62: Rational design of metal-complex chemosensors for selective detection of environmental anions and PFAS

Abstract: Environmentally persistent anions such as fluoride and per- and polyfluoroalkyl substances (PFAS) pose significant risks to human health and ecosystems, necessitating rapid, selective, and cost-effective sensing platforms. Metal complexes are particularly attractive sensing scaffolds because their tunable coordination environments and electronic structures enable precise control of analyte binding and photophysical response. Here we report a rational design strategy for fluorescent chemosensors that exploits coordination-controlled photophysics within metal–ligand architectures to achieve selective recognition of diverse anionic targets. Within this framework, hydroxyquinoline-based metal complexes were systematically engineered to modulate ligand electronics, coordination geometry, and exchangeable binding sites, enabling predictable tuning of optical properties. Tin(IV) complexes function as turn-on fluorescent probes for fluoride through halide-exchange-induced electronic reorganization, exhibiting high selectivity, 1:2 binding stoichiometry, and a detection limit of 1.0 × 10-7 M. Structural and computational analyses indicate that fluorination stabilizes the complex and increases dipole moment, thereby enhancing emission intensity and sensing sensitivity. Extending this design principle, a neutral indium (III) analogue displaying aggregation-induced emission enables selective detection of PFAS (PFOA and PFHpA) via analyte-induced luminescence quenching and blue-shifted emission arising from preferential ground-state stabilization. These probes respond rapidly (~1 min), exhibit defined binding stoichiometry, and show detection limits near 5 × 10-4 M. Collectively, these findings demonstrate that metal-halide complexes provide a generalizable platform for tuning photophysical responses through anion exchange and for developing next-generation fluorescent chemosensors for environmental monitoring and real-time chemical detection.