Meso-dichlorophenyl substituted Co(III) corrole: A selective electrocatalyst for the two-electron reduction of dioxygen in acid media, X-ray crystal structure analysis and electrochemistry

A cobalt(III) corrole, represented as ( Cl 2 Ph )3 CorCo ( PPh 3), where ( Cl 2 Ph )3 Cor is the trianion of 5,10,15-tri(2,4-dichlorophenyl)corrole, was synthesized and characterized as to its electrochemical and spectroelectrochemical properties. Single-crystal structure analysis showed the corrole to be monoclinic and have a space group P21/c with α = 13.441(3), b = 28.058(6), c = 27.584(6) Å, α = 90, β = 92.75(3), γ = 90°, Mr = 1144.38, V = 1039.1(4) Å3, Z = 8, Dc = 1.463 mg/cm3, μ = 0.816, F(000) = 4644, R int = 0.0447, R(I > 4σ(I)) = 0.0769, wR(I > 4σ(I)) = 0.2104, R( all data ) = 0.1214 and wR( all data ) = 0.2705. The compound was also examined as a catalyst for the electroreduction of dioxygen when coated on an edge-plane pyrolytic graphite electrode in 1.0 M HClO 4. Cyclic voltammetry and linear sweep voltammetry with a rotating disk electrode (RDE) or a rotating ring disk electrode (RRDE) were utilized to evaluate the catalytic activity of the corrole and elucidate the products of reduction, H 2 O or H 2 O 2. Analysis of the data shows exclusively a two-electron transfer process to give 100% H 2 O 2 as the product and no H 2 O was detectable.