A Modular Synthesis of Planar, Redox-Stable Hückel Anti-Aromatic [36]Nonaphyrin (1.0.0.1.0.0.1.0.0) with Only Three meso-Bridges

A rigid dithienopyrrole (DTP) subunit was functionalized by taking advantage of the fused core, which upon Lewis acid-catalyzed self-condensation afforded two structurally distinct expanded porphyrinoids, namely [36]nonaphyrin (S₆N₃) and [48]dodecaphyrin (S₈N₄). The single crystal X-ray structure of S₆N₃ revealed a perfectly planar conformation. Various spectroscopic and DFT analyses unambiguously confirmed the strong anti-aromatic feature of S₆N₃, and the large expanded congener S₈N₄ displayed a nonplanar conformation with weak anti-aromaticity.