Fluorescence switch for silver ion and pyridine sensing

A double-arm anthracene, 9,10-bis(1′-picolylbenzimidazolium-ethoxyl)anthracene hexafluorophosphate (L), was synthesized and characterized. Fluorescence switch of L under the induction of Ag⁺ and pyridine (Py) was studied. Compound L displayed a strong fluorescence emission at 390–550 nm. Upon adding Ag⁺to the solution of L, the fluorescence intensity of L decreased remarkably due to the formation of LAg⁺. Then, as pyridine was gradually added, the fluorescence intensity of LAg⁺gradually increased until the fluorescence intensity approached that of L, where LAg⁺Py was formed. Throughout the entire process, the fluorescence of L showed a change from "on" to "off" and then back to "on" under the induction of Ag⁺ and pyridine.