Synthesis And Aggregates Emission Behavior Of Cyanostilbene Derivatives

Organic small molecular optical materials have been attached much attention due to the exact structure,easy purification and functionalization and excellent self-assembly properties.However,they are usually suffered from strong intermolecular interactions and charge transfer that lead to them weak even non-emission in solid state.Recently,a number of organic small molecular optical materials with excellent properties have been reported.Especially,the reports of aggregation-induced emission?AIE?and aggregation-induced emission enhancement?AIEE?compounds open a new way for design and synthesis fluorophores with high solid emission.But the luminous efficiencies of most AIE/AIEEgens are not ideal.The relationships between the aggregates structures and properties are also need to be further investigated.Cyanostilbene derivatives are representative AIEEgens.They provide many advantages for developing excellent AIEE materials and studying the AIE mechanism as the AIEE active properties,simple prepare procedure and multiple self-assembly types.In this work,a series of cyanostilbene derivatives with excellent properties have been designed and synthesized based on full literature research.The relationships between structure and property and the AIE mechanism are investigated through spectra analysis,crystal structure analysis and theoretical calculations.Meanwhile,the materials were applied in emission color tuning,luminous liquid crystal and fluorescence probe according to the structure and property characteristic.The main research contents were as follows:1.Conterion controlled molecular aggregates and AIEE properties Organic salts have advantages for controlling molecular aggregates structures.The photophysical properties could be tuned by both their cation and anion constituents.In this work,four cyano substituted styrene pyridiniums?PyC1,PyNO3,PyOTs and PyPh4B?with different anions have been designed and synthesized and the effect of anions on the structure and property are studied.In dilute organic solution,the molecules are free that the anions have negligible influence on their photophysical properties since the same fluorophore.However,their solid emission is different with the increasing of anionic volume,from Cl-,NO3-to OTs-,the fluorescence wavelength gradually blue-shifted from bluish-green to deep blue and the fluorescence quantum yields increase from 2.5%to 13.1%.Interestingly,the PyPh4B with the largest anion is non-emission in solid.Crystal and DFT studies reveal that the enhanced fluorescence is ascribed to the formation of dimers and bigger anions induce larger molecular separation in dimers.Meanwhile,this unique dimeric packing endows the crystal of PyNO3 with anisotropic fluorescence.2.Side chain controlled molecular aggregates and AIEE propertiesThe non-conjugate groups could control the molecular packing arrangements that change the AIEE properties.A series of D-?-A type cyanostilbene derivatives?ZH,ZOM,ZOE and ZOB?with different side chain have been synthesized by "one pot"method.The structures were full characterized.The effect of side chain on the free and aggregations state properties are studied by UV-Vis and fluorescence spectra.The results showed that side chain has negligible influence on free molecular properties and deeply affect the aggregations state properties.ZH no side chain is weak emission both in solution and solid state.ZOM,ZOE and ZOB modified side chain are AIEE active that weak emission in solution but emission enhancement in aggregations state.The relationships between structure and property were further investigated by crystal structure analysis.The results show that the ?-system of ZH has no interactions.After functionalized side chain,ZOM forms H-dimer aggregates.ZOE and ZOB form J-aggregates that extend the electron delocalization which enhance the solid fluorescence.3.End alkyl chain controlled AIEE and liquid crystal propertiesDeveloping luminous liquid crystal materials could solve the problems of liquid crystal non-emission to simplify device structure,reduce production cost and energy consumption and enhance brightness and contrast.Indolo[3,2-b]carbazole derivatives have excellent luminescent properties.In this work,the indolo[3,2-b]carbazole and cyanostilbene unit were combined in one molecule and further modified by end alkyl chain to obtain three indolo[3,2-b]carbazole derivatives?ZY4,ZY8 and ZY12?with different end alkyl chain.The structures were characterized in detail.The effect of end alkyl chain on the free and aggregations state properties and liquid crystal properties were studied.The results revealed that end alkyl chain had negligible influence on free molecular photophysical properties and affect the AIEE properties.All the compounds are AIEE active.The solid fluorescence quantum yields are gradually enhancement and the emission wavelength red-shifted with the increasing of alkyl chain.ZY12 has liquid crystal properties and shows obvious luminous anisotropy.Meanwhile,the emission of ZY12 liquid crystal device was decreased in electric field indicated it had the potential application in electric field response device.4.Design and synthesis of Hg²⁺ induced-aggregation fluorescence probeTwo Schiff base modified cyanostilbene derivatives fluorescence probes?TS and Zl?have been designed and synthesized based on the chelating ability of Schiff base and the AIEE properties of cyanostilbene derivatives.The structures were characterized in detailed.Both compounds are AIEE active that the fluorescence not quenched in aquatic environment.The coordination of probe molecules with Hg²⁺ as the chelation properties induces the formation of aggregates that enhanced the emission.Furthermore,Zl could detect the Hg²⁺ in HepG2 cell by fluorescent confocal microscopy.