Fused ring pyrrole polymers

Oyama et al. [227,228] electrochemically polymerized fused ring pyrroles in acetonitrile solutions to form brown-black polymer films. The monomers were... 

Several fused-ring systems containing pyrrole units have been electropolymerized. [3,2- >]pyrrolopyrrole (66) is oxidized at the same potential of dipyrrole producing a polymer film with the characteristics of polypyrrole [307] with the exception of the low conductivity (5 x 10 S cm ). Also the isomer [2,3-6]pyrrolopyrrole (67) [308] polymerizes at oxida-... 

In order to increase the redox potential of PP, the two terminal pyrrole units were fused onto a central benzene ring, as in 13, 14, and 15 [217-220], and onto a pyrazine ring, as in 16 [221,222] the presence of an aromatic nucleus involved in quinoid structures in the final doped polymer should increase the E° value of the polymer. This hypothesis has been nicely verified by experiment. Polymers originating from 13-16 are all stable in air and conductivity is maintained at reasonable levels, even if somewhat reduced in comparison with PP. 

It may seem surprising that the E° value of the polymer derived from 16 is lower than that of the polymer from 13. In fact pyrazine, onto which the pyrrole units are fused in 16, is a much more electron-poor (7r-deficient) system than a benzene ring however, it should be considered that the aromaticity of the pyrazine... 

A series of fused two-ring systems (77) containing pyrrole, thiophene and selenophene rings has been investigated [329,330]. Of these only the 3,2- systems polymerize to conjugated polymers since only their conjugation pattern allows an effective delocalization. The conductivity of the doped materials is, in any case, low (5 X 10 S cm ). 

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