Dual Functionality of Schiff Base: Sensing of Metal Ions and Broad-Spectrum Antibacterial Effects

In this study, a novel Schiff base sensor (SBS) was synthesized and characterized by fluorescence and ¹H NMR spectroscopy. The sensing ability of the Schiff base was evaluated toward Hg²⁺, Fe³⁺, K⁺, Mg²⁺, Ni²⁺, Li⁺, Ca²⁺, Cu²⁺, Cr³⁺, Cd²⁺, Co²⁺, Na⁺, Ag⁺, and Zn²⁺. Among the tested metal ions, SBS demonstrating high selectivity and sensitivity toward Ag⁺ and Fe³⁺ ions, with notable changes in fluorescence spectra upon binding. These changes were due to formation of complexes SBS-Ag⁺ and SBS-Fe³⁺. The limit of detection (LOD) was calculated to be 0.0028 ppm (0.026 µM), for Ag⁺ and 0.0016 ppm (0.028 µM) for Fe³⁺. Furthermore, the Schiff base and its metal complexes SBS-Ag⁺ and SBS-Fe³⁺ were tested for antibacterial activity against various bacterial strains. The results revealed significant enhancement in antibacterial efficacy upon coordination with Ag⁺ and Fe³⁺, indicating that the Schiff base-metal complexes exhibit superior activity compared to the free ligand. The improved biological activity is attributed to the metal coordination, which increases the lipophilicity of the complexes, facilitating their penetration into bacterial cell membranes.