Synthesis Aryl Ethylene Derivatives And Study Of Their Stimulating Response Behavior To Mechanical Force,Acid And Light

Stimuli-responsive materials are a class of "smart" materials that cause physical or chemical changes in materials under the influence of external stimuli(mechanical forces,light,acids/bases,ions,ultrasound,etc.).Such materials have a wide range of potential applications in sensors,security inks,medical facilities,intelligent robots,and memory chips.Therefore,more and more stimuli-response smart materials have been rapidly developed in recent years.Among them,organic fluorescent molecules,as a member of the stimuli-response material,have the advantages of clear structure,easy modification,flexible large-area preparation,and easy physical or chemical changes under external stimulation,which are increasingly favored by researchers.So the organic conjugated molecules in this paper are the research objects.Based on the D-?-A non-planar skeleton,the molecules of luminescent properties and mechanofluorochromic properties and acidfluorochromic properties are studied by changing the donor and acceptor groups of the molecule.And the light-responsive properties,on the basis of which we prepared a high-contrast mechanofluorochromic and acidfluorochromic material.And on the basis of naphthalene,changing the coupling position achieves a smart material with significant optomechanical response.Some creative results have been obtained,and outline below:(1)Two benzothiazole derivatives with triphenylamine(CBVD)and phenothiazine(CBVP)moieties as electron donor groups were prepared,and their solid luminescence and mechanofluorochromism(MFC)were investigated and compared.Solvent-dependent fluorescence spectra and quantum chemical calculation indicate that the luminescence of both compounds originates from the intramolecular charge transfer transition.Although the two compounds have similar absorption spectra in solution,CBVP possesses red-shifted fluorescence as compared with CBVD.Similar to that in solution,CBVP in crystal state has longer emission wavelength than CBVD in crystal state.Crystal structures indicate that their molecular stacking models in crystal phases are different.J-aggregate and H-aggregate coexist in CBVD crystal,whereas only H-aggregate was observed in CBVP crystal.Moreover,CBVP exhibits reversible luminescence color change from yellow to orange-red with a spectral shift of 36 nm under mechanical force stimuli,whereas CBVD has a spectral shift of only 20 nm,indicating poor color contrast.UV–Vis absorption spectra show that the mechanical force induces the disappearance of H-aggregate in CBVD crystal and leads to stacking model transition from H-aggregation to J-aggregation in the CBVP system.(2)New D-?-A type quinoline derivatives(CbzVQ and TPAVQ)were synthesized via Knoevenagel condensation reactions.They exhibited reversible high-contrast mechanofluorochromic(MFC)behavior under grinding/fuming treatment.Taking CbzVQ as an example,its fluorescence could be switched from blue to greyish green by grinding the as-synthesized sample into ground powders,and the fluorescence emission was red-shifted from 449 nm(with shoulders at 475 nm and 520 nm)to 578 nm(with shoulders at ca.450 nm and 500 nm).Such large shift of the maximal emission peak during MFC processes was rare reported.In addition,the casting films of CbzVQ and TPAVQ emitted blue and green light,respectively,which was turned to red rapidly induced by TFA(trifluoroacetic acid)vapor.Moreover,the emission could be recovered stimulated by TEA(triethylamine)vapor,so the quinoline derivatives exhibited reversible fluorescent sensory properties.TPAVQ showed better performance in the detection of TFA vapor than CbzVQ due to the strong electron-donating ability of triphenylamine compared with carbazole.The detection limit and the decay time of TPAVQ towards TFA vapor were 163 ppb and 0.22 s,respectively.Apparently,the D-?-A type quinoline derivatives are candidates as multi-stimuli responsive fluorescent materials.(3)The naphthalenylacrylic acids(N1AA and N2AA)and naphthaleylacrylamides(N1AAM and N2AAM)have been synthesized.Interestingly,there were two crystal types separated for N1 AA.The monoclinic N1AA-G(C,Z = 8)emits blue fluorescence and cannot take place [2+2] cycloaddition.However,blue-green monoclinic N1AA-G(P(?),Z = 4)polymer can react under the illumination of the UV lamp(? = 365 nm).When exposed to spatially uniform light irradiation,these photoreactive plate-like crystals of N1AA-G bend and jump.After the light is turned off,Their shape were kept.In addition,since N2 AA also satisfies the conditions of the [2+2] photocyclization reaction,the plate-like crystals of N2 AA also exhibit a jumping away from a UV light source.The compound N2 AA features a basic face-to-face stacking,while N1AA-G was a wavelike type stack.Therefore,the photomechanical behavior of N2 AA was more pronounced than N1AA-G.