Design,Synthesis And Application Of Pyridinium Salts With Aggregation-Induced Emission Characteristics

Fluorescence analysis has the advantages of simple operation,high sensitivity,good selectivity,low detection limit,and can be used for cell or in vivo imaging.However,most fluorescent probes suffered from the aggregation-caused quenching（ACQ）effect,which greatly limits their applications.Aggregation-induced emission luminogens（AIEgen）can effectively overcome the ACQ effect of traditional fluorescent probes.In addition,fluorescent probes with AIE feature have the advantages of good photostability,low background fluorescence,and high sensitivity,and thus are widely studied in sensing,imaging and disease diagnosis and therapy.However,most AIE-active fluorescent probes still have poor water solubility,AIEgens with pyridinium pendant usually have good water solubility.The strong intramolecular donor-acceptor（D-A）interactions,can promote the red shift of the emission wavelength of AIE probes,and reduce the interference of autofluorescence.Moreover,positive charged pyridinium compounds also have the ability to target subcellular organelles.Based on these considerations,here in this dissertation,we designed and synthesized a series of AIE-active fluorescent probes with pyridinium pendant that can selectively detect Pd⁰ or Hex,We also explored the protein photocleaving ability of AIEgen modified porphyrin derivatives.The main results are as follows:1)A novel and simple light-up fluorescent probe（PASPy-al）with a D-π-A structure based on AIE as well as ESIPT processes was designed for highly selective discrimination of Pd²⁺and Pd⁰.PASPy-al displayed a large Stokes shift（95 nm）,a high light-up ratio（116 fold）and a low limit of detection（LOD:96 n M）toward Pd⁰.Moreover,the practical applications of PASPy-al for detection of Pd⁰ in environmental,human urine and pharmaceutical samples were realized.Fluorescence imaging of Pd⁰ in live cells was realized by using PASPy-al.Furthermore,imaging of Pd⁰ generation in live cells was also realized by in situ reduction of Pd²⁺to Pd⁰ in the presence of reducing agent like CO,indicating the potential ability of this probe for further fluorescent imaging of cellular reducing agent.The easy preparation of probe PASPy-al plus their excellent parameters would make it a simple to handle probe for detection of Pd⁰ both in practical samples and in live cells.2)A lysosome targeting light up AIE-active fluorescent probe（GlcNAc-TPE）was fabricated with remarkably large Stokes shift（252 nm）,high sensitivity and selectivity towardβ-N- acetyl-hexosaminidases（Hex）.GlcNAc-TPE can selec-tively locate in lysosome and visualize endogenous Hex in live HCT116 cells and in live mice with high stability and good biocompatibility,providing a useful AIE probe for real-time visualization of Hex in live samples.3)An AIEgen decorated porphyrin（TPETPyP）was easily obtained through a one-step reaction.The bulky TPE in TPETPyP greatly impeded the intermolecularπ-πstacking of the porphyrin core,which significantly suppressed ACQ effect of TPETPyP in aqueous solution.The four pyridinium salts formed in TPETPyP also render the whole molecule water solubility,which eliminated its aggregation.TPETPyP exhibited ¹O₂ quantum yield as high as 0.85 in PBS.Moreover,it also showed high binding affinity to proteins,the major biotarget of ¹O₂.The high ¹O₂ quantum yield plus the great binding ability of TPETPyP toward proteins makes it a highly-efficient protein photocleaving agent.Protein electrophoresis experiments demonstrated that TPETPyP can photocleave BSA upon visible light irradiation,indicating that TPETPyP can act as a promising photosensitizer（PSs）in photodynamic therapy（PDT）. The work here will provide a facile strategy to utilize AIEgen modified traditional PSs for PDT.