The reaction of hexaphyrin with triethylamine in the presence of BF3 OEt2 and O2 furnished a diastereomeric mixture of a diethylamine-bearing hexaphyrin as a rare example of a Möbius aromatic metal-free expanded porphyrin. The Möbius aromaticity of these molecules is large, as indicated by their large diatropic ring currents, which are even preserved at 100 C, owing to their internally multiply bridged robust structure with a smooth conjugation network. These molecules were reduced with NaBH4 to give an antiaromatic hexaphyrin, and were oxidized with MnO2 to give aromatic hexaphyrins, both through a Möbius-to-Hückel topology switch induced by a C-N bond cleavage.
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