Mechanofluorochromic Properties Of Pyrene And Tetraphenylethylene Functionalized Acylhydrazone Derivatives

Mechanofluorochromic(MFC)materials are a kind of new materials whose fluorescence intensity or wavelength can be significantly changed under the external mechanical forces(grinding,stretching,impact,etc.).There are many factors influencing the performance of MFCmaterials.This article mainly introduced the influence of alkyl chain length,D-?-A structure,twisted conformation,and isomer effect and halogen substitution on the performance of force-induced fluorescence color change.The special optical properties of MFC materials make them have unpredictable prospects in the fields of pressure switches,rewritable photoelectric application materials and anti-counterfeiting inks And they have been attracted widespreadly.Therefore,the multifunctional mechanofluorochromic fluorescent materials have become Research hotspots of scientists in recent years.In this thesis,four pyrene-functionalized and five tetraphenylethylene-functionalized acylhydrazone derivatives were designed and synthesized,and their photophysical properties,acid/base stimulated fluorescence color change,and halogen substitution effect were studied respectively.The specific content is as follows.Chapter 1: We mainly summarized the development status and influencing factors of mechanofluorochromic fluorescent materials,and briefly introduced the luminescence properties of acylhydrazone derivatives and acid/base stimulated fluorescence color changes.Finally,the main research content and significance of this thesis are explained.Chapter 2: Four pyrene-based acylhydrazone derivatives PMBH?PMPH? PMNH and PMIH have been synthsised.These four molecules all exhibited aggregation-induced emission properties and reversible MFC properties.PMPH?PMNH and PMIH are isomers with pyridine groups.The acid/base stimulation of solid states and films of PMPH?PMNH and PMIH and it was found that PMPH?PMNH and PMIH were very sensitive to acid and base stimulation.In addition,the study also indicated that when the N element on the terminal is in the fourth position,the molecule has high-contrast MFC properties.Chapter 3: Two acylhydrazone derivatives TBBH and TBIH with tetraphenylethylene as the main body were synthesized,and the photophysical properties,aggregation-induced properties and multiple stimulation responses of TBBH and TBIH were studied.Powder X-ray diffraction(PXRD)and differential scanning calorimetry(DSC)studies have shown that the MFC properties of these two compoundswere caused by the phase change of the molecule from a crystalline state to an amorphous state.In addition,it was found that when the N element on the pyridine unit is at 4'-position,the molecule had higher contrast MFC properties.Chapter 4: Three halogen-substituted tetraphenylethylene-functionalized acylhydrazone derivatives TPEBH-F?TPEBH-C1 and TPEBH-Br have been designed and synthesized,and their photophysical and MFC properties were studied.It was found that the introduction of a halogen group at the 4'-position of the phenyl moiety resulted in a decreased red-shift in the concentration-dependent fluorescence emission.However,the molecule showed higher contrast MFC properties with the introduction of halogen atoms.