Meso-Aryl [20]p Homoporphyrin: The Simplest Expanded Porphyrin with the Smallest Mçbius Topology

Abstract

An unstable conjugated homoporphyrin was successfully stabilized by introducing meso-aryl substitutents. It was evident from the moderate diatropic ring current found by NMR analysis that the newly formed 20p conjugated free base and its protonated form exhibited Mçbius aromatic character. Furthermore, complexation as a ligand with an RhI ion afforded a unique binding mode and retained the Mçbius aromaticity. Overall, these compounds are the smallest Mçbius aromatic molecules, as confirmed by spectral and crystalstructure analysis and supported by theoretical studies.