Reversible Oxidation of a Nonathia[42]Nonaphyrin(1.1.0.1.1.0.1.1.0) to a 40π Dication Diradicaloid

A one-pot condensation of bithiophene with thiophene diol under acidic conditions yields 28π, 42π, and 56π expanded porphyrinoids. X-ray crystallographic studies revealed a planar topology for both 28π and 42π macrocycles. Spectroscopic and quantum chemical calculations reveal weak ring current effects, while they undergo reversible two-electron ring oxidation as confirmed by electrochemical studies. Spectroscopic and quantum chemical calculations support a diradicaloid character for the 40π dicationic species.