Theoretical investigation of the 3,4-ethylenedioxythiophene dimer and unsubstituted heterocyclic derivatives

The molecular geometry, torsional potential, and selected electronic properties (ionization potential and band gap) of the 3,4-ethylenedioxythiophene dimer in both neutral and doped (radical cation) states were investigated using quantum mechanical methods. Calculations were performed using the HF, B3LYP, B3PW91, MPW1PW91, and MP2 methods and the 6-31G(d), 6-31+G(d,p), and 6-311++G(d,p) basis sets. In all cases, calculations on the neutral and radical states were carried out considering the restricted and unrestricted formalisms, respectively. Results have been compared with experimental data when available. Furthermore, five derivatives of the 3,4-ethylenedioxythiophene dimer were built by changing the heteroatoms at both the five- and six-membered rings. Their conformational and electronic properties were studied using B3PW91/ 6-31+G(d,p) calculations. Results indicated that the material generated by interchanging the positions of the oxygen and sulfur atoms with respect to the parent compound presents very promising properties.