Inorganique Redox Biomimétique, Département de Chimie Moléculaire, Université Joseph Fourier, 38041 Grenoble Cedex 9, France.
authors.forename: Amélie
authors.initials: A
authors.lastname: Kochem
authors.forename: Hussein
authors.initials: H
authors.lastname: Kanso
authors.forename: Benoit
authors.initials: B
authors.lastname: Baptiste
authors.forename: Himanshu
authors.initials: H
authors.lastname: Arora
authors.forename: Christian
authors.initials: C
authors.lastname: Philouze
authors.forename: Olivier
authors.initials: O
authors.lastname: Jarjayes
authors.forename: Hervé
authors.initials: H
authors.lastname: Vezin
authors.forename: Dominique
authors.initials: D
authors.lastname: Luneau
authors.forename: Maylis
authors.initials: M
authors.lastname: Orio
authors.forename: Fabrice
authors.initials: F
authors.lastname: Thomas
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D004563:Electrochemistry; D004583:Electrons; D005029:Ethylenediamines / Q000737:chemistry*; D008024:Ligands; D008752:Methylene Chloride / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction
chemical_list: D005029:Ethylenediamines; D008024:Ligands; D009942:Organometallic Compounds; D003035:Cobalt; D008752:Methylene Chloride; C011452:disalicylaldehyde ethylenediamine