Design,synthesis And Properties Of Novel Organic Molecular Fluorescent Probes Based On The Structure Of Coumarin

Due to its high selectivity,high sensitivity,in-situ real time and no invasive fluorescence monitoring,the fluorescent probe technique has a great application value in environmental chemistry,analytical chemistry,biological medicine science et al.Coumarin and its derivatives have a variety of physiological activities,for example,anti-tumor,antihypertensive,antioxidant and so on.They have also many good optical properties,such as high fluorescence quantum efficiency,large Stokes shift,good solubility,good light stability,etc.They have been widely used in the design of fluorescent probes.3-Hydroxycoumarin is an important organic synthesis intermediate,however,the fluorescent properties of 3-hydroxycoumarin were rarely reported in literatures.Furthermore,3-hydroxycoumarin is never used in the design of fluorescent probes.In this dissertation we designed and synthesized two novel fluorescent molecules through introducing different electron-donating substituents at position 7 of the skeleton of 3-hydroxycoumarin.Four fluorescent probes for thiols were developed by introducing different recognition groups at the hydroxyl site of3-hydroxycoumarin derivatives.These probes were evaluated for their sensing ability and then applied to real samples.The specific contents include the following:In Chapter 2,we firstly synthesized a novel fluorescent dye,7-diethylamino-3-hydroxy-coumarin?HOCOU-DA?,which had a good property of fluorescence.The2,4-dinitrophenyl?DNP?and 2,4-dinitrobenzenesulfonyl?DNS?as strong electron withdrawing groups were incorporated at 3-hydroxy of HOCOU-DA respectively.The DNP ether and DNS ester were decomposed in the presence of thiophenols through the reaction of nucleophilic aromatic substitution,releasing the free fluorophore,HOCOU-DA,thus resulting in an increase in fluorescence.Thus we designed and synthesized two turn-on fluorescent probes for detecting thiophenols,DNCOU-DA and DOCOU-DA.These two probes featured remarkable large Stokes shift?DNCOU-DA:98 nm,DOCOU-DA:113 nm?,and showed highly selective and sensitive detection processes for thiophenols.The limits of detection of probes were calculated as low as 27 nM?DNCOU-DA?and 7.3 nM?DOCOU-DA?for thiophenols.Finally,the actual applications of the two probes were illustrated by the detection of thiophenols in real environmental water samples.In Chapter 3,we synthesized a novel fluorescent dye,10-hydroxy-coumarin 6H?HOCOU?.A fluorescent probe for thiophenols?DNCOU?was produced by the introduction of DNP at the hydroxyl of HOCOU.The probe featured a high selectivity toward thiophenols with a large Stokes shift?128 nm?and the limit of detection was calculated as low as 36 nM.The probe was also successfully applied for quantitative detection of thiophenols in real water samples and fluorescent thiophenols imaging in HepG2 cells.In Chapter 4,a fluorescent probe based on HOCOU has been designed and synthesized to detect biothiols.The sensing mechanism involves the nucleophilic attack of biothiols on the DNS ester,releasing the attached fluorophore,thus leading to the recovery of fluorescence.The probe exhibited remarkably selective fluorescence enhancement with a 130 nm Stokes shift in buffer media.The limits of detection of the probe were very low(LOD_Cys=17.1 nM,LOD_GSH=14.5 nM,LOD_Hcy=40 nM).The probe which had very weak cytotoxicity to HeLa cells was successfully applied for fluorescence imaging of biothiols in HeLa cells.