Post-functionalization of alternating π-conjugated copolymers containing fluorene moieties via anodic chlorination using AlCl3

Abstract

Fluorene (Fl) derivatives are representative emitting motifs; thus, they are often installed into alternating π-conjugated copolymers (P(Fl-Ar)) as soluble polymeric emitters. Many researchers have focused on modifying the combined arylene units in P(Fl-Ar) derivatives to tune their optoelectronic properties; however, P(Fl-Ar) derivatives that contain fluorene units with functional groups at their sp2 carbons remain limited. Here, we synthesize P(Fl-Ar) derivatives comprising sp2-chlorinated fluorene units via anodic chlorination using aluminum chloride (AlCl3). The introduced chlorine atoms affect the optoelectronic properties of the pristine P(Fl-Ar) derivatives. Compared with the precursor P(Fl-Ar) derivatives, chlorinated P(Fl-Ar) derivatives exhibit longer maximum emission wavelengths. Alternating π-conjugated copolymers containing 9,9-dialkylfluorene (Fl) units have been widely studied, but there are few of these copolymers with sp2-carbon functionalized Fl units. In this study, we expand this limitation by performing the anodic chlorination of alternating π-conjugated copolymers, which are composed of Fl and another arylene (Ar) (P(Fl-Ar)s), using an acetonitrile solution that contains aluminum chloride as an electrolyte. The sp2-carbon at the fluorene ring was successfully chlorinated by anodic chlorination. P(Fl-Ar)s containing sp2-chlorinated fluorene units has different emission properties from the original P(Fl-Ar)s.