Highly Strained, Fully π‐Conjugated Porphyrin Cyclophanes: Template‐free Synthesis and Global Aromaticity

Abstract

Porphyrin‐based nanohoops, nanorings, and cages with fully π‐conjugated structures are highly sought after, but their synthesis remains challenging. Herein, we report the template‐free synthesis of a highly strained, bithiophene‐bridged porphyrin cyclophane (1) from a porphyrin quinone via a stereoselective nucleophilic addition followed by intermolecular Yamamoto coupling strategy. X‐ray crystallographic analyses of 1 and its dication 12+ reveal significantly distorted cyclophane‐like geometries, with calculated strain energies of 51.2 and 80.7 kcal/mol, respectively. While the neutral compound 1 exhibits localized aromaticity, the dication 12+ is globally aromatic, with the porphyrin unit displaying weak antiaromaticity. Additionally, the dication 12+ undergoes nucleophilic addition with chloride, relieving strain. This work presents a novel synthetic strategy for highly strained, fully π‐conjugated systems with intriguing electronic properties and chemical reactivity.