title: Reversible double oxidation and protonation of the non-innocent bridge in a nickel(II) salophen complex.
abstract: Substitution on the aromatic bridge of a nickel(II) salophen complex with electron-donating dimethylamino substituents creates a ligand with three stable, easily and reversibly accessible oxidation states. The one-electron-oxidized product is characterized as a nickel(II) radical complex with the radical bore by the central substituted aromatic ring, in contrast to other nickel(II) salen or salophen complexes that oxidize on the phenolate moieties. The doubly oxidized product, a singlet species, is best described as having an iminobenzoquinone bridge with a vinylogous distribution of bond lengths between the dimethylamino substituents. Protonation of the dimethylamino substituents inhibits these redox processes on the time scale of cyclovoltammetry, but electrolysis and chemical oxidation are consistent with deprotonation occurring concomitantly with electron transfer to yield the mono- and dioxidized species described above.
authors.affiliation: Department of Chemistry and Biochemistry,  Concordia University , Montreal, Quebec H4B 1R6, Canada.
authors.forename: David
authors.initials: D
authors.lastname: de Bellefeuille
authors.forename: Mohammad S
authors.initials: MS
authors.lastname: Askari
authors.forename: Benedikt
authors.initials: B
authors.lastname: Lassalle-Kaiser
authors.forename: Yves
authors.initials: Y
authors.lastname: Journaux
authors.forename: Ally
authors.initials: A
authors.lastname: Aukauloo
authors.forename: Maylis
authors.initials: M
authors.lastname: Orio
authors.forename: Fabrice
authors.initials: F
authors.lastname: Thomas
authors.forename: Xavier
authors.initials: X
authors.lastname: Ottenwaelder
mesh_terms: D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D011522:Protons; D011789:Quantum Theory; D012459:Salicylates / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D011522:Protons; D012459:Salicylates; C090416:salophen; D009532:Nickel