Study On Synthesis And Application Of Thiocarbonyl Coumarin-based Fluorescent Probes For Mercury Ion

Fluorescent chemosensors are highly valuable in a variety of fields including environmentalchemistry, analytical chemistry, and bio-medicinal science. Coumarin fluorescent probe belongs toa kind of fluorescent chemosensors. In the last decades, coumarin fluorescent probes have drawnmuch attention of the researchers for their high fluorescence quantum yield, large Stokes shift,excellent light stability, and less toxicity.In this paper, the progress in research of fluorescent probes was summarized, the principle offluorescent probes operation was interpreted. Furthermore, the advances in the synthesis ofcoumarin compounds and the application of fluorescent probes in detecting mercury ion werereviewed.Herein a series of new chemosensors for Hg (II) ions based on3-ethoxycarbonyl and3-aminocoumarin containing thiocarbamide group were synthesized. The probe molecules9,21,24and29were based on3-ethoxycarbonyl coumarin as matrix, reacting with hydrazine hydrate to gethydrazide coumarin, by reacting the nucleophilic substitutions with phenyl isothiocyanate to getformamide phenylthiocarbamide coumarin probe, The probe molecules15and18were based on3-amino coumarin as matrix, reacting with phenyl isothiocyanate to generate phenylthiocarbamidecoumarin probe. Introduction of the phenylthiocarbamide group into coumarin led to excellentacid and alkali resistance of the probes. The introduction of thiourea group is in favor of thereactions of complexing, ligand and desulfurizationand with mercury ion. So to introduce thisgroup on the coumarin matrix can improve the performance of the coumarin fluorescent probe. The structures of the new compounds were characterized with IR,1H NMR,13C NMR, MS. Theoptimum reaction conditions have been researched and obtained.Four typical fluorescent probe molecules were selected for test. The acid and alkali resistance,sensitivity, selectivity of the sensors to Hg (II) were investigated which based on UV-visabsorption spectra and fluorescence emission spectrum. Results of the tests show that3-ethoxycarbonyl coumarin,3-amino coumarin and other thiourea classes coumarin fluorescentprobe can be used to identify Hg2+with high sensitivity and high selectivity. The probes6-substituent of formamide phenylthiocarbamide21and24have very good detection effect onmercury ion only in0.2equivalent, which showed a very good detection sensitivity. The testprocess also found that3-phenylthiocarbamide coumarin probes9,15and18not only have highsensitivity but also has high acid and alkali resistance. They can be used in the applicable pHrange between1.73to12.45, They can be stable in a wide range of pH solution and can be appliedin the special environment of the Hg2+detection.