A molecular switch-type receptor recognizes aqueous acetate by facilitating proton transfer through hydrogen bonding

Aqueous anion recognition using artificial receptors is of great interest but full of challenges. Typically, anion-selective receptors are designed by selecting scaffolds that have either hydrogen bonding sites or positively charged moieties. Herein, we constructed an acetate-responsive chromogenic molecular switch with a phenolphthalein backbone and achieved the visual recognition of acetate in pure water. UV–Vis and 1H NMR titration data reveal that the molecular switch receptor has good selectivity and binding towards acetate. Mechanistic studies have shown that this molecular switch-type anion receptor recognizes acetate through hydrogen bonding to facilitate proton transfer. Our findings are expected to pave the way for a new class of aqueous anion receptors and the development of new molecular recognition mechanisms.