Study On Luminescence Properties Of Smart Response Materials Based On Acylhydrazone Group

Stimuli-responsive organic luminescent materials have gained considerable attention from researchers and engineers because of their unique properties and potential applications in organic light-emitting diodes?OLEDs?,bio-imaging,solar cells,sensors,and so on.These smart organic luminescent materials can change their physical or chemical properties upon exposure to a particular stimulus,such as heat,forces,light,acids/bases,solvent,anions,cations etc.Therefore,it is a current research hot spot to exploit the new stimuli-responsive materials,and in-depth study and understand the structure-property relationships as well as the mechanisms,in order to further design and develop materials with intriguing properties.The thesis focuses on luminescence properties of smart response materials based on acylhydrazone group.1.Two types of new anthracene-based acylhydrazone derivatives?AHBP-1 and AHP-1?have been designed and synthesized.The aggregation-induced emission?AIE?of AHBP-1 and AHP-1 were studied.Besides,the compounds AHBP-1 and AHP-1 manifest significant the mechanofluorochromism?MFC?properties.However,the fluorescent emission wavelength of AHBP-1 before and after grinding shows larger red-shift compared with that of AHP-1.But the fluorescence emission intensity of AHBP-1 is lower than that of AHP-1,which may be due to an increase in the number of acylhydrazone branch in the AHBP-1,resulting in an increase in the degree of molecular conjugation and an increase in the intermolecular interaction force.In addition,the mechanism of MFC behavior may be due to the transition of the aggregate structure from order to disorder phase transition.2.We designed and synthesized thiophene substituted anthracene acylhydrazone derivative the 2-thiophene-9-anthracene-acylhydrazone?ASD?.ASD grew into two single crystals in DMF solution:cis ASD-Z and trans ASD-E.The result of single crystal X-ray analysis show that the crystal ASD-Z is a tetragonal system,the molecular conformation is highly distorted,a strong intermolecular hydrogen bond interaction is formed between DMF solvent molecules and ASD-Z,while the intermolecular interaction of ASD-Z is weak,and the stacking mode is loose,but the structure is stable.The crystal ASD-E is a monoclinic system,an almost planar structure,the stacking mode is close,and there are strong intermolecular hydrogen bondings and?-?interactions between molecules,thus causing fluorescence quenched.At the same time,ASD precipitated sample from chloroform solution?ASD-CHCl₃?emitted a green fluorescence and the precipitated sample from tetrahydrofuran solution?ASD-THF?was non-fluorescent.However,the ASD-THF exhibited an on-off fluorescence phenomenon of mechanofluorochromism behavior and photo-response behaviors.After the ASD-THF powder is ground,the emission changes from non-fluorescence to yellow-green fluorescence,and the reversible conversion of the fluorescence emission color can be achieved under annealing.The FT-IR and XRD results confirmed that the intermolecular hydrogen bonding interaction of the sample after grinding was weakened,and the aggregate changed from crystalline to amorphous,and the order of ASD-THF powder was destroyed.After visible light irradiation,maybe due to the trans-cis isomerization occuring in ASD-THF molecules,and the intermolecular interaction,morphology and aggregate structure changing significantly,the emission changes from non-fluorescence to yellow-green color,and the fluorescent intensity sharply increases and then decreases.3.We designed and synthesized thiophene substituted pyrene acylhydrazone derivative the 2-thiophene-1-pyraniazide?PSD?.The PSD exhibits three distinct fluorescence switching behaviors to external stimulus.First,The PSD could exhibit fluorescence color conversion from blue to green as the unusual AIE property.The PSD could form different aggregates in tetrahydrofuran?THF?-water mixtures with different water fraction,the formation of different aggregates caused obvious fluorescence changes.Secondly,the PSD exhibited reversible MFC with the emission colors changing from blue-green to yellow-green upon grinding.The MFC properties might be attributed to changes of the intermolecular interactions and structural transition from crystalline structure to amorphous phase.Third,The PSD exhibited remarkable fluorescence quenching and naked-eye visible color changes in the presence of F^-and Fe³⁺in DMSO dilute solution,respectively.Upon addition of F^-,the results of absorption and ¹H NMR experiments could confirm that the extended conjugated system formed through the deprotonation reaction of amide?-NH?group.In addition,Fe³⁺responsive mechanism was attributed to the formation of the complex of PSD and Fe³⁺with 1:1 ratio,destroying the conjugation effect,thus the absorption spectrum is blue-shifted and the fluorescence quenched.