Chiral oligothiophenes for optoelectronic applications: synthesis and spectroscopic study of supramolecular aggregation

Nowadays, conjugated polymers and oligomers are widely used as organic semicon-ductors in optoelectronic devices such as field-effect transistors (OFET), light-emitting diodes (OLED) and solar cells (OPV) [1]; in particular, a very important role in this field has been played by thiophene-based systems. Their optical and electrical properties (structure of absorption bands, fluorescence efficiency, charge and exciton transport, etc.) depend not only on the chemical nature and the conformation assumed, but also on their supramolecular organization in the solid state [2]. The introduction of chiral groups in the chemical structure of conjugated systems represents a valid tool to drive their self-assembly. We shall summarize our recent studies about the supramolecular aggregation for a set of new chiral conjugated oligomers, ad hoc designed and synthesized, consisting of an aromatic central ring (1,4-hydroquinone, 9H-carbazole, 1,4-diketopyrrolo[3,4-c] pyrrole and benzo[1,2-b:4,5-b′]dithiophene-4,8-diol) functionalized with (S)-3,7-dimethyl-1-octyl groups and connected to two 2,2'-bithienyl units (Figure 1).