Spectroelectrochemical and ESR studies of highly substituted copper corroles

Abstract

Electrochemical and spectroelectrochemical studies are presented for nine copper corroles with electron-withdrawing or electron-donating substituents on the three meso-phenyl rings of the compounds or on the eight β-pyrrole positions of the macrocycle. Up to three reversible oxidations can be seen for each Cu (III) corrole in CH 2 Cl 2 containing 0.1 M TBAP. Unlike the case of ( OEC ) Cu , no dimer is electrochemically detected upon the first oxidation of these compounds at room temperature. However, a dimer forms at low temperature (< -50°C) for compounds having strong electron-donating groups. Two reductions are observed for all nine corroles at low temperature in CH 2 Cl 2, 0.1 M TBAP, but only one reduction is detected at room temperature for four of these compounds which have weak electron-withdrawing or electron-donating groups. The neutral, reduced or oxidized Cu corroles were also characterized by thin-layer UV-visible spectroelectrochemistry and ESR. The resulting data indicates that eight of the nine neutral complexes contain a Cu (III) center while only one complex, [ Br 8( C 6 F 5)3 Cor ] Cu , exists in its Cu (II) form in CH 2 Cl 2 containing 0.2 M TBAP.