A rhodamine-based fluorescent chemsensor for Hg(II) with high selectivity in solution

A fluoresencent chemsensor (compound 1) for the detection of Hg2+ ion was designed and synthesized. This sensor was prepared by incorporating the well-known Rhodamine 6G fluorophore and the 2-pyridinecarbaldehyde binding unit into one molecule. The structure of 1 was fully characterized by H-1 NMR, ESI-HRMS and X-ray crystallographic analyses. The emission properties of compound 1 were investigated in a mixed aqueous environment. Upon addition of Hg2+ ion, the emission increased accompanied by a color change from colorless to pink. It exhibited a high selectivity for Hg(II) even over a complicated background of excess other metal ions as potential competing species. The metal-binding properties of 1 were studied by fluorescent titration, ESI-HRMS and Job's plot analysis. All the studies suggest a 1:1 stoichiometry for the 1 center dot Hg complex. CCDC: 717917.