Synthesis and properties of a nanographene-embedded conjugated macrocyclic nanoring via the Scholl reaction

Direct π-extension by the Scholl reaction for solution-based growth of armchair edges in curved macrocyclic hydrocarbon nanostructures is a great challenge. To date, several attempts at direct π-extension of small highly strained macrocycles have failed. Herein, we report a fixed two-bond approach for direct functionalization of small strained macrocyclic nanorings. The reaction occurs selectively to produce large π-extended molecular crowns with high yields. The design of these precursors features two peripheral C–C bonds that are readily incorporated into the extended aromatic moiety to overcome strain-induced side reactions, such as 1,2-phenyl shift. The crown-shaped macrocycle 10 showed a significant redshift (∼100 nm for absorption) compared with its precursor. This synthesis strategy could pave the way towards the π-extension of strained conjugated macrocycles and their potential applications in electron-transport devices.