Aggregation induced emission active Schiff base compounds: from fundamentals to applications

The design of fluorescent turn-on receptors capable of selectively and sensitively detecting specific ions has become a major focus of current research. This review summarizes recent developments in fluorescent Schiff base–derived chemosensors for the selective and sensitive detection of biologically and environmentally important metal ions and anions. Transition metal ions play essential roles in numerous physiological and ecological processes, making their precise monitoring critically important. Schiff base systems have emerged as promising sensing platforms due to their facile synthesis, high thermal and photostability, and characteristic optical behavior, including weak baseline fluorescence and significant emission enhancement upon metal coordination through CHEF, CHEQ, FRET, and ICT mechanisms. The incorporation of fluorescent chromophores further strengthens their signaling capability, enabling effective cellular imaging with low cytotoxicity and good reversibility. Particular emphasis is placed on aggregation-induced emission (AIE), which offers enhanced stability, tunability, and aggregation-enhanced luminogenic properties, thereby expanding potential applications in environmental sensing and functional material design. Despite notable progress, limitations such as insufficient selectivity for hazardous metal removal remain challenges in water-quality applications. Overall, advancements in Schiff base–based fluorescent probes continue to drive innovation in metal-ion sensing, environmental monitoring, and biomedical diagnostics.