Crown Ether Benzoxazolyl-Alanines as Fluorimetric Chemosensors for the Detection of Palladium in Aqueous Environment

Palladium has wide application in different contexts and, as a consequence, high levels of palladium in the environment have been reported, representing a risk to human health. Considering the interest to develop more selective and sensitive chemosensors for this analyte, two novel benzoxazolyl-alanine derivatives bearing a crown ether moiety were studied as potential fluorimetric chemosensors for palladium detection. Preliminary chemosensory studies for these unnatural amino acids in the presence of selected metal cations were performed in acetonitrile solution and in aqueous mixtures of sodium dodecyl sulfate (SDS, 20 mM, pH 7.5) solution with acetonitrile, 90:10 v/v. In acetonitrile solution, these probes had a fluorescence response for different cations but, most importantly, in SDS aqueous solution both compounds displayed a selective fluorescence response in the presence of palladium.