Electrosynthesis and Characterization of Symmetrical and Unsymmetrical Linear Porphyrin Dimers and Their Precursor Monomers

The electrochemical synthesis of linear symmetrical octaethylporphyrin−octaethylporphyrin and unsymmetrical tetraphenylporphyrin−octaethylporphyrin dimeric porphyrins with one viologen as a spacer and of their precursor porphyrin monomers is reported. The mechanism of the electrochemical substitution leading to the dimeric porphyrins is discussed. These new compounds have been characterized by 1 H NMR, UV−vis spectroscopy, FAB mass spectroscopy, and microanalysis. Electrochemical data are reported, and the redox behavior is analyzed for the monomers and the dimers in terms of π−π interactions between the two porphyrin centers. ESR measurements were carried out on the unsymmetrical Cu−Zn and Cu−Cu dimeric metalloporphyrins which displayed intermolecular metal interactions.