Electronic and Spectroscopic Properties of Thiophene-based Organic Polyconjugated Semiconductors Built from Inherently Chiral Monomers

The availability of materials which could couple electroactivity properties and enantiorecognition capability is an ambitious objective of the modern chemical research. Chirality is generally introduced in these materials by attaching chiral pendants to an electroactive polyconjugated backbone through suitable linkers and a great variety of substituents have been employed either chosen from the chiral pool, like sugar and amino-acids, or man-made, designed and synthesized for specific applications. We have developed a new strategy for preparing electroactive chiral polymers, consisting in the oxidative polymerization of chiral oligothiophene monomers in which chirality results from a tailored torsion produced along the oligothiophene backbone by an atropisomeric bithiophene or bipyrrole scaffold (Scheme 1).1 The structural design of the monomers requires that the biheteroaromatic core could take part in the conjugative communication between the bithiophene termini. Furthermore, the polymerization sites of the monomers should be homotopic, thus granting the perfect constitutional regularity of the polymers. The 2,2'-bis(2,2'-bithiophene-5-yl)-3,3'-bithianaphthene and the 1,1'-dimethyl-3,3'-bis(2,2'-bithiophene-5-yl)- 2,2'-biindole are the first examples of this strategy. The antipodes have been obtained in an enantiopure state and submitted to the electropolymerization process yielding materials exhibiting outstanding chirality manifestations.