Versatile redox reactivity of triaryl-meso-substituted Ni(II) porphyrin

The electrochemical oxidation of nickel(ii) 5,15-p-ditolyl-10-phenylporphyrin () leads to the formation of different coupling products, with the distribution depending on the nature of the solvent (CH2Cl2-CH3CN, CH2Cl2, DMF), the cell configuration (2 or 3 compartments) and the number of electrons abstracted. In a two compartment configuration (anode and cathode in the same compartment) in a CH2Cl2-CH3CN mixture, nickel(ii) 5-chloro-10,20-p-ditolyl-15-phenylporphyrin () was isolated in good yield and its mechanism of formation is proposed. Switching to the three compartment configuration, the meso-β/meso-β doubly fused dimer () is detected as the major product whereas in pure CH2Cl2, the singly bonded meso-β dimer () is the major product; in both cases a significant amount of is also produced. These results are in accordance with the cyclic voltammetry analysis of measured in CH2Cl2-CH3CN and CH2Cl2 from which the voltammetric trace of is, respectively, appearing or not. In DMF the hydroxyporphyrin was detected as the major product. Furthermore, meso-functionalization of was performed by controlled potential electrolysis with triphenylphosphine as the nucleophile leading to the phosphonium substituted derivative () in good yield. Finally, unprecedented X-ray crystallographic structures of , , and are presented and their respective structural parameters compared.