Design,Synthesis And Sensing Application Of Molecular Probes With Aggregation Induced Phosphorescence Based On Phenylsulfide Skeleton

Breakthrough innovations in light-emitting materials have opened new exciting avenues for science and technology over the last few decades.Aggregation-induced emission（AIE）represents one of such innovations.Aggregation-induced emission（AIE）is an abnormal phenomenon that some certain organic luminogens exhibit much enhanced emission from solution to aggregation.Attracted by the abnormal phenomenon of aggregation-induced luminescence（AIE）,scientists devoted great efforts to clarify the corresponding intrinsic mechanisms,which proposed many potential mechanisms,such as restricted intramolecular rotation（RIR）,J-aggregation,molecular planarization,and distortion intramolecular charge transfer（TICT）,etc.The tight packing in the aggregated state greatly enhances the luminescence of AIE molecular probes（instead of individual molecules）.Guest molecules can regulate the aggregation of AIE molecules through steric hindrance,coordination,hydrophobic,electrostatic interactions,especially through the effects of viscosity and polarity.Since the publication of the AIE phenomenon in 2001,AIE materials have attracted widespread attention from scientists due to bright solid-state light emission and a unique emission"turn-on"process.Compared with ACQ systems,the new AIE systems have multiple notable advantages,such as excellent stability,facile fabrication,high signal-to-noise ratio,and low detection limits.Widespread of attention to the AIE phenomenon and a better understanding of the mechanisms behind its effects have led to the discovery of many systems with these characteristics.The AIE material hardly emits light when dissolved in a solvent,and the aggregates formed after the poor solvent is added emit bright fluorescence.Organic luminogens that can emit intense luminescence in aggregation or solid state,are highly desirable for the development of many important areas,such as organic light emitting diode（OLEDs）,sensor,and bio-imaging.Therefore,aggregation-induced luminescence（AIE）has attracted worldwide attention for its unique optical phenomena and huge potential applications.Since then,aggregation-induced light-emitting molecules from blue to red and even near-infrared have been successively developed and successfully used in optical devices,chemical sensing,and biological imaging.In this thesis,we designed and synthesized two new light-emitting molecules hexa（3-hydroxy-1-phenylthio）benzene（HPB）and 2,3,5,6-tetrakis（4-hydroxy-phenylsulfanyl）terephthalonitrile（THPT）.Based on these molecules,we have further introduced the functional groups to construct a phosphorescent molecular probe,and used the aggregation of molecular probes to induce luminescence properties to achieve the detection of calcium ions and biological imaging.The following are the main contents of this study:（1）In biological systems,calcium ion is an extremely important signal ion,so the detection and imaging of calcium ion becomes extremely important.In organic solvents,hexa（3-hydroxy-1-phenylthio）benzene（HPB）was prepared through nucleophilic substitution reactions between hexafluorobenzene and4-hydrobenzenethiol.The obstained phosphorescent molecule does not emit light in the solution state but emits yellow light in the aggregated state..The carboxylic acid groups were introduced into the HPB molecule to make it very water-soluble.A novel phosphorescent molecular probe for the specific detection of calcium ions was successfully synthesized based on its unique luminescence characteristics.The introduction of six carboxyl groups in the hexa（4-hydroxy-1-phenylthio）benzene（HPB）molecule not only significantly improves its water solubility,but also enables specific complexation of calcium ions.Through the aggregation-induced emission（AIE）effect of the synthesized probe{4-[penta（4-ethoxycarbonylm ethoxy phenylthio）phenylthio]phenoxy}butyric acid molecule,the recognition of calcium ions was achieved,and the molecule can produce bright yellow phosphorescence in the presence of calcium ions.The research on the related mechanism shows that the unique molecular structure makes the constructed probe highly selective for calcium ions.Our results show that the developed calcium ion luminescence sensor can not only quantify calcium ions,but also be used for biological imaging.（2）Red-emitting materials are promising fluorescence probes in biology due to their large penetration depth,faint background autofluorescence and trivial irradiation harm to cells.Based on the red light-emitting AIE material has high photobleaching resistance,low toxicity and high efficiency emission,the design and preparation of red light-emitting AIE material for calcium ion detection has become very important.Theluminescentmolecule2,3,5,6-tetrakis（4-hydroxy phenylsulfanyl）terephthalonitrile（THPT）with aggregation-induced phosphorescence was prepared by nucleophilic substitution reactions in an organic solvent.Four carboxylic acid groups were introduced into the THPT molecule,and a new type of red phosphorescent molecular probe for calcium-specific detection was designed and synthesized.The introduction of four carboxyl groups in the THPT molecule not only significantly improves its water solubility,but also enables specific complexation of calcium ions.Through the aggregation-induced emission（AIE）effect of the synthesized probe（THPT-4CH₂COOH）,the recognition of calcium ions was achieved,and the molecule can produce bright red phosphorescence.The excellent imaging performance of calcium ions in Arabidopsis indicates that the probe has excellent calcium imaging performance and greater application prospects in living cells.In summary,based on the characteristics of aggregation-induced phosphorescence molecules,we have designed and synthesized two new types of luminescent molecules with significant aggregation-induced phosphorescence properties.By modifying two novel light-emitting molecules with the functional groups,yellow and red light-emitting molecular probes for specific detection of calcium ions were obtained.Taking plant Arabidopsis thaliana as an example,the imaging performance of the probe on calcium ions in living cells was further evaluated.