Study On The Synthesis Of Rhodamine Dyes And Their Applications As Fluorescent Probe

As one kind of the xanthenes,rhodarnine dyes are widely used in the fields of chemical and biological analysis because of their unique character& Today,the fluorescent analysis of ions and molecular based on revised rhodamine dyes is developing to high selectivity,high sensitivity and fluorescence imaging in cells Based on these published results,a series of rhodamine dyes with active groups using in biology and fluorescent sensors with high sel ectivity for metal ions were designed and synthesized.Six rhodamine dyes with different substituents in phenyl contraposition were designed and synthesized based on different substituent benzaldehyde as raw materials.Through altering synthesis method,the products were sole,avoiding the production of isomers mixture. The spectral results showed that the changes of molar extinction coeffidents were i ndepended upon proton and aprotic solvents,which avoided fluorescent quenching in aprotic solvent made by lactonic form of traditional rhodarnine B dyes.Finally,the photostabilities of these dyes were investigated.Compared with traditional rhodamine dyes,these dyes were found to have the same good photostabiliti es as that of traditional rhodami ne dyes.Based on "Off-On" fluorescent switch principle,three fluorescent probes have been designed and synthesized.RhoCr1 showed can selectively recognize Cr³⁺in Tris-HCI neutral buffers through the absorption and emission spectrum.The coordi nation of RhoCrl with Cr³⁺ was a reversible process through RhoCrl with Cr³⁺and TPEN titration experirnent.Moreover, the recognition of RhoCr1 for Cr³⁺was further proved by simulative way which reduced Cr⁶⁺ in K₂Cr₂O₇ to Cr³⁺and coordinated with RhoCr1.The fluorescence images that RhoCr1 coordinated with Cr³⁺in PC12 cells showed RhoCr1 to be capable of penetrating into living cells and imaging intracellular Cr³⁺changesFive probes have been designed and synthesized,where different aldehydes were covalently linked to rhodamine B dyes with diethylamine flexible chains.The selectivity in aqueous and organic solution was studied through their UV-Vis absorption and emission spectra.The results indicated that selectivity for Cr³⁺or Fe³⁺were different with substituents in aldehyde& The pyridine and amido would like to improve coordination affinity for Cr³⁺. The thi ophene and hydroxyl would refer to coordi nati on wi th Fe³⁺.Four fluorescent probes Rh6GFe1,Rh6GFe2,Rh6GFe3 and Rh6GFe4 based on rhodamine 6G were designed and synthesized.In tris-HCI neutral buffers,Rh6GFel displayed an excellent selectivity for Fe3 over the other metal ions and a strong fluorescence appeared.Upon addition of saturating Fe³⁺,the fluorescence intensity enhanced nearly 70-fold. By using fluorescence microscopy of Hele cells and PC12 cells,probe Rh6GFe1 was shown to be capable of penetrating into living cells and imaging intracellular Fe³⁺distribution. Fluorescent probes Rh6GFe2,Rh6GFe3 and Rh6GFe4 by using thiophene-2-carboxaldehyde, pydine-2-carboxaldehyde and 2-hydroxybenzaldehyde as chelaters for metal ions were pH-independent in the range of pH5-9.Their pK_a value were 3.76,3.82,3.77 respectively. Through linear titration and Ka calculation,these probes could detect for Fe³⁺at the level of micromole.