A Möbius antiaromatic complex as a kinetically controlled product in phosphorus insertion to a [32]heptaphyrin

Singly twisted Möbius antiaromatic [34]heptaphyrin 8 and doubly twisted Hückel aromatic [34]heptaphyrin 9 were formed in the phosphorus insertion reaction to [32]heptaphyrin 7. The Möbius antiaromatic character of 8 has been confirmed on the basis of its X-ray structure, a weak paratropic ring current, ill-defined absorption characteristics, fast excited-state decay, and a relatively small TPA crosssection. In aliphatic nitrile solutions, complex 8 underwent the quantitative thermal migration of the P=O moiety to produce more stable 9 with the concurrent molecular topology switch, thus indicating the complex 8 to be a rare case of a kinetically controlled Möbius antiaromatic species.