Ratiometric fluorescence chemosensor based on tyrosine derivatives for monitoring mercury ions in aqueous solutions

Ratiometric fluorescent chemosensors 1 and 2 were synthesized based on tyrosine amino acid derivatives with a pyrene fluorophore. 1 and 2 showed high selectivity for Hg(ii) ions among 13 metal ions in aqueous solutions. Both 1 and 2 sensitively detected Hg(ii) ions in aqueous solutions by ratiometric response without interference of any of the other tested metal ions including Cu(ii), Cd(ii), Pb(ii), and Ag(i) ions. 1 and 2 had tight binding affinities (5.72 × 10¹³ M^-2, 1.15 × 10¹³ M ^-2) for Hg(ii) with nano-molar detection limits. The binding mode was characterized with the help of organic spectroscopic data, which revealed that the methoxyphenyl moieties of 1 and 2 played a vital role in the coordination of Hg(ii). The deprotonation of the sulfonamide group is not a critical process for the binding of mercury ions. The methoxyphenyl moiety, sulfonamide group, and the C-terminal amide moiety of 1 and 2 as ligands for Hg(ii) played crucial roles in the stabilization of the 2:1 complexes. This journal is