"Off-on" aggregation-based fluorescent sensor for the detection of chloride in water.

Receptors selective for anions in aqueous media are a crucial component in the detection of anions for biological and environmental applications. Recent sensor designs have taken advantage of systems known to aggregate in solution, eliciting a fluorescent response. Herein, we demonstrate a chloride-selective fluorescent response of receptor 1(+), based on our well-established class of 2,6-bis(2-anilinoethynyl)pyridine bisureas. The fluorescence intensity ratio of 1(+)·Cl(->) aggregates in water is four times larger than the next most fluorescent anion complex, 1(+)·ClO4(->). In addition, (1)H NMR spectroscopic titrations demonstrate 1(+) binds chloride more strongly than other biologically relevant anions in solutions of both DMSO-d6 and 50/50 DMSO-d6/MeCN-d3.