A Stable Radical Species from Facile Oxygenation of meso-Free 5,10,20,25-Tetrakis(pentafluorophenyl)-Substituted [26]Hexaphyrin(1.1.1.1.1.)

摘要

In recent years, the potential of expanded porphyrins (conjugated pyrrolic macrocycles larger than porphyrins) has been increasingly recognized owing to their unique chemical, optical, and electrochemical properties as well as rich coordination chemistry. Besides their earlier uses as scaffolds for anion binding and their unique metal-metal interactions, recent interesting findings have been reported, including 1) a smooth metathesis-type splitting reaction of the bis(Cu~(II)) complex of [36]octaphyrin(1.1.1. 1.1.1.1.1) into two molecules of Cu~(II) porphyrin,2) transannular annulation reactions between two ethynyl groups or between ethynyl and phenyl groups of meso-substituted hexaphyrins to provide unique rearranged products, and 3) the facile formation of stable antiaromatic or twisted Mobius aromatic systems. These results indicate that expanded porphyrins can fulfill roles that are not only difficult for porphyrins but are novel and important in their own right. Herein, we report another unexpected function of expanded porphyrins, namely of [26]hexaphyrin, to stabilize a radical species to the extent that it can be manipulated as a normal closed-shell organic molecule in the presence of air and moisture. To the best of our knowledge, this finding is without precedent in the chemistry of porphyrins.