An ionic binaphthyl-bridged imidazole dimer for fast visible-light-driven negative photochromism in aqueous media

We report a binaphthyl-bridged imidazole dimer bearing alkylpyridinium groups that exhibit fast and visible-light-induced negative photochromism even in aqueous media. The introduction of ionic groups not only enhances water solubility but also induces charge-transfer absorption, enabling efficient blue-light activation.