DESIGN, SYNTHESIS AND CHARACTERIZATION OF FLUORESCENT CHEMOSENSORS FOR SELECTIVE RECOGNITION OF METAL CATIONS IN SOLUTION

This project involves the design, synthesis, coordination, and photochemical analysis of fluorescent ligands (L1-L8). Each ligand, except L6, has one or two fluorophores linked to a polyamine chain, enabling it to detect specific metal ions in solution by altering its fluorescence. Two fluorophores, HNBO (F1) and HBO (F2), were used, with HNBO-based ligands L1 and L2 showing ESIPT only in ACN. These ligands switch fluorescence "on" in the presence of selected metal ions, displaying different behaviors in solvents like DMSO and ACN, with selectivity for Mg²⁺, Zn²⁺, and Cd²⁺. L1 and L2 also perform well as metal ion detectors on paper (strip-test), with L1 selective for Zn²⁺ and L2 for both Zn²⁺ and Cd²⁺. L3, meanwhile, selectively binds to Mg²⁺ and shows promise for solid-state optodes in water sample testing due to its stability, sensitivity, and ease of use. L6, which lacks a polyamine chain, has high selectivity for zinc and has been tested for solar cell applications. The project further explores ligands for rare earth (RE) ions, developing L4 and L5 with increased donor atoms and L7-L8 for specific RE ion signaling. L8 was optimized to detect Ce(III) with high selectivity and sensitivity (LOD of 0.1 ppm), offering a solution and strip-test method suitable for polluted water analysis, with minimal interference from other ions.