A real-time fluorescent sensor specific to Mg2+: crystallographic evidence, DFT calculation and its use for quantitative determination of magnesium in drinking water

Abstract

An “off-the-shelf” fluorescence “turn-on” Mg²⁺ chemosensor 3,5-dichlorosalicylaldehyde (BCSA) was rationally designed and developed. This proposed sensor works based on Mg²⁺-induced formation of the 2 : 1 BCSA–Mg²⁺ complex. The coordination of BCSA to Mg²⁺ increases its structural rigidity generating a chelation-enhanced fluorescence (CHEF) effect which was confirmed by single crystal XRD studies of the BCSA–Mg²⁺ complex and TD/DFT calculations. This sensor exhibits high sensitivity and selectivity for the quantitative monitoring of Mg²⁺ with a wide detection range (0–40 μM), a low detection limit (2.89 × 10⁻⁷ mol L⁻¹) and a short response time (<0.5 s). It can also resist the interference from the other co-existing metal ions, especially Ca²⁺. Consequently, this fluorescent sensor can be utilized to monitor Mg²⁺ in real time within actual samples from drinking water.