| The discovery of curcumin has a history of more than 250 years.Studies have found that curcumin and its analogs have a variety of biological activities such as anti-oxidation,anti-inflammation,anti-tumor,and blood lipid reduction.In recent years,they have also been widely used as fluorescent dyes and probes.It is worth noting that when the β-diketone structure in curcumin is further converted into a borofluoro complex,a larger conjugation system is formed,which causes redshift of fluorescence emission.Therefore,as a new type of long-wavelength-emitting fluorophores,curcumin difluoroboron β-diketone complexes have also been widely used in photodynamic therapy and bioimaging.For example,curcumin difluoroboron β-diketone complexes have been applied to label β-amyloids in Alzheimer’s disease.Over the past few years,research on curcumins and their difluoroboron complexes have become an emerging research hotspot in the field of organic fluorescent materials.However,curcumindilfluoroboron complexes have limited structural diversity.In addition,their these molecules only have moderate fluorescence quantum yields due to the π-conjugation system,which has push at both ends and pull in the middle.In the preliminary research of this thesis,we noticed that because curcumin difluoroboron β-diketone complexes also have electron push-pull and π conjugation structure as cyanine dyes,they exhibit high similarities in their physical properties and fluorescence characteristics,such as long-wavelength emission and high molar extinction coefficient.However,they have minor differences in their Stokes shifts.Therefore,the focus of this thesis is the design and synthesis of a series of novel fluorophores with the combined structural characteristics of both curcumin difluoroboron β-diketone complex and cyanine.These novel fluorophores are expected to have the properties of long-wavelength fluorescence emission,increased the fluorescence quantum yields,large Stokes shifts and high structural derivatization capabilityChapter 2 of this thesis includes the synthesis of dimethylamino-and diphenylamino-containing curcumin analogs along with their difluoroboron complexes and the determination of their solution/solid(crystal)fluorescence properties;Chapter 3 includes the synthesis of a series of novel difluoroboron β-diketone complexes,and studies on their fluorescence properties and applications in bioimaging;Chapter 4 includes the synthesis of a series of novel β-diketone complexes with solid fluorescence and studies on their solution/solid fluorescence properties.The details research work are described as follows.In Chapter 2,4 amine-containing curcumin analogs and their difluoroboron β-diketone complexes were synthesized according to the methods reported in literature.The single crystals of two curcumin analogues were obtained for the first time and their solution and solid fluorescence properties were determined.Experimental results show that the solution fluorescence of this series of molecules exhibits typical twisted intramolecular charge transfer(TICT)characteristics.Analysis of the crystal structures of curcumin analogs reveals that the substituents on the amino group(methyl and phenyl)have significant effect on the molecular packing.The diphenylamino group’s negative effect on molecular coplanarity results in the enhanced solid-state fluorescence of the corresponding molecules.Similarly,diphenylamino-based curcumin dilfluoroboron β-diketonecomplex exhibits remarkable solid-state fluorescence characteristics as well.In addition,the results of this study also laid the foundation for the subsequent design and synthesis of novel difluoroboron β-diketone complexes and the study on regulating their solid-state fluorescence via structural modifications.In Chapter 3,firstly,a prototype difluoroboron β-diketone complex fluorophore with the structral features of both dimethylamino-based curcumin)and N-methylbenzothiazolium-based cyanine was designed and synthesized.The solution-phase fluorescence properties of the fluoropohore was determined.The results show that the compound is a long-wavelength emitting fluorophore with high fluorescence quantum yield and large Stokes shift.According to the established synthetic method,another 4 difluoroboron β-diketone complexes containing N-methylbenzothiazolium and N-methylquinolinium substituents were designed and synthesized.Moreover,another 2 fluorophores with extended conjugation chains and further red-shifted fluorescence emission were synthesized.The evaluation of their photophysical properties show that these new compounds are a class of long-wavelength-emitting fluorohores with excellent fluorescent properties.Bioimaging experiments show that this type of new fluorophores are low toxic,can effectively enter cells,and stain a specific organelle,the endoplasmic reticulum.Therefore,it appears as a new type of endoplasmic reticulum red fluorescent probe.In Chapter 4,on the basis of the effects of diphenylamino group on the coplanarity and solid-state fluorescence of curcumin difluoroboron β-diketone complexes,phenyl groups ewere introduced to different positions of the novel difluoroboron β-diketone complex fluorophores.Two novel borane β-diketone compounds were designed and synthesized.The experimental results of their solution/solid photophysical properties show that this series of fluorophores still have high fluorescence quantum yields in solution,indicating that the introduced phenyl groups do not dissipate excited state energy through rotation.At the same time,due to the influence of the phenyl substituents on the coplanarity of the molecule,this series of compounds all exhibit significant red solid-state fluorescence... |
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