1‑Pyrenyl- and 3‑Perylenyl-antimony(V) Derivatives for the Fluorescence Turn-On Sensing of Fluoride Ions in Water at Sub-ppm Concentrations

In the context of our work on main
group-based anion sensors, we
have synthesized the bromide salts of a series of tetraarylstibonium
cations of general formula [ArSbPh3]+ with Ar
= 9-phenanthryl ([1]+), 1-pyrenyl- ([2]+), and 3-perylenyl ([3]+). While [1]+ is not stable in water, we
found that [2]+ and [3]+ can be used as sensors for the sub-ppm detection of fluoride anions
in aqueous solutions consisting of 9/1 (v/v) H2O/DMSO (pH
4.8). Fluoride sensing, which rests on the formation of the fluorostiboranes 2–F and 3–F, is accompanied by
a distinct turn-on fluorescence response. This response is especially
marked upon conversion of [3]+ into 3–F, with a fluorescence intensity enhancement by ∼8
fold and a quantum yield of 59.2% for 3–F. The
relevance of this study is established by demonstrating that [3]+ can be used as a selective fluoride sensor
for bottle or tap water.