Synthesis And Application Of Red Triphenylamine-Bodipy Fluorescent Probe For Hypochlorite

As a kind of important reactive oxygen species,hypochlorous acid plays an important role in the organism.When hypochlorous acid overdoses in the organism,it will lead to abnormal oxidation of intracellular biological molecules,resulting in various disease and tissue damage.Therefore,it is important to achieve rapid,sensitive,and highly selective detection of hypochlorous acid in living organisms.Based on the structure of triphenylamine-BODIPY with the excellent properties,an important aspect of this work has been carried out.To the detection of hypochlorous acid as the goal,two hypochlorous acid probes was developed using the oxidative cleavage of C=N or C=C double bond.First,a pyridyl triphenylamine-BODIPY structure PPA-BODIPY was built through the palladium-catalyzed Heck reaction.And then the final product OX-PPA-BODIPY was obtained through the formylation reaction at the 2-position of BODIPY and Schiff reaction.The compounds were confirmed by magnetic resonance(1H NMR and 13C NMR)and high resolution mass spectrometry(HRMS-MALDITOF).The fluorescence of the probe is quenched due to the isomerization of C=N and the fluorescence quantum yield is 0.02.When reacted with hypochlorous acid,the oxime is oxidized to an aldehyde group accompanied by the fluorescence quantum yield is 0.43.OX-PPA-BODIPY displayed a color change from pink to green and a remarkable "turn on"fluorescence response towards ClO-,realizing a naked eye visualization.The pure dye was applied to cell imaging and showed a better uptake by A-549 cells which suggested its promising application for biosensors.A conjugated molecule BCPA-BODIPY-TCF with D-?-A structure was designed and synthesized by introducing tricyanofuran group into the fluorescent precursor of(3,6-di-tert-butylcarbazol-9-yl)triphenylamine-BODIPY(BCPA-BODIPY).The purity of the resultant products and intermediates has been confirmed by 1H NMR and 13C NMR.BCPA-BODIPY is orange powder and has a sharp peak at 495 nm,full width at half maximum(FWHM)of which was 1.06×103 cm-1.The presence of tricyanofuran group in the probe compared with BCPA-BODIPY gave rise to 85 nm red-shifted absorption spectrum,which was due to a strong intramolecular charge transfer(ICT)transition in the D-?-A structures.The compound BCPA-BODIPY-TCF presented a remarkable change and a broad peak located at 580 nm,dispalying purple black in solid state.C=C double bond is the reaction site and broken under the oxidation of hypochlorous acid,accompanied by the removal of the acceptor tricyanofuran.The ICT effect is weakened,corresponding to a color change from orange to pink,which was clearly visible to the naked eyes.Other reactive oxygen species and anions caused no obvious phenomenon,the detection limit of 1.78 × 10-7 M.According to the rapid naked eye recognition of hypochlorous acid,thel probe was made into the test strip,which can be used quickly and easily for the visual inspection of hypochlorous acid in the environment.Because of the excellent photophysical properties of Aggregation induced emission(AIE)materials,they have recently generated great interest in the field of organic light-emitting diodes(OLEDs),biological cell imaging,fluorescent nanoparticles,fluorescent probes and so on.So another important aspect of this work is as following.A novel building block BODIPY-stilbene was constructed and a series of aggregation-induced fluorescence enhanced molecules were synthesized by modification of triphenylamine-BODIPY taking advantage of the AIE-active nature.And their photophysical properties and aggregation-induced fluorescence properties were studied in detail.The four fluorescent molecules MAPA-BODIPY,BODIPY-stilbene 1,2,3 were constructed by palladium-catalyzed Heck reaction with IPA-BODIPY as the key intermediates.All the final compounds were confirmed by basic structural characterization.Here,we constructed a new red AIEE building block with a D-?-A structure.The four fluorescent molecules show a bimodal structure in THF,and the maximum emission peaks are located at 603 nm,644 nm,652 nm and 644 nm,respectively.And these four fluorescent molecules exhibit aggregation-induced fluorescence enhancement(AIEE)properties.MAPA-BODIPY,BODIPY-stilbene 1,2,3 show red fluorescence in aggregated states,while BODIPY-stilbene 1 is the weakest.In addition,BODIPY-stilbene 1 with a carboxylic acid group can achieve selective identification of bovine serum albumin(BSA)based on its AIEE properties.Bovine serum albumin(BSA)was gradually added to the BODIPY-stilbene 1 solution,and the fluorescence emission intensity of the probe was significantly enhanced,showing a better BSA probe performance.And the probe has a good selectivity for BSA recognition.The Stern-Volmer plot demonstrated that the procedure of the fluorescence quenching induced by BODIPY-stilbene 1 was mainly a static quenching process.The apparent association constant value K and the binding sites value n are obtained from plots of log[(F0-F)/F]versus log[D].The apparent association constant value K of dyes is 4.43 × 107,indicating a high affinity for BSA.And the binding sites values n are calculated to be 1.84,respectively.