A chelation enhanced selective fluorescence sensing of Hg2+ by a simple quinoline substituted tripodal amide receptorElectronic supplementary information (ESI) available: Characterization data for 1,2 and 3 copies of 1H NMR, 13C-NMR, HRMS (ESI-MS) and IR spectra. See DOI: 10.1039/c1dt10923e

Two tris(2-aminoethyl)amine (tren) based tripodal amide fluoroionophores, 1 and 2 , functionalized with quinoline (chelating fluorophore) and naphthalene (non-chelating fluorophore) respectively, are synthesized in good yields. Fluoroionophore 1 shows a selective UV-Vis spectral shift in the case of Hg 2+ in acetonitrile among different metal ions like Li + , Na + , Ca 2+ , Mg 2+ , Cr 2+ , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Hg 2+ , Pb 2+ , and Ag + . On the other hand, fluoroionophore 2 shows no selectivity towards any of the above metal ions in the UV-Vis study. Furthermore, 1 shows a selective chelation induced fluorescence enhancement in the presence of Hg 2+ whereas 2 shows the enhancement of fluorescence with most of the metal ions via a photoinduced charge transfer mechanism. The naked eye detection of Hg 2+ in an acetonitrile solution of 1 shows a greenish fluorescence upon UV light irradiation. The isolated Hg 2+ complex of 1, 3 , shows a similar UV-Vis and fluorescence spectral output as observed from in situ spectroscopic studies of 1 in the presence of Hg 2+ . Infra-red (IR) and 1 H- NMR studies also reveal the interaction of Hg 2+ with the quinoline nitrogen atoms as well as with the amide functionality. A simple tripodal amide based chelating fluoroionophore 1 shows selective UV-Vis spectral shift and a chelation induced fluorescence enhancement in the presence of Hg 2+ over the other metal ions.