New Fluorescent Probes Based On Naphthalene And Tetraphenylethene Derivatives

Metal ions, anions and some small molecules play an important role in theenvironment and bio-physiological system. They are closely linked with the health ofthe organism, some are highly toxic and some are involved in many essentialphysiological processes in vivo. Therefore, many researchers are working on researchand development the various ways to detect ions and small molecules inenvironment and the living body.Fluorescent molecular probes for its detection of low cost, high sensitivity, lowsample consumption, simple operation, etc., have been widely used in envir onmentalscience, medicine, materials science, biology and others. And they have gotten a gooddevelopment. However, the most reported fluorescent probes have poor watersolubility, and exhibit short absorption and emission wavelengths in the visible range,and aggregated easily lead to fluorescence quenching and other shortcomings.Accordingly, it is desirable to develop novel fluorescent probes to overcome theselimitations, making them promising probes for analytes in biological system.Therefore, in order to improve the wave length, aggregation easily leading tofluorescence quenching and other shortcomings of the fluorescent molecular probes.We designed and synthesized three kinds of fluorescent probes for H₂S, Al³⁺and ClO^-.The contents of this thesis are presented as follows:1. H₂S is the third endogenously generated gaseous signaling compound, and hasalso been known to involve in a variety of physiological processes. To betterunderstand its physiological and pathological functions, efficient methods formonitoring of H₂S in living systems are desired. Although quite a few one photonfluorescence probes have been reported for H₂S, two-photon probes are morefavorable for intracellular imaging. In chapter2, by employing aDonor-Acceptor-structured naphthalene derivative as the two-photon fluorophore andan azide group as the recognition unit, we reported a new two-photon bio-imagingprobe NB1for H₂S with improved sensitivity. The probe shows very low backgroundfluorescence in the absence of H₂S. In the presence of H₂S, however, a significantenhancement for both one photon and TP excited fluorescence were observed,resulting in a high sensitivity to H₂S in aqueous solutions with a detection limit of20nM observed, much lower than previously report ed TP probe. All these features are favorable for direct monitoring of H₂S in complex biological samples. The probe canselectively image endogenous and exogenous hydrogen sulfide in living cells by usingtwo-photon fluorescence confocal microscopy, demonstrating its value of practicalapplication in biological systems.2. Aggregation-induced emission （AIE） dyes show different emission mechanismfrom traditional dyes, which were found nonluminescent in the solution state butemissive in the aggregate state, and have been well employed to design turn-onfluorescent probes for various targets. In chapter3, we for the first time reported atetraphenylethylene-based AIE probe1for Al³⁺, which employed twodiethylenetriamine units as recognition ligand for Al³⁺. In the presence of Al³⁺, a largefluorescence enhancement was achieved for probe1, which together with the lowbackground fluorescence of free probe1allow for a high sensitivity for Al³⁺, with adynamic range from2.010-6to1.110-5M observed. The proposed probe alsoshows a high selectivity to Al³⁺. UV-Vis absorption spectra experiments and dynamiclight scattering measurements were performed to verify the AIE sensing mechanismof probe1. Moreover, a1:1stoichiometry was estimated for the1-Al³⁺complex viafluorescence Job’s method.3. In chapter4, Fluorescein semicarbazide （FS） was synthesized and developedas a novel fluorescent probe for the highly selective and rapid detection ofhypochlorite （ClO^-） in aqueous solution. It was found that FS is nonfluorescent inbuffer solution at physiological pH7.4, but ClO^-selectively and rapidly transforms itinto a fluorescent product. Fluorescence enhancement resulted from the formation offluorescent fluorescein-1,3,4-oxadiazole by a ClO^--promoted desulfurization andcyclization reaction. It can be seen that FS only is nonfluorescent, but isNaClO^-selective, leading to an appearance of green fluorescence. In contrast, otherspecies such as H202、 OH、O2-、NO2-、NO、1O2and TBHP did not induce obviousfluorescence enhancement. The results presented in this work may contribute to thedevelopment of new analytical methods and the design of new fluorescent probes thatare suitable for ClO^-detection in physiological environments.