The electrochemical oxidation of zinc(II) 5,15-p-ditolyl-10-phenylporphyrin at its first oxidation potential leads to the formation of the corresponding meso-meso porphyrin dimer as the main product. The number of electrons abstracted, the addition of the hindered base 2,6-lutidine as well as operating in DMF, instead of a CH(2)Cl(2)/CH(3)CN mixture are the key parameters to obtain high yields of the desired coupling product. Indeed, when the electrolyses are carried out in the CH(2)Cl(2)/CH(3)CN mixture, the unexpected zinc(II) 5-chloro-10,20-p-ditolyl-15-phenyl porphyrin is produced as a by-product, the chlorine atom originating from the CH(2)Cl(2) solvent. The monomer and the dimer are characterised by electrochemical analysis. The signature of the dimer is clearly distinguished on the cyclic voltammogram of the monomer on condition of the prior addition of 2,6-lutidine as a hindered base, indicating that the dimerisation process is thus strongly accelerated. Besides, unprecedented X-ray crystallographic structures of the monomer and the meso-meso dimer are presented and their respective structural parameters are compared.

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.