Topoisomers and aromaticity of a redox active 50π core-modified isophlorinoid

Abstract

A 50π decathiophene expanded isophlorin adopts a unique [6+4] conformation and a near-planar conformation depending on the solvent of crystallization and undergoes a reversible two electron oxidation to yield the largest planar antiaromatic dication bearing 48π–electrons. Cyclic voltammetry studies revealed the redox active nature of this macrocycle with multiple oxidation and reduction potentials. Spectro-electrochemical measurements confirmed a facile reversible two-electron oxidation and the unstable radical cation intermediate in these systems. Quantum chemical calculations that were employed to estimate NICS(0) values revealed a weak diatropic ring current for the 50π macrocycle and an intense paratropic ring current for the 48π dicationic species.