hg cn 2 is the most toxic and hazardous mercury compound, and its accumulation in organs and tissues is known to cause significant health problems. It is mainly found in the kidney and other tissues of the human body, but it is also toxic to the brain and liver.

Various fluorescent probes have been developed for the sensing of CN- and Hg2+, with the goal of reducing environmental and health risks caused by these chemicals. In addition, some of these sensors are reversible and can be applied in the analysis of real water samples.

For example, Zhou and co-workers 104 developed a fluorescent probe based on benzo-BODIPY with a carboxyl-thiol metal bonding receptor for Hg2+. The emission intensity of this molecule increased significantly with the addition of Hg2+. This fluorescence “turn-on” was probably due to the PET process quenching of the benzo-BODIPY fluorophore by the electron-donating nitrogen atom from the carboxyl-thiol.

In another example, Wang and co-workers53 synthesized indole derivatives bearing cyanide (CN-) and fluoride (F-) salts as receptor units. Compound 14 exhibited a strong absorption band at 456 nm, which decreased upon the addition of CN-. This led to the formation of a new absorption peak at 503 nm, generating an isosbestic point and change in color from yellow to red.

Similarly, 91 a and 91 b, synthesized by Piyanuch and co-workers in 2019, were able to detect CN- and Hg2+ in an aqueous medium using NIR (near infrared) emission and chelation-enhanced fluorescence (CHEF). The LMCT (ligand-mediated phototransduction) phenomenon occurred between the chemosensor molecule 91 and the ions with a 1 : 1 binding stoichiometry according to Job’s method. The LOD was 8.4 x 10-8 M for 91a and 5.9 x 10-9 M for 91b in MeCN : H2O and DMSO : HCl (100 : 100 mM) buffer solutions.

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