Rhodamine 6G-based Chemosensor for the Visual Detection of Cu 2+ and Fluorescent Detection of Hg 2+ in Water

A novel water soluble chemosensor 1 based on rhodamine 6G spirolactam scaffold has been synthesized and characterized. Upon addition of a wide range of the environmentally and biologically relevant metal ions, chemosensor 1 shows a colorimetric selective Cu2+ recognition from colorless to pink confirmed by UV-Vis absorption spectral changes, while it also exhibits a fluorometric selective Hg2+ recognition by fluorescence spectrometry. An absorption enhancement factor over 17-fold with 1-Cu2+ complex and a fluorescent enhancement factor over 45-fold with 1-Hg2+ complex were observed. Their recognition mechanisms were assumed to be a 1:1 stoichiometry for 1-Cu2+ complex and a 1:2 stoichiometry for 1-Hg2+ complex, respectively, which were proposed to be different ligation leading to the ring-opening of rhodamine 6G spirolactam. Furthermore, the detection limits for Cu2+ or Hg2+ were 3.3×10−8 or 1.7×10−7 mol/L, respectively.