title: Stable anilinyl radicals coordinated to nickel: X-ray crystal structure and characterization.
abstract: Two anilinosalen and a mixed phenol-anilinosalen ligands involving sterically hindered anilines moieties were synthesized. Their nickel(II) complexes 1, 2, and 3 were prepared and characterized. They could be readily one-electron oxidized (E(1/2)=-0.30, -0.26 and 0.10 V vs. Fc(+)/Fc, respectively) into anilinyl radicals species [1](+), [2](+), and [3](+), respectively. The radical complexes are extremely stable and were isolated as single crystals. X-ray crystallographic structures reveal that the changes in bond length resulting from oxidation do not exceed 0.02 Å within the ligand framework in the symmetrical [1](+) and [2](+). No quinoid bond pattern was present. In contrast, larger structural rearrangements were evidenced for the unsymmetrical [3](+), with shortening of one C(ortho)-C(meta) bond. Radical species [1](+) and [2](+) exhibit a strong absorption band at around 6000 cm(-1) (class III mixed valence compounds). This band is significantly less intense than [3](+), consistent with a rather localized anilinyl radical character, and thus a classification of this species as class II mixed-valence compound. Magnetic and electronic properties, as well as structural parameters, have been computed by DFT methods.
authors.affiliation: Département de Chimie Moléculaire, Chimie Inorganique Redox Biomimétique (CIRE), UMR-5250, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9 (France), Fax: (+33) 476-51-4836.
authors.forename: Amélie
authors.initials: A
authors.lastname: Kochem
authors.forename: Gisèle
authors.initials: G
authors.lastname: Gellon
authors.forename: Nicolas
authors.initials: N
authors.lastname: Leconte
authors.forename: Benoit
authors.initials: B
authors.lastname: Baptiste
authors.forename: Christian
authors.initials: C
authors.lastname: Philouze
authors.forename: Olivier
authors.initials: O
authors.lastname: Jarjayes
authors.forename: Maylis
authors.initials: M
authors.lastname: Orio
authors.forename: Fabrice
authors.initials: F
authors.lastname: Thomas
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005029:Ethylenediamines / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry
chemical_list: D000814:Aniline Compounds; D056831:Coordination Complexes; D005029:Ethylenediamines; D008024:Ligands; D010636:Phenols; D009532:Nickel; C011452:disalicylaldehyde ethylenediamine; C023650:aniline
keywords: X-ray diffraction; aminyl; aniline; ligands; nickel; radicals