title: Redox properties of a mononuclear copper(II)-superoxide complex.
abstract: Redox properties of a mononuclear copper(II) superoxide complex, (L)Cu(II)-OO(•), supported by a tridentate ligand (L = 1-(2-phenethyl)-5-[2-(2-pyridyl)ethyl]-1,5-diazacyclooctane) have been examined as a model compound of the putative reactive intermediate of peptidylglycine α-hydroxylating monooxygenase (PHM) and dopamine β-monooxygenase (DβM) (Kunishita et al. J. Am. Chem. Soc. 2009, 131, 2788-2789; Inorg. Chem. 2012, 51, 9465-9480). On the basis of the reactivity toward a series of one-electron reductants, the reduction potential of (L)Cu(II)-OO(•) was estimated to be 0.19 ± 0.07 V vs SCE in acetone at 298 K (cf. Tahsini et al. Chem.-Eur. J. 2012, 18, 1084-1093). In the reaction of TEMPO-H (2,2,6,6-tetramethylpiperidine-N-hydroxide), a simple HAT (hydrogen atom transfer) reaction took place to give the corresponding hydroperoxide complex LCu(II)-OOH, whereas the reaction with phenol derivatives ((X)ArOH) gave the corresponding phenolate adducts, LCu(II)-O(X)Ar, presumably via an acid-base reaction between the superoxide ligand and the phenols. The reaction of (L)Cu(II)-OO(•) with a series of triphenylphosphine derivatives gave the corresponding triphenylphosphine oxides via an electrophilic ionic substitution mechanism with a Hammett ρ value as -4.3, whereas the reaction with thioanisole (sulfide) only gave a copper(I) complex. These reactivities of (L)Cu(II)-OO(•) are different from those of a similar end-on superoxide copper(II) complex supported by a tetradentate TMG3tren ligand (1,1,1-Tris{2-[N(2)-(1,1,3,3-tetramethylguanidino)]ethyl}amine (Maiti et al. Angew. Chem., Int. Ed. 2008, 47, 82-85).
authors.affiliation: Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University , 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Tano
authors.forename: Yuri
authors.initials: Y
authors.lastname: Okubo
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kunishita
authors.forename: Minoru
authors.initials: M
authors.lastname: Kubo
authors.forename: Hideki
authors.initials: H
authors.lastname: Sugimoto
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Fujieda
authors.forename: Takashi
authors.initials: T
authors.lastname: Ogura
authors.forename: Shinobu
authors.initials: S
authors.lastname: Itoh
mesh_terms: D003300:Copper / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D013481:Superoxides / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D013481:Superoxides; D003300:Copper