Co(III) corroles were investigated as efficient catalysts for the reduction of dioxygen in the presence of perchloric acid in both heterogeneous and homogeneous systems. The investigated compounds are (5,10,15-tris(pentafluorophenyl)corrole)cobalt (TPFCor)Co, (10-pentafluorophenyl-5,15-dimesitylcorrole)cobalt (F 5PhMes 2Cor)Co, and (5,10,15-trismesitylcorrole)cobalt (Mes 3Cor)Co, all of which contain bulky substituents at the three meso positions of the corrole macrocycle. Cyclic voltammetry and rotating ring-disk electrode voltammetry were used to examine the catalytic activity of the compounds when adsorbed on the surface of a graphite electrode in the presence of 1.0 M perchloric acid, and this data is compared to results for the homogeneous catalytic reduction of O 2 in benzonitrile containing 10 (-2) M HClO 4. The corroles were also investigated as to their redox properties in nonaqueous media. A reversible one-electron oxidation occurs at E 1/2 values between 0.42 and 0.89 V versus SCE depending upon the solvent and number of fluorine substituents on the compounds, and this is followed by a second reversible one-electron abstraction at E 1/2 = 0.86 to 1.18 V in CH 2Cl 2, THF, or PhCN. Two reductions of each corrole are also observed in the three solvents. A linear relationship is observed between E 1/2 for oxidation or reduction and the number of electron-withdrawing fluorine groups on the compounds, and the magnitude of the substituent effect is compared to what is observed in the case of tetraphenylporphyrins containing meso -substituted C 6F 5 substituents. The electrochemically generated forms of the corrole can exist with Co(I), Co(II), or Co(IV) central metal ions, and the site of the electron-transfer in each oxidation or reduction of the initial Co(III) complex was examined by UV-vis spectroelectrochemistry. ESR characterization was also used to characterize singly oxidized (F 5PhMes 2Cor)Co, which is unambiguously assigned as a Co(III) radical cation rather than the expected Co(IV) corrole with an unoxidized macrocyclic ring.

A novel porphyrin tripod (TPZn(3)) was synthesized via "click chemistry". Three porphyrin moieties of TPZn(3) are geometrically close and linked by a flexible linker. The electron-transfer oxidation of TPZn(3) results in intramolecular pi-dimer formation between porphyrin moieties as indicated by electrochemical, vis-NIR, and ESR measurements. The cyclic voltammogram of TPZn(3) exhibited stepwise one-electron oxidation processes of three porphyrin moieties in the range from 0.58 to 0.73 V (vs SCE in CH(2)Cl(2)). When TPZn(3) was oxidized by tris(2,2'-bipyridyl)-ruthenium(III) ([Ru(bpy)(3)](3+)), the oxidized species (TPZn(3))(n+) (0 < n