Properties Of Crystallization,Aggregation-induced Emission And Mechanochromic Luminescence Of Pyridyl β-Diketone

Fluorescent materials is widely used in many fields such as chemistry, materials science, bioscience, medical science, environics because of high sensitivity, high selectivity, trace monitoring of fluorescence analysis. During the past decades, there has been a dramatic growth in the theory and use of fluorescence, and there is no longer the need for the expense and difficulties of handling fluorescent measurements.Fluorescence technology is used from many disciplines and the principles of fluorescence is described to help us understand the microworld better, study fluorescent materials further, optimize the performance of materials and enlarge the application of them since fluorescence spectrum could provide information of molecule progress.Herein, I focused on the research in the properties of crystallization, aggregation-induced emission and mechanochromic luminescence of pyridyl P-diketone fluorescent materials. The sol-gel-sol transformations of polyacrylates bearing dinitrobenzoate side groups were also studied.At the beginning, 1-(4-Methoxyphenyl)-3-(2-pyridyl)-1,3-propanedione(M1), 1-(4-Methoxyphenyl)-3-(3-pyridyl)-1,3-propanedione(M2), 1-(4-Methoxyphenyl)-3-(4-pyridyl)-1,3-propanedione(M3) were synthesized respectively. Crystal morphology of M1 is curving. It is so different from regular crystal morphology of M2 and M3. It is more likely to the difference of position of N atom substitution. Crystallization condition including concentration of solution and solvents used was studied and no correlation between them was found. In addition, the energy of ground-state of pyridyl β-diketones was calculated by molecular dynamics simulation. The result suggests that enol form is more stable due to the lower energy of planar construction. Crystallization process and π-π stacking was also simulated. The direction of methoxy group is always outward and three-molecule ring emerges according to the calculated result. Single crystal X-ray diffraction measurements of them were conducted to shed light on the bent crystal because H of enol of M2 and M3 are on the molecular plane while H of M1 is not. It means M1 is a chiral molecule.Furthermore, a series of pyridinium ring substituted β-diketones were found to exhibit aggregation-induced emission (AIE) and water-vapour recoverable mechanochromic luminescence in the solid state. Certain watersoluble β-diketones could selectively bind to cellulose-based materials, where strong fluorescence similar to AIE was turned on.Finally, polyacrylates bearing dinitrobenzoate side groups undergo sol-gel-sol transformations in DMF or THF solutions regulated by alternating UV light and dark conditions. The formation and recombination of radical ionic species via photoinduced electron transfer may be responsible.