| AIE has been greatly developed in the last decade. Thanks to RIR, RIM mechanism, AIE phenomenon and AIE molecular design become easy to understand. AIE materials have involved in the frontier of display, illumination, detection and Photodynamic therapy. However, AIE system also has some disadvantages, such as low molecular planarity, single light, and short-wavelength emission. In this article, new AIE molecules were synthesized and investigated. Some functionality explorations were studied. Through data and theory analysis, this thesis summarizes some of the structure-property relationship, which can guide the design of the molecules.Firstly, a set of salicylaldehyde imines with AIE + ESIPT property was synthesized. Structure-property relationship was studied. The electron withdrawing group on the phenol ring strengthens the hydrogen bond, and reduces the energy gap between enol and keto. As a result, energy coupling between two excited states gets easier. The effect of intramolecular hydrogen bond is to lock the intramolecular rotation and-C=Nisomerization, and is a key role for fluorescent performance and the AIE phenomenon. The donor group, methoxyl, is likely to exhibit the characteristics of electron-withdrawing to some extent, and partially offset the conjugated electron-donating effect.Secondly, in the study of salicylaldehyde imines shows that the hydrogen bond plays an important role in the inhibition of the twisting and isomerization of the molecules. Hence, a set of boranil derivatives was designed. Boron atom replaces hydrogen atoms to further inhibit the motions above. The effect of positions and substituents on the fluorescence of the compounds was investigated. Some clues of structure-property relationship have been gained: 1) The impact of the position effect of substituent on the emission wavelength is larger than the electronic effect. 2) The compounds are ACQ as the substituent on the 5-position, regardless of donor or acceptor group. 3) The compounds are AIE(CIE) as methoxyl on the 4- or 6-position. 4) Electronic effects in the system are not the most direct factor affecting emission. The origin of difference between ACQ and AIE(CIE) comes from the packing and the interaction of molecular orbit.Thirdly, a set of Chalcone with AIE+ESIPT+DA property was synthesized. Guiding by the structure-property relationship achieved above, the emission performance of the compounds is highly improved. Further structure-property relationship was investigated, through the discussion of spectroscopy, crystal structure, electronic effect of substituents and planarity of the molecule. As compounds with the same crystal structure, the difference of fluorescence is from the electronic effect of the substituent, which makes it possible to show the impact of electronic effect quantitatively. As compounds with almost the same planarity and electronic effect, the different emission property is from the packing and the horizontal distance between stacked molecules.Finally, in addition to the simple application of the ion detector, the novel thermoresponsive AIE polymers with fine-tuned response temperature were prepared in this work. It combines the RIR mechanism of AIE and the responsive mechanism of traditional thermosensitive polymer(PNIPAM). As the temperature increases and chain shrinks, AIE unit is squeezed and turned on. A third monomer(OEGMA or MMA) is copolymerized into the polymer, and offers it the property of fine-tuned response temperature. A preliminary study of its application in cell imaging and lifetime imaging indicates the potential for biological applications.It is no doubt that structure-property relationship can provide guidance for the molecular design, which is valuable. |
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