Polarons and bipolarons in poly(tri-heterocycle) based on furan and thiophene

A theoretical analysis of polarons and bipolarons in poly(OSO) is presented. Singly and doubly oxidized oligomers (3<n<15), whose all rings are linked at the syn or anti-forms, are used as model. The PM3 calculations showed that the single positive charge is concentrated around linked furan rings. Furthermore, a quinoid structure extends over 6 (oxidized) and 8 (doubly oxidized) rings. The UV-vis absorption spectra, simulated with the aid of the ZINDO/S-CI method, indicated two and one sub-gap absorption peaks for the syn and anti-conformation oligomers, respectively. These results might provide a coherent interpretation of the experimental spectra of doped polyfuran and polythiophene.