Ionic AEE Red Light Material Modified By Pyridinium Salt

Molecules/polymers characterized by aggregation-induced emission(AIE)or aggregation-enhanced emission(AEE)with red-emission have gained much attention in research fields such as chemo-/bio-sensors and cell/tissue imaging.Either anionic or cationic moieties bestow fluorophore with outstanding advantages.The net charges,on the one hand,help the aromatic luminogens to acquire hydrophilicity or dissolve in aqueous media,and on the other hand lead to the formation of electrostatic complexes with oppositely charged species in aqueous media,thus the oppositely charged species can be fluorescently detected.Ionic luminogens generally show more stable luminescence behaviors by virtue of the electrostatic interaction,which protects them from large changes in molecular packing caused by various stimuluses during the application process.In addition,AIE/AEE probes with red-emission own a higher signal-to-noise ratio and a deeper penetration in tissues.In the current situation,researches about ionic AIE/AEE small molecules have started to show effects.However,development of such kind of molecules&polymers needs particular enhancing.Vast majority of ionic AIE/AEE polymers were prepared through main-chain polymerization followed by post-modification.The whole process requires harsh conditions.Therefore,enriching the category of ionic AIE/AEE materials and developing efficient routes to polymers are of great significance.First,we prepared a three-branched cationic molecule from the quaternization reaction between 1,3,5-tribromomethylbenzene and mono-pyridinyl-modified tetraphenylethene.And then,we applied the same strategy,by using dual-pyridinyl modified tetraphenylethene and 1,3,5-tribromomethylbenzene as an A2+B3 system,to the synthesis of a cationic hyperbranched polymer.The above-mentioned small molecule and polymer both show AEE property and red-emission.The polymerization was efficient under mild conditions.The electrostatic interaction bestows the charged polymer with enhanced phase stability,thus it shows low susceptibility to external stimuli such as mechanical grinding in solid,solvent polarity in solution,and pH change in aqueous medium.This cationic red-emitting polymer also has good membrane permeability,and the results of living cell stain experiments suggest that it may find applications as a stable fluorescent probe for bioimaging.