Structural and electronic properties of 3,4-ethylenedioxythiophene, 3,4-ethylenedisulfanylfurane and thiophene oligomers: A theoretical investigation

We report the results of a series of ab initio and DFT quantum mechanical calculations on the structure and on the electronic spectral of 2,3-ethylenedioxythiophene-, thiophene- and 2,3-ethylenedithiafurane-containing oligomers. Calculations were performed on oligomers formed by n repeating units, where n ranges from 1 to 8. The bond-length alternation patterns in the π-system, the importance of long-range interactions in the stabilization of oligomer chains, the energies of the HOMO and LUMO orbitals and the values of the lowest transition energy have been examined allowing a systematic comparison among the three families of conducting polymers.