Reversible Ring Oxidation of 48π Planar Nonaphyrins to Open Shell 46π Dications

We report the synthesis and characterization of 48π nonaphyrins, a novel class of planar expanded porphyrinoids exhibiting distinct electronic properties compared to their 32π congeners. Single-crystal X-ray diffraction studies revealed heterocycle dependent structural topology for these macrocycles. All the isolated nonaphyrins display weak paratropic ring current effects and undergo reversible two-electron ring oxidation to yield the respective 46π dicationic diradicaloid species. The formation of oxidized diradicaloid species was confirmed by ESR spectroscopy, spectro-electrochemical measurements and further supported by quantum chemical calculations.