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A quinoline-vinyl-dihydroxylphenyl linkage comprising a donor-π-bridge-acceptor structural motif, in which the quinoline serves as an electron-withdrawing core, has been synthesized and used as a fluorescent sensor ( 2 ) for the recognition of Al 3+ and F − by colorimetry/fluorescence. The sensor 2 exhibited little fluorescence due to excited-state intramolecular proton transfer from the hydroxyl oxygens to the nitrogen of the quinoline moiety. By contrast, on coordination of Al 3+ or F − , sensor 2 afforded strong fluorescence. A reversible “off–on” optical switching mode has been constructed by sequential inputs from Al 3+ and F − ions to the sensor 2 via different excitation and emission wavelengths. 1 H NMR and IR spectroscopic analysis revealed that the Al 3+ is coordinated to the quinoline nitrogen and phenolic oxygen atoms, whereas the F − center is only coordinated by two phenolic oxygen atoms. [ABSTRACT FROM AUTHOR]

A novel quinoline-functionalized hexahomotrioxacalix[3]arene L was synthesized via Click chemistry and its chemosensing properties with various metal ions were investigated. The chemosensor L exhibited a high selectivity for Fe 3+ with little interference from other environmentally and biologically relevant metal ions, leading to a prominent ‘off-on’ type fluorescent signalling behaviour. Our studies demonstrated that the detection limit on fluorescence response of the sensor to Fe 3+ is in the 10 −7 M range. The mechanism of the interaction between the L and Fe 3+ has been investigated in detail by 1 H NMR spectroscopic titration experiments. [ABSTRACT FROM AUTHOR]