Polymerization of Porphyrins by Indenyl Coupling

Abstract

Porphyrin polymers merge the photophysical, electrochemical, sensory and catalytic properties of porphyrins with the processability and robustness of polymeric materials, offering versatile and synergetic platforms for optoelectronics and catalysis. Here we report an on-surface strategy for the atomically precise polymerization of porphyrins via regioselective indenyl coupling. Deposition of an indenyl-functionalized porphyrin on Au(111) and sequential annealing drives a stepwise transformation: cyclodehydrogenation at 100 °C planarizes the precursor into π-extended porphyrins, while annealing above 125 °C triggers carbon–carbon homocoupling through five-membered moieties, forming short oligomers. Heating to 150 °C promotes chain growth into one-dimensional polymers with a 1.1 eV bandgap and extended π delocalization, alongside a minor fraction of cyclic trimers featuring a 1.1 eV HOMO–LUMO gap with both local and global aromaticity. The methodology also proceeds for Co-metallated precursors, confirming that indenyl coupling is also compatible for metalloporphyrins, establishing a general route to design π-extended porphyrin polymers.

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