Three-Stage Aromaticity Switching in Boron(III) and Phosphorus(V) N-Fused p-Benziporphyrin.

Insertion of PCl3 or PhBCl2 into 5,10,15,20-tetraaryl-p-benziporphyrin prompted an intramolecular fusion affording anti-aromatic phosphorus(V) and non-aromatic boron(III) complexes of two N-fused dihydro-p-benziporphyrin isomers. These macrocycles are classified as carbatriphyrin due to the common [CNN] coordination. A sequence of direct transformations, triggered by protonation or two-electron redox processes, afforded a set of three mutually convertible N-fused p-benziporphyrinoids, with distinct anti-aromatic, non-aromatic, and aromatic spectroscopic features.