Glutamine-containing "turn-on" fluorescence sensor for the highly sensitive and selective detection of chromium (III)...

In this study, we reported a new fluorescence sensor for chromium (III) ion, dansyl-L-glutamine (1). The sensor displayed a unique selective fluorescence "turn-on" response to Cr(3+) over other common metal ions in water. Notably, 1 still showed a ratiometric response to Cr(3+) in UV-vis absorption spectra. The binding mechanism of 1 to Cr(3+) was further clarified by using NMR and ESI-MS spectra. The experiment results indicated that the dual-responses of 1 to Cr(3+) should attribute to the coordination of deprotonated sulfonamide group with Cr(3+) and the protonation of the dimethylamino group due to the coordination of Cr(3+) for 1. In addition, two chloride ions also coordinated to the complex of sensor-chromium (III) ion, which further strengthened the conformation of 1-Cr(3+).