A reversible ESIPT based system for the detection of Hg2+ was developed. The system exhibited better properties compared to that of recently developed ratiometric fluorescent systems.

No abstract

Iodine-methanol mediated oxidative-aromatization of 2-aryl-6,8-dibromo-2,3-dihydroquinolin-4(1H)-ones afforded the corresponding 2-aryl-6,8-dibromo-4-methoxy-quinolines in high yield and purity. The isomeric 1-(2-amino-3,5-dibromophenyl)-3-aryl-2-propen-1-ones reacted with iodine in methanol afford in a single pot operation the corresponding 2-aryl-6,8-dibromo-4-methoxyquinoline (major) and 2-aryl-6,8-dibromoquinolin-4(1H)-one (minor) products that were separated in sequence by column chromatography on silica gel. Suzuki-Miyaura cross-coupling of the 6,8-dibromo-4-methoxyquinoline derivatives with excess arylvinylboronic acids afforded the corresponding 2-aryl-6,8-bis(2-arylethenyl)-4-methoxyquinolines. The absorption and fluorescence properties of these compounds were also determined.

We describe a new fluorescent polymer system based on a coumarin-triazole functionality. The non-fluorescent 3-azidocoumarin-alkyne monomers are polymerized in a step-growth manner via a Cu (I)-catalyzed 1,3-dipolar cycloaddition (CuAAC) reaction. The process involves the conversion of a quenching azide group to 1,2,3-triazole in the monomer that leads to an increase in the intensity of fluorescence in the new polymer. The solubility and photophysical properties of the polymer were enhanced through co-polymerization with an aliphatic co-monomer. KEYWORDSCoumarin, poly(coumarin-triazole), click polymerization, solubility, photophysical properties.

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.

A highly sensitive coumarin-based on–off system for the detection of Cu2+ in water was developed. The system was successfully applied for the detection of Cu2+ at micromolar levels in natural water samples.

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Two coumarin derivatives containing triazole moieties have been synthesized using "click chemistry" protocol and investigated as chemosensors for the detection of metal ions. These compounds displayed a strong preference for Fe 3+ ions with complexation resulting in fluorescent quenching. The detection limit of the preferred chemosensor was determined to be 1.4 µM. The preferred triazole-coumarin compound showed greater selectivity towards Fe 3+ in the presence of competing metal cations. Binding stoichiometry between this triazole-coumarin and Fe 3+ was shown to occur in a 1:1 ratio between the chemosensor and metal cation. The binding site of Fe 3+ to the triazole-coumarin was determined using 1 H NMR, 13 C NMR and molecular modeling studies.