Dual-functional Schiff base with pyridine moiety: antibacterial activity and colorimetric detection of Cu²⁺ ions

Schiff bases are well-known for their structural versatility, ease of synthesis, and excellent metal-binding capabilities, making them promising candidates for dual-functional applications such as sensing and antimicrobial evaluation. In this study, we report the synthesis of a novel Schiff base (<b>SBPY-1</b>) incorporating a pyridine moiety, designed as a colorimetric probe for the selective and sensitive detection of Cu²⁺ ions. The probe demonstrated a distinct and rapid colour change from colourless to yellow upon interaction with Cu²⁺, enabling naked-eye detection without the need for sophisticated instrumentation. The sensor exhibited excellent selectivity for Cu²⁺ over a range of competing metal ions and displayed remarkable sensitivity, with a detection limit as low as 0.011 ppm (0.17 µM). Its practical utility was validated through successful detection of Cu²⁺ in various real water samples, including lake, river, pond, well, wastewater, and drinking water as well as in blood serum, achieving high recovery rates ranging from 90.0 ± 0.58% to 104.0 ± 0.65%. In addition to its sensing capabilities, the Schiff base (<b>SBPY-1</b>) and its Cu(II) complex (<b>SBPY-1-Cu(II)</b>) were evaluated for their antibacterial activity against a broad spectrum of Gram-positive and Gram-negative bacteria. While the free ligand exhibited moderate antibacterial effects, complexation with Cu(II) significantly enhanced the antimicrobial performance. These findings highlight the potential of this dual-functional Schiff base for both environmental monitoring of Cu²⁺ ions and as a lead compound for the development of metal-based antimicrobial agents.