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A novel fluorescent polymer for Hg2+ recognition was developed based on the phototautomerism mechanism of 7-hydroxycoumarin in aqueous solution. The developed system showed higher sensitivity and specificity towards Hg2+ in the acetonitrile/water mixture over various other metal ions, with a significant fluorescence quenching of the main emission band. It was shown that the presence of Hg2+ affects the chemical equilibrium of the 7-hydroxycoumarin phototautomers through the excited state intramolecular proton transfer (ESIPT) mechanism, which results in ratiometric fluorescence response upon stepwise addition of Hg2+. The occurrence of ESIPT mechanism was explained based on a comparison of the 1H NMR spectra of the starting alkynylated coumarin (4) in a non-polar aprotic solvent (CDCl3) and in a polar aprotic solvent (DMSO-d6). This was further confirmed by 1H NMR of 4 upon stepwise addition of Hg2+ in a polar aprotic solvent (DMSO-d6). From titration experiments, a higher sensitivity with a detection limit at the nanomolar level (50 nM) was observed and the response was fast and reversible. The real applications of the developed system were investigated in real samples and satisfactory results were obtained for both fresh and lake water samples. [ABSTRACT FROM AUTHOR]

A novel fluorescent polymer with pendant triazolyl coumarin units was synthesized through radical polymerization. The polymer showed reasonable sensitivity and selectivity towards Cu2+ in acetonitrile in comparison to other tested metal ions with a significant quenching effect on fluorescence and blue shifting in the range of 20 nm. The blue shift was assigned to the conformation changes of the diethylamino group from the coumarin moiety which led to planarization of the triazolyl coumarin units. The possible binding modes for Cu2+ towards the polymer were determined through the comparison of the emission responses of the polymer, starting vinyl monomer and reference compound, and the triazole ring was identified as one of the possible binding sites for Cu2+. The detection limits of the polymer and vinyl monomer towards Cu2+ were determined from fluorescence titration experiments and a higher sensitivity (35 times) was observed for the polymer compared with its starting monomer. [ABSTRACT FROM AUTHOR]

A novel fluorescent polymer for Hg2+ recognition was developed based on the phototautomerism mechanism of 7-hydroxycoumarin in aqueous solution. The developed system showed higher sensitivity and specificity towards Hg2+ in the acetonitrile/water mixture over various other metal ions, with a significant fluorescence quenching of the main emission band. It was shown that the presence of Hg2+ affects the chemical equilibrium of the 7-hydroxycoumarin phototautomers through the excited state intramolecular proton transfer (ESIPT) mechanism, which results in ratiometric fluorescence response upon stepwise addition of Hg2+. The occurrence of ESIPT mechanism was explained based on a comparison of the 1H NMR spectra of the starting alkynylated coumarin (4) in a non-polar aprotic solvent (CDCl3) and in a polar aprotic solvent (DMSO-d6). This was further confirmed by 1H NMR of 4 upon stepwise addition of Hg2+ in a polar aprotic solvent (DMSO-d6). From titration experiments, a higher sensitivity with a detection limit at the nanomolar level (50 nM) was observed and the response was fast and reversible. The real applications of the developed system were investigated in real samples and satisfactory results were obtained for both fresh and lake water samples. [ABSTRACT FROM AUTHOR]