Design And Synthesis Of Novel Xanthene Dyes And Its Derivatives For Sensing Hg²⁺

Recently, fluorescence imaging has become one of the most effective techniques for monitoring biomolecules and their physiological process in living systems, while fluorescent probes with superior performance lay the most solid foundation for imaging analysis. Xanthene dyes is universally used in fluorescent probes because of their outstanding photophysical properties. Unfortunately, there are still some problems to constrain their applications seriously. Firstly, most of fluorescent probes were obtained by special and complex routes, therefore, designing more probes that can be synthesized easily is quite significant. Secondly, most probes were excited in the visible region, which restrict their applications in the field of cell biological markers. The third drawback of xanthene dyes is their small Stokes shifts, which can cause detection error due to Rayleigh scattering effects and serious quenching. In this thesis, we focuses on innovation of the structure of xanthene dye, design and synthesis of a series of novel xanthene dyes, aimed at cracking the nuts in construction and application, around this purpose, we have carried out the following works:(1) We design and synthesize a Rhodafluor isomer R, which has two hydroxyl moieties substituted at para-position insteadly. Next, we explore the spectroscopic properties of R in different organic solvents. R showed a distinct absorption band and fluorescence emission only upon addition of TFA or in water, which demonstrated that R transformed into a ring-opening form in acidic solvent. Both absorption spectra and emission spectra had some red shift in water, and the Stokes shift of R is also longer. It was emphasized that R is keeping a stable optical signals over a wide p H span of 3-11, indicating that R has great potential applications in cell biomarkers. The different modificability on the hydroxyl groups and carboxy group are also carried out successfully and three derivatives R1、R2 and R3 were obtained. They can function as highly selective fluorescent probes for sensing Hg2+.The association constants of the three probes were 1.10×104 M-1(R = 0.991)、2.72×105 M-1(R = 0.996)、1.27×103 M-1(R = 0.992) respectively,and the detection limit were estimated to be 3.32×10-9 M、8.82×10-7 M、2.66×10-6 M。(2)Based on the above design strategy, we synthesize another three novel xanthene dyes X、Y and Z, their scope of p H in water were 3-10、4-10 and 3-11, and they have good cell membrane permeability. Finally, We design a fluorescent probe Z1 with high selectivity and sensitivity for sensing Hg2+,and the association constants is 4.53×103 M-1(R = 0.991), the detection limit is 4.36×10-8 M。Conclusively, we synthesize four novel xanthene dyes, construct a series of fluorescent probes for sensing Hg2+. The main purpose is placed on the design of the structure of xanthene dyes, to conquer the bottle-necks in the development of fluorescent probes.