Stimulus Response Fluorescent Switching Properties Of Anthracene-substituted Acylhydrazone Derivatives

Stimulus-responsive organic light-emitting materials are favored by researchers for their sensitive response to different types of external stimuli(force,light,solvent,p H,ions,etc.).At present,they are widely used in mechanical sensors,data storage equipment,fluorescent probe,photoelectric equipment and so on.Although the properties of stimulus-responsive materials depend largely on the properties of their molecular structure,the arrangements and stacking structures also affect the properties of the materials to a great extent.Therefore,designing novel materials to explore the relationship between the molecular of stacking structures and properties has always been a hot research field for researchers.However,there are few reported acidochromic fluorescence materials with two protonation binding sites.In order to obtain multiple fluorescence conversion materials,we introducted two protonation binding sites to synthesize dimethylamino-substituted anthracylhydrazone derivative AHY,so as to further explore the relationship between structure and properties.In addition,a systematic study of halogen effect on mechanofluorochromic material remains still rare,the mechanism of this effect is not well understood,and to explore the effect of different halogen substituents on the mechanically induced fluorescence behavior of hydrazone derivatives,we have designed and synthesized anthracylhydrazone derivatives FAH,CAH and BAH with fluorine,chlorine and bromine as terminal substituent.1.Adimethylamino-substitutedanthracylhydrazonederivative,4-dimethylaminoaniline-9-anthracylhydrazone(AHY),has been synthesized,which exhibits significant mechanofluorochromic and acidochromic properties.Upon mechanical grinding,the emitting color of AHY samples changed from bright green to yellow,accompanied by a significant red-shift of the fluorescence emission peak.After annealing treatment,the fluorescence of AHY samples returned to the initial state.Combined with the experimental results of UV-Vis absorption spectra and IR,the reason of fluorescence changes may be that the grinding force weakened the intermolecular hydrogen bond,increased the overlap degree of anthracene plane between adjacent molecules,and led to the enhancement of?-?interaction.Moreover,AHY has obvious acid responsive behavior in the solid film and the solution.When the AHY film was exposed to trifluoroacetic acid(TFA)saturated vapor,the fluorescence of the AHY film was quenched and its color changed from yellow to orange under natural light.The results of UV-Vis absorption spectra and ¹H NMR experiments confirmed that the acidochromic fluorescence change attributed to the protonation of AHY.At room temperature,the sample after acid fumigation can spontaneously return to the original state in 40s.In addition,when trifluoroacetic acid was added to AHY solution,the protonation reaction resulted in a significant change in UV-Vis absorption spectrum of the solution.2.AHY film shows interesting photo-responsive behavior.Under photo-irradiation,the original green fluorescence of AHY film gradually disappeared and the fluorescence intensity decreased.Meanwhile,FT-IR and SEM experiments showed that the intermolecular hydrogen bonds and morphology of aggregates changed significantly of AHY film after photo-irradiation.In the ¹H NMR experiment,many proton peaks were split after photo-irradiation,and the cis-configuration proton peaks appeared in the high field.The experimental results proved that the photo-responsive mechanism of AHY may be due to the trans-cis isomerization of-C=N-by photo-irradiation.At the same time,AHY film can show obvious photopatterning.3.Anthracylhydrazone derivatives FAH,CAH and BAH with different halogens as substituent groups were synthesized.All three compounds exhibit significant mechanofluorochromism,which is due to the change of aggregate structure from ordered to disordered.A series of experimental results show that different halogen substituents have no significant effect on the mechanofluorochromic properties of anthracylhydrazone derivatives.In addition,BAH dilute solution is sensitive to F^-and Fe³⁺.When excess F^-was dropped into BAH dilute solution,resulting in fluorescence quenching of the BAH solution.¹H NMR experiment proved that the reaction between BAH and F^-was due to the deprotonation of N-H group.In addition,when Fe³⁺was added to BAH dilute solution,the fluorescence quenched and the absorption spectrum blue shifted at the same time,which was probably that BAH and Fe³⁺formed a complex with a ratio of1:1,which destroyed the conjugate effect.