Two novel fluorescent probes based on phenothiazine: synthesis and “naked-eye” colorimetric recognition of Hg2+

Two novel colorimetric and fluorescent probes 2-(1,3-dithiolanes)-10-ethyl phenothiazine (PHE–Ed) and 2-(1,3-dithianes)-10-ethyl phenothiazine (PHE–Pd) based on phenothiazine were successfully synthesized, and their structure was confirmed by NMR and high resolution mass spectra. Fluorescence investigations revealed that the synthesized probes could be used for the selective detection of Hg2+, which was accompanied with an obvious color change from colorless to light yellow. The applicable ability of the two probes was investigated by a series of competitive experiments, solid colorimetric experiments, and applied experiments, which proved that these probes showed high sensitivity and great potential to detect Hg2+ in environmental analysis systems. Furthermore, the detection mechanism of the probes was investigated by FT-IR spectra and NMR spectra, and the results indicated that the detection of Hg2+ was accomplished through the Hg2+-promoted deprotection of thioacetal.