Syntheses of Anthracene‐Centered Large PAH Diimides and Conjugated Polymers

Polycyclic aromatic hydrocarbon (PAH) structures with suitable electron‐withdrawing groups are useful building blocks for developing optical and electron‐transporting materials. Here, we report the application of a double benzannulation process to the syntheses of PAH diimides with enlarged π‐frameworks featuring a central anthracene moiety. The preparations are realized by copper‐catalyzed [4+2] cycloaddition of ethynyl‐substituted aromatic dicarboximide to 2,5‐bis(phenylethynyl)terephthalaldehyde, followed by intramolecular photocyclization or direct arylation via Heck cross coupling. A central symmetric benzo[1,2‐k:4,5‐k′]‐bis(fluoranthene)‐3,4,12,13‐tetracarboxyl diimide (BFDI) is acquired, with the single crystal structure revealing its completely planar polycyclic skeleton. Such a shape‐persistent PAH expectedly exhibits a tendency to stack face‐to‐face and forms J‐aggregates. Moreover, BFDI can be difunctionalized site‐selectively at the reactive 9 and 10 positions of the anthracene unit and then applied to prepare conjugated polymers. When coupled with 1,4‐diketopyrrolo[3,4‐c]‐pyrrole (DPP) via thiophene and dithiophene linkers, two polymers with significantly broadened absorption bands extended to the near‐infrared regime are obtained, evidencing the effective π‐conjugative extension ability of BFDI unit. A benzannulation reaction followed by intramolecular arylation has been applied to the synthesis of a PAH diimide (BFDI) featuring a central anthracene moiety. When BFDI is coupled with 1,4‐diketopyrrolo[3,4‐c]‐pyrrole (DPP) via thiophene and dithiophene linkers, two polymers with significantly red‐shifted, broad absorptions are prepared, evidencing the effective π‐conjugative extension ability of BFDI and charge‐transfer characteristic of the polymer backbones.