The Study Of Photodimerization,Thermochromism,and Application Of Sensor Imaging Based On BPEB And Its Ramifications

The central benzene ring of 1,4-bis[2-(4-pyridyl)ethenyl]-benzene(BPEB)molecule is connected to the para phase of the pyridine group by para-double bond,which has a unique symmetrical structure and contains multiple double bonds.2+2photodimerization can occur between molecules.Pyridine group is a Lewis base,can coordinate with a variety of metal ions,can also be hydrogen bond with hydroxyl,halogen atoms through halogen-nitrogen action to form crystals.BPEB molecule and its derivatives have attracted much attention because of their unique structural characteristics of double bond and pyridine group.They are widely used in complex,metal-organic framework,eutectics,molecular assembly and other fields.However,the current research on the stimulus response characteristics of BPEB derivatives and the relationship between structure and properties is not complete,and needs to be further improved.In this paper,BPEB and its derivatives as the research object,mainly explored the 2+2 ring addition process under the stimulation of ultraviolet light,after the structure modification brought by the thermochromic properties and its response mechanism with specific anions,effectively expanded the application space of BPEB.We prepared from BPEB molecules,and tried the dimerization reaction in DMSO.The BPEB was found to have two configurations trans-BPEB and cis-BPEB,both of which were prepared in the experiment,and their structures were characterized by nuclear magnetic hydrogen spectrum,mass spectrum,infrared spectrum,Raman spectrum,circular dichroism,ultraviolet spectrum and thermogravimetric analysis.Dimer-BPEB was synthesized in DMSO solution for the first time.The dimer-BPEB structure was characterized by NMR and 2D NOESY.The reaction does not require the use of template and catalyst,and the cycloaddition products of the two configurations are consistent.When trans-BPEB is added to the ring,the rotation of single bond between benzene ring and double bond occurs,which changes the configuration.From the 2D NOESY spectrum of trans-BPEB,we infer that an important reason for this reaction to occur is that the BPEB molecules in DMSO are arranged in a J aggregation manner.In the powder state,trans-BPEB does not react after being irradiated by 365 nm ultraviolet light,while cis-BPEB only changes its configuration.Since the molecule is in amorphous state under the powder state,neither of them has cycloaddition reaction.Only 365 nm with a power density of 0.35 m W/cm²is needed to drive the reaction.The reaction only responded to 365nm light,and the trans-BPEB was transformed into cis-BPEB under 473 nm light.Based on the 1,4-bis[2-(4-pyridyl)ethenyl]-benzene structure,we prepared three of its derivatives DC8,DC12,DC16,and study their color changing behavior under high temperature.The structures and properties of BPEB,DC8,DC12 and DC16 were characterized by nuclear magnetic hydrogen spectrum,mass spectrum,TGA,DSC,XRD,solid ultraviolet and solid fluorescence.The study shows that DC8,DC12 and DC16 all have the property of thermochromic,which are derived from the fact that heat makes the powder change from a microcrystalline state to an amorphous state,which is an irreversible phase change.The powder is recrystallized by adding ethanol to dry,and its fluorescence can be restored.Under the light of 365 nm,the phase transition temperature of DC8,DC12 and DC16 was 60?,far lower than the phase transition temperature they measured in DSC.This is because ultraviolet light can make the chemical bond rotate,365 nm ultraviolet light and heat both play a synergist,making their phase transition temperature lower.However,DC16 also has photochromic properties.DC16 and sodium sulfate had fluorescence response,and the fluorescence of the solution changed from green to orange.Subsequently,DC16 was combined with magnesium sulfate,sulfuric acid,potassium sulfate,and aluminum sulfate,and the solutions showed orange fluorescence at 365 nm.When the molar ratio of DC16 to sulfate ion is 1:1,the detection limit of sulfate ion is 3.3×10^-8mol/L.In this method,the fluorescence intensity was positively correlated with the concentration of DC16and sulfate ions.DC8 can be supramolecular assembled with cucurbunide[6](CB[6]).At 1.0×10^-6mol/L and lower concentrations,DC8 and other compounds and their assembly with CB[6]showed low toxicity to MCF-7.DC8,DC12 and DC16 can all enter MCF-7 to realize fluorescence imaging with low brightness.After the addition of CB[6],DC8@CB[6]and other molecules were sublamolecular assembled to form DC8@CB[6].DC8@CB[6]and other molecules were concentrated in the MCF-7mitochondria.DC8@CB[6],DC12@CB[6]and DC16@CB[6]were strongly correlated with the fluorescence position of LSO-tracker Red,and Pearson correlation coefficients were 0.814,0.698 and 0.432,respectively.After DC8@CB[6]and others enter the mitochondria,due to the hydrophobicity of DC8 and others,they form microcrystals and realize the fluorescence imaging of the mitochondria.DC8@CB[6]has potential value as a lysosomal dye.