Facile Redox-Induced Aromatic-Antiaromatic Interconversion of a β-Tetracyano-21,23-Dithiaporphyrin under Ambient Conditions.

Facile redox-induced aromatic-antiaromatic interconversions were accomplished by using β-tetracyano-21,23-dithiaporphyrin (CN S Por). Introduced cyano groups not only increased the reduction potential of the porphyrin core but also stabilized the antiaromatic isophlorin (CN S Iph) by π conjugation. The reduction of CN S Por with hydrazine in polar solvents quantitatively affords CN S Iph, even under ambient conditions. CN S Iph retains a nearly planar conformation and exhibits considerable antiaromaticity. Aerobic oxidation of CN S Iph to CN S Por occurs in nonpolar solvents. This study was conducted to contribute to the understanding of the structure-antiaromaticity relationship.