Study On Synthesis And Recognition Effect Towards Metal Ions Of Fluorine-Containing Coumarins

Coumairn moiety has been found to be used in the fields of biology, medicine, perfumes, cosmetics, and laser dyes. The structure of benzopyrone has many advantages including high fluorescence quantum yield, large Stokes shift, excellent light stability, and less toxicity. Coumairn moiety became excellent fluorophore in molecular design for fluorescence chemosensor. By far coumarin derivatives used as fluorescent probes had become hot investigation.Based on reading a larg number of literatures, the paper discussed the synthesis and application in fluorescence chemosensor of coumarin derivatives, and the route for synthesis of novel fluorescence chemosensors based on coumarins containing trifluoromethyl are described in detail. Coumarins containing trifluoromethyl reported were mostly 4- trifluoromethyl coumarins synthesized through Pechmann reaction between phenols and compounds containing trifluoromethyl. In our previous work, we designed to gain 3-trifluoroacetylcoumarins. Because carbonyl in trifluoroacetyl group is more reactive than that in ester group, Knoevenagel condensation did not produce 3-trifluoroacetylcoumarins (1) directly, but 2-hydroxyl-2-trifluoromethyl-3- ethoxycarbonyl-2H-1-chromenes (1). Then we treated chromene 1 with TsOH-H2O (2 mol%) in chlorobenzene to afford coumarin 2 in high yield. Finally, the novel fluorescent probes (3-12) were prepared from coumarin (2a) with compounds containing amino in chlorobenzene for 0.5-6 h.The structures of the new compounds were characterized with 1H NMR,13C NMR,19F NMR, MS, IR and single crystal X-ray diffraction. The reaction conditions were studied in order to find the optimal one of high yield. The absorption and fluorescent emission spectras of typical compounds were tested and analysized, and the fluorescent quantum yields were calculated too.The absorption and emission spectra of chemosensor 9,11 and 12 upon addition of equal equivalent different metal ions (Mg2+, Zn2+, Ca2+, Cu2+, Ni2+, Hg2+, Co2+, Fe3+, Al3+) were tested respectively. Upon addition of Cu2+ or Ni2+ to 11, a blue shift or a bathochromatic shift of the absorption band was observed while the emission band blue-shifted with decrease in the fluorescence intensity. In the presence of Cu2+ the color of the solution of 11 changed from orange to red obviously. Therefore 11 could be used as an optical chemosensor for Cu2+ with high sensitivity.