Study On Synthesis And Recognition Effect Towards Ions Of Coumarin-Based Fluorescent Probes

Coumarin derivatives owe their importance to their sufficient fluorescence in the visible light range, large Stocks shift, high quantum yield of photoluminescence and reasonable solubility, which gives rise to one of the most extensively investigated and commercially significant organic fluorescent materials. By far coumarin derivatives used as fluorescent probes had become hot investigation.In this work 3-trifluoroacetyl-7-hydroxycoumarin was synthesized by using ethyl trifluoroacetoacetate and 2,4-dihydroxybenzaldehyde as starting materials in the presence of piperidine as catalyst. The hydroxy group at 7-position of the coumarin was alkylated to afford new 3-trifluoroacetyl-7-alkyloxycoumarins.Based on reading a larg number of literatures, the paper discussed the synthesis and application of coumarin derivatives as fluorescence chemosensors. The routes to synthesis of novel fluorescence chemosensors based on coumarins containing trifluoromethyl group are described in detail. Coumarins containing trifluoromethyl reported were mostly 4-trifluoromethyl coumarins synthesized through Pechmann reaction between phenols and compounds containing trifluoromethyl group. In our work, we designed to synthesize 3-trifluoroacetylcoumarins by a two-step protocol and Knoevenagel reaction.The structures of the new compounds were characterized with 1H NMR,13C NMR, LC-MS, IR. The reaction conditions were studied in order to achieve high yields. The absorption and fluorescent emission spectra of typical compounds were tested and analysized. The fluorescent quantum yields of the coumarin dyes were calculated.Upon addition of equal equivalent different metal ions (Mg2+, Zn2+, Ca2+, Cu2+, Ni2+, Hg2+, Co2+, Fe3+, Al3+) the difference in the absorption and fluorescent spectra of the sensors were tested. Addition of Cu2+ or Ni2+ brought marked changes to both the absorption spectra of 11# sample while other metal ions did not cause distinct change in the spectra of 11#. Meantime, addition of equal equivalent different anonic ions (NO2-, F-, HSO3-, Cl-, HSO4-, AcO-, NO3-) to 9#,11# and 12# samples decreases the fluorescent intensity dramatically.