The Design, Synthesis And Application Of Novel Schiff Bases Fluorescent Probes

Fluorescent probes have attracted more attention of many researchers, because they can convert molecular recognition informations into fluorescent signals depend on their high sensitivity and selectivity, and also attribute to their in-situ analysis in living cells. Small organic molecules fluorescent probes are research focus in the area of biological analysis and chemical fields in recent years due to their simple structure, easier synthesis methods, better properties and lower costs.Rhodamine B and BODIPY are widely applied to the design and synthesis of the fluorescent probe because of their excellent performances. Rhodamine B has high molar extinction coefficient and high fluorescent quantum yield, lower toxicity and good water-solubility. More importantly, it can synthesize “Off-On” fluorescent probe depend on the spiral structure of rhodamine B. BODIPY fluorophore has better photostability, insensitive to the polarity of solvent and pH, high molar extinction coefficient, lower toxicity, high fluorescent quantum yield, easy to modify and so on. Hence, we designed and synthesized three fluorescent probes which could recognize Cu²⁺ and pH, HOCl and Au³⁺, respectively.In chapter 2, a dual-function optical chemosensor?RBF? was designed and easily synthesized by condensation reaction of 5-Hydroxymethylfurfural and rhodamine B hydrazide. RBF exhibited highly sensitive, highly selective and quick response to acidic pH. The fluorescence intensity of RBF exhibited a more than 41-fold increase within the pH range from 7.50 to 3.73, which could be successfully applied to monitor intracellular pH in living PC12 cells and HeLa cells. Additionally, the spectroscopy of UV-Vis and EDTA-adding experiments indicated that RBF was a highly selective and reversible colorimetric chemosensor for Cu²⁺. Moreover, RBF has been successfully applied to detect Cu²⁺ in real water samples.In chapter 3, a highly selective and sensitive boron-dipyrromethene?BODIPY? based fluorescent probe?Bodipy-Hy? for the detection of hypochlorous acid?HOCl? was designed and easily synthesized by the condensation reaction?C=N? of BODIPY aldehyde?BODIPY-AL? and hydrazine hydrate, which contain a newer group compared with other similar probes. With the specific HOCl-promoted oxidation grade of the C=N bond increasing, the fluorescence intensity of Bodipy-Hy gradually increased more than 11-fold. And the fluorescent quantum yield enhances from 0.06 to 0.62. A linear increase of fluorescence intensity could be observed under the optimum conditions with increasing HOCl concentration over a wide linear range 0-22.5 mM, then a lower detection limit of 56 nM based on 3×?blank/k was obtained. Moreover, the probe can also be successfully applied to imaging HOCl in living cells with low cytotoxicity.In chapter 4, we designed and synthesized a mono-Schiff-base fluorescent probe?Probe1? based on a boron-dipyrromethene?BODIPY? dye. By investigating the recognition of Au³⁺ through an irreversible C=N bond hydrolysis reaction, Probe 1 exhibited higher properties such as acting as a “naked eye” probe, stability to p H, fast-response of 90 s, a lower detection limit of 60 n M and stronger antijamming capability compared with other probes. Even in relatively high temperatures, Probe1 maintained its own excellent characteristic. Significantly, this is the first time that one chemosensor could be successfully applied to Au³⁺ imaging in zebrafish, which demonstrated the performance that Probe1 exhibited wonderful organism permeability.