Synthesis And Properties Of Chiral Fluorescent Materials

Chiral fluorescent functional materials have broad application prospects in biosensing,bioimaging,optical storage devices and optoelectronic devices.As an important class of chiral fluorescent functional materials,chiral organic luminescent materials have attracted wide attention due to their clear structure,easy derivation and high luminous efficiency.At present,researchers have developed a variety of chiral organic luminescent materials based on central chiral,planar chiral,axial chiral and helical chiral structures.These chiral organic light-emitting materials have excellent fluorescence efficiency and high luminescence asymmetry factor in solution,but the fluorescence quantum yield in solid or aggregated state is generally low,which limits their practical application.Therefore,it is of great significance to design and develop novel chiral organic fluorescent materials with high luminous efficiency in solid or aggregated state.In this paper,the fluorescence intensity was enhanced by introducing different substituents on the tetrahelicene,and four groups,p-methoxystyrene,p-cyanostyrene,styrene and 4-vinylpyridine,were introduced respectively.The structure of the product was determined by NMR and mass spectrometry,and its spectral properties were determined by UV fluorescence.It is found that the first four pairs of compounds studied in this paper have multiple UV absorption peaks in different solvents,which is caused by the particularity of the helicene structure.The fluorescence emission spectra of the four compounds all show double emission peaks,which is because one peak is excited by the ground state and the other is excited by the charge transfer state.The aggregation-induced luminescence effect of cyanostyrene and styrene is good.All four compounds have the highest fluorescence quantum yield in dimethyl sulfoxide.It is particularly noteworthy that the liquid fluorescence quantum yield is high and the solid fluorescence quantum yield is high.It is also very high.Among them,the liquid fluorescence quantum yield and the solid fluorescence quantum yield are the highest for p-methoxystyrene,which are as high as 45% and 67.7% respectively.The CD signals are all in good mirror symmetry,and only compound p-methoxystyrene has circularly polarized luminescence(CPL)signal.In addition,four pairs of axial chiral fluorescent molecules with benzoxazole or benzoquinoxalinone structures were synthesized on the basis of chiral binaphthol(BINOL).The correct structure of the compound was determined by NMR and mass spectrometry.Its spectral properties were studied by UV absorption spectroscopy,fluorescence emission spectroscopy,and CD tests.The two pairs of compounds introduced with benzoxazole have aggregation-induced luminescence properties.When the water content of the compound introduced with monobenzoxazole is 60%,the fluorescence intensity is the strongest,and the fluorescence intensity is enhanced to about 10 times.When the water content of the azole compound is 60%,the fluorescence intensity is enhanced to about 8 times.The two pairs of compounds introduced into benzoquinoxalinone can adjust their fluorescence intensity under acidic conditions.The CD signals of the four pairs of compounds showed good mirror symmetry.