Synthesis, Sensing Performance and DFT Studies of a Novel Coumarin-based Schiff Base As a Turn-on Fluorescence Probe...

The design and development of novel efficient fluorescent chemical sensors for the selective detection of ions is currently of significant importance in supramolecular chemistry. Since zinc is a ubiquitous, indispensable and the second most abundant metal ion in the human body, developing chemosensors that can accurately discriminate between Zn²⁺ and Cd²⁺ ions has been a challenge due to their similar properties as they are in the same group of the periodic table. Therefore, a technique to trace and visualize free zinc ions is demanded. In this study, an innovative coumarin-based Schiff base (L) was synthesized and characterized by ¹H NMR, ¹³C NMR and mass spectroscopy. A novel "Turn On" fluorescence chemosensor platform was developed for trace amounts of Zn²⁺ ions. The fluorescence Job's plot measurement was used to determine the complexation ratio between the probe and Zn²⁺ ion, which showed a maximum point indicating the formation of a ML₂ adduct. Additionally, the geometrical parameters calculated using DFT and TD-DFT calculations were in close agreement with the experimentally observed values.