Peripheral fabrications of a bis-gold(III) complex of [26]hexaphyrin(1.1.1.1.1.1) and aromatic versus antiaromatic effect on two-photon absorption cross section

Peripheral modifications of bis-gold(III) [26]hexaphyrin(1.1.1.1.1.1) have been explored via perbromination and subsequent Pd-catalyzed cross-coupling reactions. beta-Phenylethynylated [26]hexaphyrin complex shows the large two-photon absorption (TPA) value due to its extended pi-conjugation. Aromatic-to-antiaromatic switches through two-electron reduction from [26]hexaphyrins to [28] hexaphyrins cause a sharp drop in TPA value, which has emerged as a new quantitative measure of aromaticity versus antiaromaticity.