Electrochemistry of Innocent Cyanocobalt Corroles

The electrochemical and spectroscopic properties of numerous transition metal corroles have been examined under a wide variety of solution conditions with particular interest being placed on the innocent or non-innocent nature of the corrole macrocycle and oxidation state of the central metal ion. The innocence of the redox active corrole ligand, as well as the half-wave potentials and sites of electron transfer are known to be strongly influenced by the type of central metal ion, degree of axial coordination (i.e. four-, five- or six-coordinate) and type of peripheral substituents at the meso or β-pyrrole positions of the corrole ligand. Our laboratories have previously investigated five- and six-coordinate cobalt corroles with P, N or O donor ligands and a wide variety of peripheral corrole substituents. In this work, we describe the intriguing electrochemical and spectroscopic properties of several innocent cobalt(III) corroles which are axially ligated by two pyridine molecules, one or two cyanide ions or one pyridine and one cyanide ion. Examples of the investigated corroles are shown in Chart 1 and represented as [(R)3CorCo(Py)2], [(R)3CorCo(Py)(CN)]-, [(R)3CorCo(CN)]- and [(R)3CorCo(CN)2]2- where (R)3Cor is the corrole macrocycle and R is one of several meso-substituents.