<i>Meso</i> -Modified Porphyrinoids: Stimuli-Driven Conformational Plasticity, Modulation of π-Conjugation, and Bis-Rh(I) Complexation

Topology and the extent of π-electron delocalization govern the (anti)aromatic behavior in macrocycles. We report <i>meso</i>-carbon-amended porphyrinoids with <i>ortho</i>-benzannulation at the periphery for rigidity and vinylogous linkages for flexibility. This design enables stimuli-responsive conformational plasticity and tunable (anti)aromaticity, manifesting as moderate Hückel antiaromaticity in freebases, weak Möbius aromaticity upon protonation, and nonaromaticity through bis-Rh(I) complexation, resulting in foldameric structures with η² coordination and panchromatic absorption. Thus, this design reveals topology-property relationships in π-conjugated macrocycles.