Tetraphenylethene-based Tetracationic Dicyclophanes And Their Fluorescence Properties

In the past years,supramolecular chemists have developed many macrocycles,for example,cyclodextrin,cucurbituril,columnar aromatic hydrocarbon,asarone,calixarene,resorcinol,etc.At the same time,a series of pyridine cationic macrocycles represented by"bluebox"have been developed rapidly.These cationic macrocycles are used in host-guest recognition,fluorescence recognition and cell imaging,molecular machines and so on.However,these cationic macrocyclic molecules mainly focus on their structure,host-guest recognition and other properties,the examples of fluorescent cationic macrocycles are still very limited.Tetrastyrene is a typical aggregation induced emission(AIE)molecule,which is easy to synthesize and has high quantum yield in solid state or aggregation state.Therefore,introducing tetrastyrene as a fluorophore into cationic macrocycle can make cationic macrocycle have more excellent optical properties.In this theise,five tetraphenylethene-based tetracationic dicyclophanes 1-5 were synthesized,1 can self-assemble into crystalline nanospheres in an aqueous solution,and has excellent AIE properties(?_F=97.7%).The assembled crystal nanospheres can achieve high antenna effect(14.3)and energy transfer efficiency(FRET)(?_ET=77.5%)in water environment by loading with organic dyes(such as Nile red).As fluorescent nanomaterials,the AIE and light harvesting supramolecular systems have potential applications in tumor cell imaging,tumor diagnosis and photodynamic therapy.Based on 1,four functional dicyclophanes molecules 2-5 with different substituents(such as NO₂,Br,OCH₃,OH)were designed and synthesized.Due to the introduction of different substituents,their optical properties are different.Dicyclophanes molecules can self-assemble into nanospheres in an aqueous solution.These nanospheres,as a single-molecule-based supramolecular platform,can combine with ATP through electrostatic interaction,and realize the selective detection of ATP in aqueous solution by fluorescence quenching/enhancement.Therefore,this water-compatible supramolecular system with AIE property can be developed to a simple approach for the detection of biological molecules in biocompatible media.