Two-electron Oxidation of a Twisted Non Anti-aromatic 40π Expanded Isophlorin

Abstract

Expanded isophlorins are typical examples for stable anti-aromatic systems. Paratropic ring current effects are observed in their NMR spectra mainly due to their planar conformation. Herein we report the synthesis of the first twisted 40 π expanded isophlorin and also its two-electron oxidation to a 38 π dication. It sustains the twisted conformation for the 4n π and (4n + 2) π electrons. Due to the non-planar conformation, they do not display ring current effects in their respective1H NMR spectrum. NICS calculations reveal the non-(anti)aromatic features for the neutral 40 π and the 38 π dication species.