On the π-stacking of oxidized thiophene oligomers

The formation of stable π-stacked dimers constituted by thiophene-containing molecules in the radical cation state has been investigated using different theoretical methods. Calculations on systems formed by two thiophenes and two 2,2′-bithiophenes, where the two molecules of each dimer are oxidized, provided one and two π-stacked complexes, respectively. The molecular geometry and electronic properties of the molecules within each complex have been analyzed and compared with those calculated for the isolated molecule. Furthermore, the effect of dimerization on lowest π–π∗ transition energy has been examined and related with the inter-molecular delocalization of π-electrons in thiophene-containing doped systems.