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 1H 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.