Versatile helicene building blocks for organic electronics

Semiconducting organic molecules are used extensively in the fabrication of next-generation electronics, which have increased flexibility, processability, and versatility. The use of imide-based aromatic molecules in particular is widespread in n-type electronics, and modifications to naphthalene-diimide and rylene-diimide structures have advanced the properties and applications of these molecules. Here we report the use of the perylene-diimide-inspired helicene N[5]HDI as a new building block of electronic materials. The gram-scale accessibility and selective bromination at key core-extending positions make N[5]HDI an appealing monomeric unit for incorporation into larger molecules with electronically-coupled subcomponents. Specifically, we demonstrate that N[5]HDI undergoes several different palladium-catalyzed cross-coupling reactions (Suzuki, Sonogashira, Stille, and Heck) in near-quantitative yields. The resultant π-extended derivatives of N[5]HDI electronically couple the helicene core to the terminal aryl, alkenyl, or alkynyl units despite the overall coiled shape of these molecules. Copolymers of N[5]HDI show continued extension of electronic communication and a further decreased HOMO-LUMO gap with increased chain length. N[5]HDI exhibits strong potential as a helical building block of electronically-coupled materials and for future explorations in organic electronic applications.