Zinc selective chemosensors based on the flexible dipicolylamine and quinoline

Abstract Zinc sensor molecules containing quinoline have been synthesized, which show fluorescence in the presence of Zn 2+ . The nitrogen in quinoline is critical to fluorescence and fluorescence enhancement is promoted by deprotonating the sensor’s amide. One of the sensors is highly selective for Zn 2+ over Cd 2+ and other cations such as Hg 2+ , Fe 2+ , Mn 2+ and Ca 2+ . This selectivity can be attributed to the increased absorption of the sensor in the presence of Zn 2+ and the strong binding of Zn 2+ . Structural studies, including X-ray and NMR, show the ability of dipicolylamine (DPA) to bind in facial and meridional manners to Zn 2+ . Crystal structures of different compounds show Zn 2+ coordinating to three, four, and five nitrogens from the compounds. They also indicate that the selectivity of DPA containing compounds towards Zn 2+ may originate from Zn 2+ being stable in different coordination environments.