Expanding the porphyrin π-system by fusion with anthracene

Synthesis of beta,meso,beta-anthracene triply fused and beta,meso-anthracene doubly fused porphyrins has been achieved via oxidative intramolecular ring closure of meso-(9-anthryl)porphyrins and meso-(1-anthryl)porphyrins, respectively. Fusion was only possible when the anthracene carried electron-donating alkoxy substituents. The fused porphyrins exhibit strongly red-shifted UV-vis absorption spectra and reduced electrochemical HOMO-LUMO gaps (relative to the unfused tetraaryl porphyrin precursor).