Synthesis and electrochemical reactivity of σ-bonded and N-substituted cobalt porphycenes

The first synthesis and characterization of sigma-bonded and N-substituted cobalt porphycenes is reported. The investigated compounds are represented as (Pc)Co(R) and (N-CH3OEPc)CoCl, where R is CH3 or C6H5, Pc is the dianion of 2,3,6,7,12,13,16,17-octaethylporphycene (OEPc), 2,7,12,17-tetrapropylporphycene (TPrPc), or 2,7 12,17-tetraethyl-3,6,13,16-tetramethylporphycene (EtioPc), N-CH3OEPc is the monoanion of N-methyl-2,3,6,7, 12,13,16,17-octaethylporphycene. Each sigma-bonded (Pc)Co(R) derivative can be reversibly reduced or oxidized by two electrons, but a slow migration of the cr-bonded R group occurs following electrogeneration of [(Pc)Co(R)](+.) leading, as a final product, to an N-substituted cobalt(II) porphycene which is also electroactive and undergoes two reductions in PhCN. The singly reduced product of this reaction is formulated as a Co(II) pi-anion radical which undergoes a slow "back-migration" of the CH3 group to regenerate (OEPc)Co(CH3).