A Stable Antiaromatic 5,20-Dibenzoyl [28]Hexaphyrin(1.1.1.1.1.1): Core Au Metalation and Subsequent Peripheral B 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 Au afforded rectangular and aromatic [26]hexaphyrin bis-Au complexes, the major isomer of which was reduced with NaBH to give its antiaromatic 28π bis-Au complex. This complex allowed facile peripheral metalation with B owing to the peripheral benzoyl substituents.