Effects Of Side-chain Substituents And Substrates On Mechanochromic Luminescence Properties And Design And Development Of Long-life Luminescent Materials

In the past few decades, organic fluorescent and phosphorescent materials have broad important applications in the mechanical sensing, organic optoelectronics,biological imaging and other fields. In the face of broad application prospects, more and more scientific research workers are committed to developing more efficient luminescent materials to meet the needs of multiple fields. Focus on academic hotspots, I am devoted to the study of the mechanism of mechanochromic luminescence and the development of long-life luminescent materials during the course of my Ph.D. study. Specific work is as follows:1. We have designed and successfully synthesized three types of fluorinated and non-fluorinated long-chain alkyl-substituted pyrene derivatives to provide some preliminary clues for the design principles in terms of the effect of substituents and substrates as well as to explore the possibility of real application of mechanochromic luminescent materials. The effects of side-chain substituents and substrates on mechanochromic luminescence properties were verified by fluorescence spectroscopy, differential scanning calorimetry, single crystal and powder X-ray diffraction. Different side-chain substituents, mono- or polysubstituted of the same side-chain group have a significant effect on the luminescent properties (e.g., mechanochromic luminescence properties) of fluorophores (e.g., pyrene); the strong interaction between the dye and the substrate allows the dye to be randomly distributed at the molecular level to affect the mechanochromic luminescence properties. Weak dyes-substrates interactions and strong dye-dye interactions may be the best way to design functional mechanochromic luminescence systems.2. We designed and synthesized seven kinds of fluorophore-quencher dyad (FQD), and explored the effect of the linker, donor and acceptor on the luminescent properties caused by intermolecular charge transfer. We found that the electronegativity and the interaction intensity of the linker affect the occurrence of intermolecular charge transfer by means of fluorescence spectroscopy; Simple combination chemistry does not necessarily screen out FQD molecules with high quantum yields, the combination of donor and acceptor gives the molecular structure that the crystal stacking arrangement is conducive to the occurrence of charge transfer. Finally, the room temperature phosphorescence long-life luminescent molecules with 23.6%quantum yield were selected by simple and efficient synthesis.3. We designed and synthesized the pyridine-substituted P-diketone, and found that its crystals exhibit a curved fractal structures under an optical microscope. In order to understand this phenomenon,we designed structurally related diketones and compared the difference between the crystal morphology. We also explored the intrinsic mechanism of pyridine-substituted ?-diketone PBDK1 forming a curved fractal structure by changing the type of solvent, the rate of solvent volatilization,and the initial concentration of PBDK1. Finally, the single crystal X-ray diffraction test revealed that PBDK1 in the process of crystallization due to weak intermolecular interactions, molecules are easier to slip and dislocation,and ultimately lead to irregular crystal structure. Finally, We have demonstrated the application of using these naturally generated crystal patterns in fashion design.