Multi-stimuli-responsive Fluorescent Properties Of Anthracene-substituted Acylhydrazone Derivative

Organic light-emitting materials are widely used in mechanical sensors,security paper and optical storage due to their higher fluorescence quantum efficiency and easy modification.With the further development of scientific research,multi-stimuli-responsive luminescent materials have attracted more attention due to their tunable structures and controllable functions.These luminescent materials can respond to a variety of external stimuli such as mechanical forces,light,acids/bases,ultrasound,anions,cations and electromagnetic fields,then exhibit changes in phase and colors.But until now,such materials are still limited,so the works in stimuli-responsive luminescent materials will be an innovative and need to be developed.This dissertation focuses on the anthracene-substituted acylhydrazone derivative AHP-T8 with multi-stimuli-responsive properties.1.The AHP-T8 could form a stable gel in cyclohexane.The enhanced fluorescence emission had been observed during gelation although the dilute solution of AHP-T8 was almost non-fluorescent.The strong fluorescence in the gel phase of AHP-T8 might be attributed to the following reasons:1)The intermolecular hydrogen bonds would probably favor excimer formation and reduce the bond rotation within AHP-T8 to prohibit the nonradiative transitions to some extent;2)The compound AHP-T8 formed J-aggregations in the organogel.In addition,AHP-T8 showed an unusual aggregation induced emission(AIE)property in THF-water solutions.Maybe due to the formation of different aggregates,AHP-T8showed the emission color changes from blue to green with the increase of water.2.The AHP-T8 organogel and xerogel showed visible light responsive behaviors.When the organogel was exposed under visible light,the gel-sol phase transition occurred,and the corresponding morphology,fluorescence intensity,intermolecular hydrogen bonding and the structure all changed.In addition,the xerogel was more sensitive to visible light than that of organogel.The photoresponsive behaviour of AHP-T8 upon irradiation by visible light was demonstrated to be due to the E-Z isomerizations of-C=N-group,rather than the photodimerization of anthracene groups.3.The emission of AHP-T8 could be reversibly tuned by mechanical force.The experiments revealed that the mechanical force weakened the intermolecular hydrogen bonding and promoted the increase ofπ-πoverlap between anthracene of the AHP-T8 molecules,the transformation between the xerogel with crystalline features and amorphous states was responsible for the mechanofluorochromism behavior.In addition,the reversible switching of the emission colors could be achieved by grinding,annealing or fumigation with dichloromethane(DCM).4.It was found that AHP-T8 exhibited remarkable and reversible acid/base stimulated fluorescence switching properties in organogel,solution and solid state.The UV-vis absorption spectra,~1H NMR experiments and theoretical calculations couldconfirmthatthisswitchablephenomenonattributedtothe protonation/deprotonation of AHP-T8 by fumigation of TFA and TEA.During the instillation of TFA into the AHP-T8 gel,the protonation effect caused the dramatic phase transition from gel to solution with the colors change and the on/off switching fluorescence.The AHP-T8 films with alternate fumigation of TFA/TEA vapors exhibited their luminescence switching between green and orange yellow.