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. © 2012 Elsevier B.V. All rights reserved.