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The diprotonated form of a fluorinated free base porphyrin, 5-(p-aminophenol)-10,15,20-tris(pentafluorophenyl)porphyrin ([H.sub.2]FAP), has catalyzed the reduction of oxygen by a weak electron donor like ferrocene (Fc). Spectrophotometric measurements performed in 1,2-dichloroethane solutions have shown that reduction of oxygen by Fc catalyzed by [H.sub.4][FAP.sup.2+] has occurred in the presence of the tetrakis(pentafluorophenyl)borate ([TB.sup.-]) counteranion in the organic phase.

Laser flash photolysis measurements are utilized to examine the dynamics of photoinduced electron transfer from the singlet excited state of porphyrin tripod (TP[Zn.sub.3]) to pyridine moiety (Py[C.sub.60]). The efficient intracomplex photoinduced electron transfer in TP[Zn.sub.3]-Py[C.sub.60] in nonpolar solvents is attributed to the [pi]-[pi] interactions between the porphyrin and fullerene moieties, together with intramolecular [pi]-bond formation between the porphyrin radical cation and the neutral porphyrin in TP[Zn.sub.3.sup.*+].

Molecular electrocatalysis for oxygen reduction at a polarized water/1,2-dichloroethane (DCE) interface is analyzed, which has involved aqueous protons, ferrocene (Fc) in DCE and amphiphilic cobalt porphyrin catalysts adsorbed at the interface. The reaction is shown to be electrocatalytic as its rate has depended on the applied Galvani potential difference between the two phases.

Cobalt porphine (CoP) dissolved in the organic phase of a biphasic system is used for catalyzing [O.sub.2] reduction by an electron donor, ferrocene (Fc). Voltammetry is used at the interface between two immiscible electrolyte solutions (ITIES) to drive this catalytic reduction at the interface as a function of the applied potential difference, where aqueous protons and organic electron donors have combined to reduce [O.sub.2].

The diprotonated form ofafluorinated free base porphyrin, namely 5-(p-aminophenyl)-10,15,20tris(pentafluorophenyl)porphyrin (H2FAP), 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 H4FAP2+ is observed by UV-vis spectroscopy and ion-transfer voltammetry, due to the double protonation of H2FAP at the imino nitrogen atoms in the tetrapyrrole ring. H4FAP2+ 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 H4FAP2+ 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 H4FAP2+ on oxygen. [ABSTRACT FROM AUTHOR]

A novel porphyrin tripod (TPZn3) was synthesized via "click chemistry". Three porphyrin moieties of TPZn3 are geometrically close and linked by a flexible linker. The electron-transfer oxidation of TPZn3 results in intramolecular π-dimer formation between porphyrin moieties as indicated by electrochemical, vis-NIR, and ESR measurements. The cyclic voltammogram of TPZn3 exhibited stepwise one-electron oxidation processes of three porphyrin moieties in the range from 0.58 to 0.73 V (vs SCE in CH2CI2). When TPZn3 was oxidized by tris(2,2'-bipyridyl)-ruthenium(lll) ([Ru(bpy)3]3+), the oxidized species (TPZn3)n+(0 < n ⩽ 3) exhibited a charge resonance band in the NIR region due to the r-dimer formation between porphyrin moieties. A supramolecular electron donor-acceptor system was also constructed using TPZn3. The flexible conformation of TPZn3 makes it possible to capture a fullerene derivative containing a pyridine moiety (PyC60) inside the cavity by π-.π interactions as well as the coordination bond between Zn2+ and the pyridine moiety. The formation of a 1:1 supramolecular complex of TPZn3 with PyC60 (TPZn3-PyC60) was indicated in the UV-vis and 1H NMR spectra in nonpolar solvents. The association constant of TPZn3 with PyC60 (1.1 x 105 M-1 in toluene) is much larger as compared with those of the corresponding monomer (MPZn) and dimer porphyrin (DPZn2). The dynamics of photoinduced electron transfer from the singlet excited state of TPZn3 to PyC60 was examined by laser flash photolysis measurements. The efficient intracomplex photoinduced electron transfer in TPZn3-PyC60 occurred in nonpolar solvents, resulting from the π-π interactions between the porphyrin and fullerene moieties, together with intramolecular v-bond formation between the porphyrin radical cation and the neutral porphyrin in TPZn3∙+. [ABSTRACT FROM AUTHOR]

Three series of cobalt(lll) corroles were tested as catalysts for the electroreduction of dioxygen to water. One was a simple monocorrole represented as (Me4Ph5Cor)Co, one a face-to-face biscorrole linked by an anthracene (A), biphenylene (B), 9,9-dimethylxanthene (X), dibenzofuran (O) or dibenzothiophene (S) bridge, (BCY)Co2 (with Y = A, B, X, O or S), and one a face-to-face bismacrocyclic complex, (PCY)Co2, containing a Co(ll) porphyrin and a Co(lll) corrole also linked by one of the above rigid spacers (Y = A, B, X, or O). Cyclic voltammetry and rotating ring-disk electrode voltammetry were both used to examine the catalytic activity of the cobalt complexes in acid media. The mixed valent Co(ll)/Co(lll) complexes, (PCY)Co2, and the biscorrole complexes, (BCY)Co2, which contain two Co(lll) ions in their air-stable forms, all provide a direct four-electron pathway for the reduction of O2 to H2O in aqueous acidic electrolyte when adsorbed on a graphite electrode, with the most efficient process being observed in the case of the complexes having an anthracene spacer. A relatively small amount of hydrogen peroxide was detected at the ring electrode in the vicinity of E½ which was located at 0.47 V vs SCE for (PCA)Co2 and 0.39 V vs SCE for (BCA)Co2. The cobalt(Ill) monocorrole (Me4Ph5Cor)Co also catalyzes the electroreduction of dioxygen at E½ = 0.38 V with the final products being an approximate 50% mixture of H2O2 and H2O. [ABSTRACT FROM AUTHOR]