Oxygen reduction catalyzed by a fluorinated tetraphenylporphyrin free base at liquid/liquid interfaces.
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.
Hatay
Imren
I
Laboratoire d'Electrochimie Physique et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland.
Su
Bin
B
Méndez
Manuel A
MA
Corminboeuf
Clémence
C
Khoury
Tony
T
Gros
Claude P
CP
Bourdillon
Mélanie
M
Meyer
Michel
M
Barbe
Jean-Michel
JM
Ersoz
Mustafa
M
Zális
Stanislav
S
Samec
Zdenek
Z
Girault
Hubert H
HH
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*
D005025:Ethylene Dichlorides; D005296:Ferrous Compounds; D000075163:Metallocenes; D011166:Porphyrins; D014867:Water; C024565:ethylene dichloride; D010100:Oxygen; C004998:ferrocene