A Negatively Curved Porphyrin [10]Circulene

A curved five-porphyrin circulene has been synthesized through oxidative fusion of a cyclic precursor, prepared by Yamamoto coupling. The saddle-shaped geometry of this molecule was confirmed by single-crystal X-ray diffraction. In solution, it undergoes a rapid saddle-to-saddle inversion, even at 200 K, resulting in a simple 1 H NMR spectrum. Despite its pronounced negative curvature (Gauss curvature: –0.30 Å –2 ), it exhibits efficient electronic delocalization, with an electrochemical band gap of 0.88 eV and near-infrared absorption (λ max 1200 nm). It has a high affinity for C 60 and C 70 , in toluene at 298 K. There is no significant bond length alternation around the central 10-membered ring, and computational studies reveal a substantial diatropic current around this ring, establishing the porphyrin circulene as a globally aromatic curved nanographene.