Synthesis and optical behaviors of novel triazole fluorescent probes involving solvatochromic behavior, metal ions detection and their antibacterial activity

In this study, two novel fluorescent probes incorporating a triazole moiety, namely (E)-5-((4 H-1,2,4-triazol-3-yl)diazenyl)quinolin-8-ol (probe 1) and (E)-3-((4 H-1,2,4-triazol-3-yl)diazenyl)-4-hydroxybenzoic acid (probe 2), were synthesized and structurally characterized. Their photophysical properties were evaluated in solvents of varying polarity, showing pronounced solvatochromic shifts and enhanced molecular polarization upon excitation. The chemosensory behavior of the probes toward a series of metal ions, including Na+, Mg2+, K+, Cr3+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Ba2+, and Hg2+, was also examined. The probes exhibited high selectivity and sensitivity for Co2+ ions via fluorescence turn-on/off mechanisms, with binding constant analysis confirming the strongest affinity for Co2+. The limits of detection (LOD) for Co2+ were determined to be 0.58 µM for probe (1) and 0.06 µM for probe (2), both values significantly lower than the maximum permissible limits set by the US Environmental Protection Agency (EPA) and the World Health Organization (WHO) for drinking water. Furthermore, both probes demonstrated promising antibacterial activity against clinically relevant strains, including multidrug-resistant Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae, indicating their potential for further development as antimicrobial agents.