Porphyrin-Based Hole Conducting Electropolymer

The monomer 5-(4-aminophenyl)-10,20-bis(2,4,6-trimethylphenyl)porphyrin was synthesized and found to electropolymerize on platinum, indium tin oxide, and other electrodes to form a clear, semiconducting film with strong absorption in the visible spectral region. The linear, hole-conducting polymer has a unique structure, with porphyrin units linked to one another through the 5-(4-aminophenyl) nitrogen atom and the carbon atom at the 15-position on the macrocyclic ring. The porphyrin macrocyclic ring is thus an integral part of the linear polymer backbone. The oxidation potential of the film is 0.85 V and the reduction potential is −1.12 V vs SCE. The absorption spectrum of the film resembles that of a monomeric model porphyrin, but with significant peak broadening. Streak camera studies of the fluorescence of the polymer yield a lifetime of 15 ps, indicating strong quenching of the porphyrin first excited singlet state relative to that of the monomer. The properties of the polymer suggest that it may be useful in sensors, catalysts, and solar energy conversion devices.