title: Oxygen reduction catalyzed by a fluorinated tetraphenylporphyrin free base at liquid/liquid interfaces.
abstract: The diprotonated form of a fluorinated free base porphyrin, namely 5-(p-aminophenyl)-10,15,20-tris(pentafluorophenyl)porphyrin (H(2)FAP), can catalyze the reduction of oxygen by a weak electron donor, namely ferrocene (Fc). At a water/1,2-dichloroethane interface, the interfacial formation of H(4)FAP(2+) is observed by UV-vis spectroscopy and ion-transfer voltammetry, due to the double protonation of H(2)FAP at the imino nitrogen atoms in the tetrapyrrole ring. H(4)FAP(2+) is shown to bind oxygen, and the complex in the organic phase can easily be reduced by Fc to produce hydrogen peroxide as studied by two-phase reactions with the Galvani potential difference between the two phases being controlled by the partition of a common ion. Spectrophotometric measurements performed in 1,2-dichloroethane solutions clearly evidence that reduction of oxygen by Fc catalyzed by H(4)FAP(2+) only occurs in the presence of the tetrakis(pentafluorophenyl)borate (TB(-)) counteranion in the organic phase. Finally, ab initio computations support the catalytic activation of H(4)FAP(2+) on oxygen.
authors.affiliation: Laboratoire d'Electrochimie Physique et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Imren
authors.initials: I
authors.lastname: Hatay
authors.forename: Bin
authors.initials: B
authors.lastname: Su
authors.forename: Manuel A
authors.initials: MA
authors.lastname: Méndez
authors.forename: Clémence
authors.initials: C
authors.lastname: Corminboeuf
authors.forename: Tony
authors.initials: T
authors.lastname: Khoury
authors.forename: Claude P
authors.initials: CP
authors.lastname: Gros
authors.forename: Mélanie
authors.initials: M
authors.lastname: Bourdillon
authors.forename: Michel
authors.initials: M
authors.lastname: Meyer
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Barbe
authors.forename: Mustafa
authors.initials: M
authors.lastname: Ersoz
authors.forename: Stanislav
authors.initials: S
authors.lastname: Zális
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Samec
authors.forename: Hubert H
authors.initials: HH
authors.lastname: Girault
mesh_terms: D002384:Catalysis; D005025:Ethylene Dichlorides / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry; D000075163:Metallocenes; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011166:Porphyrins / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry*
chemical_list: D005025:Ethylene Dichlorides; D005296:Ferrous Compounds; D000075163:Metallocenes; D011166:Porphyrins; D014867:Water; C024565:ethylene dichloride; D010100:Oxygen; C004998:ferrocene