ABSTRACT
In principle, the electrochemical method offers an advantage for the con struction of molecular electronic wires because electroactive polymers can grow directly on the terminal electrode. The electrochemical polymerization of metalloporphyrin derivatives was reported for the first time by Macor and Spiro [22]. In this study, electroactive porphyrin films obtained by the electroinitiated cationic vinyl polymerization of metalloprotoporphyrins were investigated as modified electrodes. As for synthetic porphyrin, Murray et al. reported electroactive porphyrin films obtained by the electro-oxidative coupling of a peripheral aromatic amine of tetra(o-aminophenyl)porphyrin [23]. Then, electrochemical polymerization was applied to various mesosubstituted metalloporphyrins, and various modified electrodes of porphy rin polymers were constructed and investigated [24]. For the purposes of electrochemical polymerization, porphyrin derivatives should have periph eral coupling units such as vinyl, aniline, phenol, or pyrrole, which form bridges by oxidative coupling. However, none of the polymers obtained from porphyrin derivatives were linear, but they were cross-linked amorph ous polymers without an ordered structure. For the construction of an ordered structure toward a molecular wire, coupling units should be designed carefully. Although the coupling position reported at that time was on per ipheral meso or pyrrole-/? substituents, coupling toward the axial position and direct coupling without a bridge should be taken into account for an ordered structure. Furthermore, the coupling units in previous studies were not functional units but only bridges. Since coupling units are similar to precursors of the conducting polymer [25], they should be used for a molecular wire or donor-acceptor unit. With this in mind, we tried to con struct a one-dimensional ordered structure of the porphyrin polymer by the electrochemical method.
