| Recently, the research of fluorescent materials with aggregation-induced emission (AIE) property provides rich theories for scientific workers. Currently, workers mainly focus on restricting intramolecular nonradiative decay by physical or chemical methods, promote the radiative decay and obtain excellent fluorescent materials with AIE property. However, their application in organic light emitting diode (OLED), chemical probes, biological sensor and other areas still exists much restriction. We utilized benzoxazole and isophorone as building blocks, designed and synthesized a series of heterocyclic compounds with AIE activity. We also explore their potential application in cell imaging. Self-assembly of part of the ligands with metal salts yielded a series of new coordination complexes.The main achievements in the dissertation are listed as follows:(1) We accomplished the synthesis and characterization of three Schiff base compound (L1-L3) based on benzoxazolyl system. We changed the position of nitrogen atom in pyridine and obtained that these Schiff base derivatives all show excellent AIE property. At the same time, we also comparatively investigated their emissions in solution, mixed solution, powder and crystal states. According to the dynamic light scattering (DLS), scanning electron microscope (SEM), transmission electron microscope (TEM) and crystal structure, we discovery that these compounds will form less-crystalline or even amorphous but more-emissive nanoparticle by abrupt aggregation in mixed solution with large amounts of water, which effectively prevent or avoid π-π stacking.(2) We also synthesis the Schiff base L4-L6 based on benzoxazole system by introduction of hydroxylphenyl and diethylaminophenyl groups, and these compounds also exhibit AIEE property. Interestingly, L5 not only exhibits the change in fluorescent intensity (389 nm), but also big change in emission wavelength with a new emission wavelength (542 nm). L6 also shows big redshift of 70 nm. Such ratiometric fluorescence changes with large red-shifts of 150 and 70 nm for L5 and L6 in benzoxazole-based compounds have so far never been reported. According to their crustal structure, SEM and et al, we summarize that the restricted intramolecular motions and coplanarity induced by aggregation well explain the AIEE behavior and the impressive color change of L4 and L6. The crystal structure of L5 indicate that it belongs to H-aggregate and the effective emission of L5 in nanoparticle, powder, crystal states can also attribute to H-aggregate, which is different from the traditional understanding of H-aggregates. The specific slip-stacking and the dimer formed by multiple intermolecular interactions avoid strong H-type coupling and are responsible for highly emissive H-type aggregates.(3) We introduced ethyl-cyanoacetate as the terminal substituent of isophorone derivatives instead of malonitrile based on our previous works and synthesis a new isophorone family (2a-2e).2a-2d exhibit obvious AIE/AIEE phenomena, while 2e shows fluorescence quenching in the aggregate state. The morphology and size of aggregates with different water contents were investigated using SEM and DLS, indicating that a large number of smaller globular or quadrate nanoparticles with average diameters in the range 78.79-392.7 nm in mixed solutions are related to these AIE/AIEE or ACQ behaviors. We also made comparative analyses of their optical properties in different states. The crystal data of 2a-2d reveal that the multiple intra-and intermolecular interactions lead to the molecular conformation being more stable, increase the planarity of compounds, restrict the intramolecular motions, and promote the formation of J-type aggregate, enabling chromophores 2a-2d to emit intensely in the solid state. In addition, the frontier molecular orbital energy and band gap calculated by density functional theory are quite consistent with the experimental results. Finally, these AIE/AIEE-active compounds could be used in bioimaging applications, which immensely provide a new strategy to the application of some AIE/AIEE systems.(4) By self-assembly of L、L5、L7 with different copper salts, dinuclear copper compex (1) based on Cu(OAc)2, dinuclear copper coordination polymer (2) based on CuCl2, and three benzoxazolyl-copper(Ⅲ,Ⅱ,Ⅰ) complexes (3-5) based on CuBr2 were obtained. The Schiff base L5 and L7 decompose into amino and aldehyde groups under the Lewis Cu2+. CuBr2 acts as catalyst to catalyze aryl carbon-hydrogen bromination reaction in the process of coordination. On the basis of the above depicted works and the related literatures, we speculated and proposed the mechanism for the bromination reactions. Finally, the magnetic properties studies indicate that there exists the antiferromagnetic interaction in 2 and provide the magnetic data fitted by PHI program in the 2-300 K range with the following parameters:J=-2.68 cm-1, g1＝g2＝2.15. |
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