Quadruply Twisted Hückel‐Aromatic Dodecaphyrin

Molecular topology of π‐conjugated circuits becomes increasingly important in the chemistry of aromatic and antiaromatic compounds. meso‐Pentafluorophenyl‐substituted 5,35‐(1,4‐phenylene)bridged [56]dodecaphyrin was synthesized by condensation of 1,4‐phenylene‐bridged dicarbinol dimer and 5,10,15‐tris‐(pentafluorophenyl)tetrapyrrane followed by oxidation with DDQ and was oxidized to its [54]‐ and [52]congeners in a stepwise manner. Metalation of the [52]dodecaphyrin with Pd 2 (dba) 3 gave two bis‐Pd II complexes that are isomers of metalation sites: anti and syn with regard to the 1,4‐phenylene bridge. The anti‐isomer was easily oxidized to its N‐fused form, a quadruply twisted non‐aromatic or weakly aromatic macrocycle. On the other hand, the syn‐isomer was revealed to be the first example of Hückel aromatic molecule with a quadruply twisted structure.