Tetrastyrene-based Aggregation-induced Fluorescent Probe For Detecting F^- Ions And Zn²⁺ Ions

Reaction-based fluorescence probes irreversibly react with certain molecules or ions by forming or cleaving co-valent bonds to specifically recognize the target analytes,featuring high sensitivity and good selectivity.Among reaction-based fluorescent probes,the reaction-based aggregation induced emission?AIE?fluorescence probes have been attracted more attention since they can overcome the aggregation induced quenching?ACQ?effect encountered in the traditional fluorescence probes.Our group has developed several catalytic chromogenic reactions or catalytic fluorogenic reactions by employing TMB or OPD as the substrate.Therefore,it could be further considered that,whether tetraphenylethylene?TPE?based on AIE effect can be chemically modified to synthesize their derivatives or not,and could their derivatives further employed in chromogenic reactions or fluorogenic reactions,and thus could novel reaction-based chemosensing systems successfully established?Based on these considerations,in this paper the following two aspects have been carried out:?1?By employing the two-step synthesis method to prepare TPEOH featured by the AIE effect as the skeleton,two novel TPE-based fluorescence probes TPEONO₂ and TPEO?NO₂?₂,bearing a p-nitrobenzenesulfonyl and 2,4-dinitrobenzenesulfonyl,respectively,were further synthesized.Due to the strong electron-withdrawing effect of-NO₂ group on the benzene rings and the strong intermolecular?...?stacking interaction between two benzene rings containing-NO₂ group,the two synthesized probes are non-fluorescent both in their dissolved and aggregated state.It was found that,introducing a certain amount of F^-ions could break the sulfonyl ester bond?S-O bond?of the probes to release TPEOH which could induce strong emission by its aggregation state.Yet,other related anions couldn't trigger such fluorescence change.Thereby,novel fluorescence sensing systems with a“turn on”mode could be successfully established with limits of detection of 0.064?M and 1.27?M,respectively.Compared with the fluorescence response of TPEONO₂ probe bearing one-NO₂group towards F^-ions,TPEO?NO₂?₂ probe bearing two-NO₂ groups showed worse fluorescent response,likely considering that the steric hindrance of ortho-NO₂ group of benzene ring results in F^-ions could not effectively attack S-O bond.?2?On the basis of the above mentioned findings,an AIE-based fluorescence probe TPEOCHO,bearing a-CHO group and o-OH group,was further designed and synthesized.It was found that,by employing the condensation reaction between the-CHO group on TPEOCHO and the-NH₂ group on ethylenediamine,a TPEOCHO derivative containing an imine bond?-CH=N-?could be in situ formed.Correspondingly,the color of the reaction solution immediately changed from colorless to pale yellow.Due to the coordination interaction between Zn²⁺ions and the new formed imine compound,the fluorescence intensity was found to be enhanced and the fluorescence peak blue-shifted ca.60 nm.Thus,a novel Zn²⁺ions fluorescence sensing system could be established.