Conformational Transitions in Chiral, Gallic Acid-Functionalized Poly(dithienopyrrole): A Comparative UV−vis and CD Study

Abstract

An achiral and chiral poly(dithieno[3,2-b:2′,3′-d]pyrrole) (PDTP), substituted with a gallic acid-derived moiety, was prepared by a Stille coupling, and the supramolecular behavior in solution was studied. In a good solvent (THF), the polymers are present as unordered, highly conjugated, rigid-rod-like strands. Upon addition of a nonsolvent (hexane) or in toluene, the polymer strands adopt a helical conformation in contrast to previously reported alkyl-substituted PDTPs, which aggregate by decreasing the solvent quality. The folding and unfolding process was investigated by probing the UV−vis and CD intensities at different wavelengths and temperatures. On the basis of these experiments, it could be concluded that the helical folding and unfolding is a single-step process. The PDTP could also be oxidized and rereduced, and thus, in principle, a molecular solenoid can be obtained.