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. It′s as simple as 1, 2, 3! p‐Benziporphyrin undergoes deep structural modifications induced by the coordination of boron(III) or phosphorus(V), forming N‐fused p‐benziporphyrinoids which imprint a carbatriphyrin(3.1.1) motif. A distinctive structural frame of contracted carbaporphyrinoid creates a three‐level aromaticity switching system.