Electrochemical Synthesis of Conducting Polyporphyrin Films based on 5,10,15,20-Tetrakis(4-hydroxyphenyl)porphyrin

A hydroxy-substituted tetraphenylporphyrin was oxidatively electropolymerized from its solutions in ethanol by cyclic voltammetry. The electropolymerization process is investigated using cyclic voltammetry, absorption spectroscopy, and electrochemical quartz crystal microbalance. The results of IR and electronic absorption spectroscopy studies show that, in deposition from ethanol, the polymerization occurs via the O−H group of the phenyl substituent, which results in the formation of C−O−C bonds. The mechanism of polyporphyrin formation is similar to polymerization of simple organic compounds. The deposited polyporphyrin film (thickness of 80 nm) has a smooth surface. Using the Mott−Schottky approach, it was establish that the films have hole conductivity (i.e., they are a p-type semiconductor). The flat band potential of the poly-5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin is 0.33 V. The film is further oxidized in a supporting electrolyte solution by applying positive potentials, with anions of the supporting electrolyte incorporating into the polyporphyrin.