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Öğe Molecular Electrocatalysis for Oxygen Reduction by Cobalt Porphyrins Adsorbed at Liquid/Liquid Interfaces(AMER CHEMICAL SOC, 2010) Su, Bin; Hatay, İmren; Trojanek, Antonin; Samec, Zdenek; Khoury, Tony; Gros, Claude P.; Barbe, Jean-Michel; Daina, Antoine; Carrupt, Pierre-Alain; Girault, Hubert H.Molecular electrocatalysis for oxygen reduction at a polarized water/1,2-dichloroethane (DCE) interface was studied, involving aqueous protons, ferrocene (Fc) in DCE and amphiphilic cobalt porphyrin catalysts adsorbed at the interface. The catalyst, (2,8,13,17-tetraethyl-3,7,12,18-tetramethyl-5-p-aminophenylporphyrin) cobalt(II) (CoAP), functions like conventional cobalt porphyrins, activating 02 via coordination by the formation of a superoxide structure. Furthermore, due to the hydrophilic nature of the aminophenyl group, CoAP has a strong affinity for the water/DCE interface as evidenced by lipophilicity mapping calculations and surface tension measurements, facilitating the protonation of the CoAP-O(2) complex and its reduction by ferrocene. The reaction is electrocatalytic as its rate depends on the applied Galvani potential difference between the two phases.Öğe Oxygen and Proton Reduction by Decamethylferrocene in Non-Aqueous Acidic Media(Royal Soc Chemistry, 2010) Su, Bin; Hatay, İmren; Ge, Pei Yu; Mendez, Manuel; Corminboeuf, Clemence; Samec, Zdenek; Ersöz, Mustafa; Girault, Hubert H.Experimental studies and density functional theory (DFT) computations suggest that oxygen and proton reduction by decamethylferrocene (DMFc) in 1,2-dichloroethane involves protonated DMFc, DMFcH(+), as an active intermediate species, producing hydrogen peroxide and hydrogen in aerobic and anaerobic conditions, respectively.Öğe Oxygen Reduction by Decamethylferrocene at Liquid/Liquid Interfaces Catalyzed by Dodecylaniline(Elsevier Science Sa, 2010) Su, Bin; Hatay, İmren; Li, Fei; Partovi-Nia, Raheleh; Mendez, Manuel A.; Samec, Zdenek; Ersöz, Mustafa; Girault, Hubert H.Molecular oxygen (O-2) reduction by decamethylferrocene (DMFc) was investigated at a polarized water/1,2-dichloroethane (DCE) interface. Electrochemical results point to a mechanism similar to the EC type reaction at the conventional electrode/solution interface, in which an assisted proton transfer (APT) by DMFc across the water/DCE interface via the formation of DMFcH(+) corresponds to the electrochemical step and O-2 reduction to hydrogen peroxide (H2O2) represents the chemical step. The proton transfer step can also be driven using lipophilic bases such as 4-dodecylaniline. Finally, voltammetric data shows that lipophilic DMFc can also be extracted to the aqueous acidic phase to react homogeneously with oxygen.Öğe Oxygen Reduction Catalyzed by a Fluorinated Tetraphenylporphyrin Free Base at Liquid/Liquid Interfaces(Amer Chemical Soc, 2010) Hatay, İmren; Su, Bin; Mendez, Manuel A.; Corminboeuf, Clemence; Khoury, Tony; Gros, Claude P.; Bourdillon, Melanie; Meyer, Michel; Barbe, Jean-Michel; Ersöz, Mustafa; Zális, Stanislav; Samec, Zdenek; Girault, Hubert H.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.Öğe Proton-Coupled Oxygen Reduction at Liquid-Liquid Interfaces Catalyzed by Cobalt Porphine(AMER CHEMICAL SOC, 2009) Hatay, Imren; Su, Bin; Li, Fei; Mendez, Manuel Alejandro; Khoury, Tony; Gros, Claude P.; Barbe, Jean-MichelCobalt porphine (COP) dissolved in the organic phase of a biphasic system is used to catalyze O-2 reduction by an electron donor, ferrocene (Fc). Using voltammetry at the interface between two immiscible electrolyte solutions (ITIES), it is possible to drive this catalytic reduction at the interface as a function of the applied potential difference, where aqueous protons and organic electron donors combine to reduce O-2. The current signal observed corresponds to a proton-coupled electron transfer (PCET) reaction, as no current and no reaction can be observed in the absence of either the aqueous acid, COP, c, or O-2.