Preparation And Fluorescence Properties Ofβ-diketo-based Fluorescent Chromotropic Materials

Materials with mechanofluorochromic properties have been widely studied in the fields of optoelectronics,bioengineering,mechanical sensing and anti-counterfeiting materials due to their unique photoelectric properties and sensitivity to mechanical forces.With the development of science and technology,the requirement for the properties of these materials is higher and higher.β-diketone itself has luminescent properties,the fluoroboron complexes formed byβ-diketone and boron trifluoride ether have excellent photoelectric properties,and the luminescent color can be changed with the introduction of different groups and the change of the way of molecular packing,which is a research hotspot in this field.In this paper,three types ofβ-diketone fluoroboron complex based on tetrastyrene group were designed and synthesized.The first kind is the complexes with tert-butylene,p-methyl,cyano and trifluoromethoxyl as the end of the molecule.The UV absorption spectra showed that the maximum absorption peaks of the complexes with different groups were different.The weak absorption peaks in the spectra were caused byπ-πtransition,and the strong absorption peaks were caused by electron transfer.The fluorescence emission spectra of the complexes in the mixed solvent of H₂O/THF showed that the fluorescence emission intensity of the complexes increased with the increase of water content,and the maximum emission wavelength of the complexes was found to be redshifted.This is due to the aggregation of the complexes molecules with the increase of water content.It also shows that the complexes have AIE characteristics.The fluorescence emission spectra of solid powder before and after grinding showed that the fluorescence emission wavelength of the ground solid powders had obvious red shift,and the ground solid powders can be recovered by solvent dichloromethane fumigation.The maximum fluorescence emission wavelength of the complexes with different groups was also different.The more planar the molecular structure was,the more obvious the red shift of the maximum fluorescence emission wavelength was.The mechanofluorochromic properties of solid powders were caused by the transformation between crystalline state and amorphous state of the complexes.It was also found that the polymer materials prepared by physical blending of molecular dyes and LDPE also exhibited mechanofluorochromic property.The second kind of molecules is tetraphenyleneβ-diketone fluoroboron complex with different alkyl chains as molecular ends.The UV absorption,AIE characteristics and mechanofluorochromic properties of these molecules were investigated,and the mechanofluorochromic properties of polymers containing these molecules were also investigated.The fluorescence emission wavelength of these molecules changed little before and after grinding in solid state.The third kind of molecules is tetraphenylvinylfluoroboron complexes with different aromatic ring structures as molecular ends.The mechanofluorochromic properties of these complexes have also been studied.It is found that these molecules were more sensitive to force,the solid powder discoloration was easier by grinding,and the splines prepared by blending with LDPE also exhibited mechanofluorochromic properties.The above results showed that the three kinds of complexes possessed AIE characteristics and mechano-fluorescence discoloration characteristics.The mechanism of discoloration is due to the transformation between crystalline state and amorphous form of the complexes.The samples prepared by blending the three kinds of complexes with LDPE also possess mechano-fluorescence discoloration characteristics.