A ratiometric chemosensor for fluorescent determination of Hg(2+) based on a new porphyrin-quinoline dyad.

Quinolin-8-ol p-[10',15',20'-triphenyl-5'-porphyrinyl]benzoate (1) was synthesized for the first time and developed as a ratiometric fluorescent chemosensor for recognition of Hg(2+) ions in aqueous ethanol with high selectivity. The 1-Hg(2+) complexation quenches the fluorescence of porphyrin at 646nm and induces a new fluorescent enhancement at 603nm. The fluorescent response of 1 towards Hg(2+) seems to be caused by the binding of Hg(2+) ion with the quinoline moiety, which was confirmed by the absorption spectra and (1)H NMR spectrum. The fluorescence response fits a Hill coefficient of 1 (1.0308), indicating the formation of a 1:1 stoichiometry for the 1-Hg(2+) complex. The analytical performance characteristics of the chemosensor were investigated. The sensor shows a linear response toward Hg(2+) in the concentration range of 3x10(-7) to 2x10(-5)M with a limit of detection of 2.2x10(-8)M. Chemosensor 1 shows excellent selectivity to Hg(2+) over transition metal cations except Cu(2+), which quenches the fluorescence of 1 to some extent when it exists at equal molar concentration. Moreover, the chemosensor are pH-independent in 5.0-9.0 and show excellent selectivity for Hg(2+) over transition metal cations.