A ratiometric chemosensor for fluorescent determination of Hg2+ 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 Hg2+ ions in aqueous ethanol with high selectivity. The 1-Hg2+ complexation quenches the fluorescence of porphyrin at 646 nm and induces a new fluorescent enhancement at 603 rim. The fluorescent response of 1 towards Hg2+ seems to be Caused by the binding of Hg2+ ion with the quinoline moiety, which was confirmed by the absorption spectra and H-1 NMR spectrum. The fluorescence response fits a Hill coefficient of 1 (1.0308), indicating the formation of a 1:1 stoichiometry for the 1-Hg2+ complex. The analytical performance characteristics of the chemosensor were investigated. The sensor shows a linear response toward Hg2+ in the concentration range of 3 x 10(-7) to 2 x 10(-5) M with a limit of detection of 2.2 x 10(-8) M. Chemosensor I shows excellent selectivity to Hg2+ over transition metal cations except Cu2+, which quenches the fluorescence oft 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 Hg2+ over transition metal cations. (C) 2009 Elsevier B.V. All rights reserved.