Dithiabenzisapphyrin:  A Core-Modified Sapphyrin Bearing Exocyclic Double Bonds at the meso-Positions

A dithia analogue of meso-alkylidenyl sapphyrin, a class of compounds that was hitherto unknown, was prepared via the condensation of a 1,3-phenylenebispyrrole with a bithiophene diol. The resulting system was found to be stable and highly nonplanar. It was also characterized by a partially conjugated electronic structure. As such, this system helps to underscore the emerging impression that conjugation and aromaticity effects in expanded porphyrins may be more protean than previously appreciated. Specifically, this work serves to demonstrate that even nonplanar structures can show partial conjugation effects.