Fluorescent chemosensor based on bispicolylamine for selective detection of magnesium ions

In this study, an assay to quantify the presence of magnesium ions with a chemosensor of bispicolylamine covalently attached to coumarin as a fluorephore was developed using a ratiometric fluorescence enhancement approach. Upon treatment with magnesium ions, the fluorescence wavelength of the chemosensor at 367 nm was shifted to 413 nm and the intensity was also enhanced. The formation of a 1:2 complex between the chemosensor and magnesium ions was confirmed based on the spectral changes of UV-vis, fluorescence and NMR as well as Job's plot. An appreciable enhancement in the luminescence intensity for the emission band at 413 nm was evident when magnesium ions were added progressively. The maximum wavelength and intensity of the emission of the complex with Mg²⁺ were discriminated from those of other metal ions, such as Ca²⁺ and Zn²⁺.