A Stable Antiaromatic 5,20-Dibenzoyl [28]Hexaphyrin(1.1.1.1.1.1): Core AuIII Metalation and Subsequent Peripheral BIII Metalation.

5,20-Dibenzoyl [28]hexaphyrin(1.1.1.1.1.1) was synthesized as the first hexaphyrin bearing meso-aroyl substituents. The meso-dibenzoyl substituents are hydrogen-bonded with the pyrrolic protons to stabilize an antiaromatic dumbbell conformer. Core metalation of this hexaphyrin with AuIII afforded rectangular and aromatic [26]hexaphyrin bis-AuIII complexes, the major isomer of which was reduced with NaBH4 to give its antiaromatic 28π bis-AuIII complex. This complex allowed facile peripheral metalation with BIII owing to the peripheral benzoyl substituents.