A chiroptical study of chiral Λ- and X- type oligothiophenes toward modelling the interchain interactions of chiral conjugated polymers

A variety of chiral Lambda-type and X-type oligothiophenes (MDC 1-10) was synthesized and studied by means of UV-vis and CD spectroscopy in order to model the chiral interchain interactions of conjugated polymers with optically Active side chains in both neutral and oxidized state. It was found that, within the class of chiral Lambda-type oligothiophenes, the interchain chiral exciton coupling was only present when using an electronwithdrawing imine linkage between the oligothiophene and the chiral unit (MDC 7-9). Together with the observed decrease in g-value (dissymmetry factor for absorption) by extending the oligothiophene moiety, these linkage and elongation restrictions impose crucial drawbacks on chiral Lambda-type oligothiophenes as study model in both neutral and oxidized state. Therefore, a new chiral X-type oligothiophene (MDC 10) was developed that combines chiral exciton coupling in neutral state with the additional ability of oxidation.