Fluorescent chemosensors have made significant advances in the development of low-cost, rapid-responding probes to selectively recognize analytes, such as heavy metals, anions, and toxic gases. In contrast to the well-developed cation chemosensors, anion chemosensors development has proved challenging because of the variation of size, geometry, and strong solvation of the species.¹ Particularly, fluorescent chemosensors for sensing halide anions have been an important research area in biological and environmental systems. However, it has been challenging to distinguish between halides due to their weak selective response. Current metal complex-based chemosensors have been limited to the use of d-block transition metals, including rare earth metals. Few known studies have been reported using p-block metals. We have recently developed new tin(IV) halide complexes (SnQ₂X₂, Q= hydroxyquinoline derivatives, X=halogens), demonstrating that the nature of the halide bound to the tin metal center alters photophysical properties, such as carrier lifetime, chemical stability, quantum efficiency, and aggregation-induced emission.^2,3 This leads to exploration of new applications for fluorescent chemosensors due to their distinct, Sn-halogen bonding-based, luminescence changes (enhancement or quenching). Herein, we report the first multi-halide sensors based on Sn(IV) halide complexes that exhibit “turn-on” or “turn-off” behavior depending on halide ions(analytes). The photophysical properties of the Sn(IV) halide complexes will be discussed for potential fluorescent chemosensors for halide recognition.

(1) Beer, P. D.; Gale, P. A. Anion Recognition and Sensing: The State of the Art and Future Perspectives. Angew. Chemie Int. Ed. 2001, 40 (3), 486–516.
(2) Ngo, K.; Averkiev, B.; Reeves, G. T.; Wu, A.; Ki, D. W. Tin(IV) Halide Complexes with 5,7-Dimethyl-8-Quinolinol: Structures, Optical and Thermal Properties. J. Coord. Chem. 2022, 75 (5–6), 796–807.
(3) Ki, W.; Ngo, K.; Ghosh, P.; Averkiev, B.; Reeves, G. T.; Ailes, I.; Pemberton, B. C.; Zhu, K.; Li, J. Blue-Shifted Aggregation-Induced Enhancement of a Sn( Iv ) Fluoride Complex: The Role of Fluorine in Luminescence Enhancement . Chem. Commun. 2020, 56 (67), 9648–9650.

Wooseok Ki

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