| Owing to the advantages of simple synthesis and easy modification,Schiff base compounds have been studied extensively in catalysis,corrosion,medicine and other traditional industries.In particular,Schiff base compounds with differential responses to different metal ions have shown promising application prospects in the field of new optoelectronic materials due to their superior photophysical properties and coordination abilities.However,for Schiff base molecules,how to enhance the performance in these fields by improving the optical properties and response behaviors to metal ions still needs further systematic research.To solve the above problem,a series of Schiff base compounds with different photophysical properties and metal ion response behaviors were designed and synthesized by controlling fluorophore,receptor,and spatial configuration with imine bond（-RC=N-）orientation as the entry point.The fluorescence properties and response mechanisms of these materials were investigated in depth,and their applications in smart probe,optoelectronic device and information storage were also explored.The main work includes the following four parts:（1）A design strategy for constructing intelligent responsive Schiff base molecules by regulating the orientation of imine bond was proposed.Two well-known highly twisted luminogens tetraphenylethylene（TPE）and triphenylamine（TPA）derivatives and a linear2-phenylthiophene were selected as fluorophores.Three groups of phenolic Schiff base isomers were designed and synthesized distinguished by the imine bond orientation relative to fluorophore by using salicylaldehyde and o-aminophenol.By the crystallographic data analysis,it was found that N=C oriented Schiff bases（1-3NC）with fluorophores on the N side had intramolecular hydrogen bonds,while C=N oriented Schiff bases（1-3CN）with fluorophores on the C side did not.By the comparison of the optical properties in aggregate and solid state,it was found that N=C oriented Schiff bases exhibited typical aggregation-induced emission（AIE）properties,while C=N oriented Schiff bases showed fluorescence inactivity in solution and solid.By the characterization of responses to metal ions,it was found that N=C oriented Schiff bases showed similar quenching responses to Cu2+and Fe3+,while C=N oriented Schiff bases realized the“turn-on”cyan fluorogenic response to Al3+(λem=492 nm),and the“turn-on”orange fluorogenic response to Zn2+(λem=592 nm).Based on this significantly differentiated fluorescence properties caused by different imine orientations,N=C oriented Schiff bases can be applied to fabricate light emitting diodes（LEDs）,and C=N oriented Schiff bases can be used as intelligent fluorescent probes for multiple metal ions.（2）Based on the differential response behaviors of C=N oriented Schiff bases to metal ions,to further investigate the influence of fluorophore change on response behaviors,by selecting 2-pyridylthiophene as the fluorophore,a C=N oriented aminophenol Schiff base named NOS with multiple potential coordination sites was designed and synthesized.It was found that NOS could coordinate with multiple metal ions to afford mononuclear tridentate complexes.These complexes exhibited differential responses of five colors and three types of fluorescence depending on the metal ions.Based on the diverse response behaviors,by using metal ion solutions as security inks and tetrabutylammonium fluoride（TBAF）as an eraser,rewritable multi-color storage and colorful fluorescence storage were realized on the papers modified by NOS and polyethylene glycol（PEG）.In addition,based on the differential optical properties of NOS complexes,multiple encryption plans including primary encryption,secondary encryption,and composite encryption were proposed and implemented.Moreover,using water and temperature to regulate the coordination between NOS and Mg2+,the rewritable water-jet information storage was realized.（3）To investigate the influence of receptor change on response behaviors,by selecting benzothiazole as the receptor and TPA as the fluorophore,a C=N oriented Schiff base TPA-BTS was designed and synthesized.By the spectra characterization,it was found that TPA-BTS exhibited the chromogenic response from colorless to red to Cu2+(λabs=505nm)and the blue fluorogenic response to Fe3+(λem=468 nm)in acetonitrile,and exhibited the green fluorogenic response to Zn2+(λem=536 nm)in aqueous solution.Based on the differential responses,TPA-BTS was used as an intelligent fluorescent probe for Cu2+,Fe3+,and Zn2+with detection limits as low as 0.45,3.24,and 3.22μM,respectively,and was employed in real water sample detection.In addition,test strips made of TPA-BTS were implemented for portable detection of Zn2+.（4）To investigate the influence of molecular configuration on response behaviors,by selecting TPA,bithiophene,and 2-phenylthiophene as fluorophores and benzothiazole as the receptor,three C=N oriented Schiff base TPA-BTS,Th-BTS and Ph-BTS with different spatial configurations were designed and synthesized,respectively.By the absorption spectra characterization,the planar Schiff base Ph-BTS was found to have the best precipitation response with a precipitation rate of 95.4%.The precipitate（Ph-BTS-Ag）exhibited good antibacterial activity against S.aureus,E.coli and P.aeruginosa.Based on these results,Ph-BTS was employed as a selective precipitant and realized the conversion of Ag+in wastewater into antibacterial materials by one step.In addition,by the PL spectra characterization,Ph-BTS exhibited the blue fluorogenic response to Fe3+(λem=445 nm),and exhibited the green fluorogenic response to Zn2+(λem=524 nm)triggered by 365 nm irradiation.Based on the differential responses,Ph-BTS was used as an intelligent fluorescent probe for Fe3+and Zn2+.Meanwhile,it was found that the complex formed by Ph-BTS and Zn2+（Ph-BTS-Zn）exhibited a reversible cis-trans isomerization under light irradiation with different wavelength,accompanied by the change from fluorescence quenching to green fluorescence turning on.Based on this phenomenon,Ph-BTS-Zn can be used to construct a new type light-controlled rewritable information storage medium. |
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