Multistimuli-responsive Properties Based On Pyrene- And Anthracene-substituted Acylhydrazone Derivatives

Organic smart materials show dynamic and reversible fluorescence transformation.Some organic fluorescent materials usually have a strong fluorescence in the dilute solution,but the fluorescence is often quenched in the concentrated solution or solid state,which limits the performance in optical devices.Therefore,the organic light-emitting materials with aggregation-induced emission(AIE)have attracted a lot of attentions from scientists.Combined with our previous work,in this article,we synthesized two types of acylhydrazone derivatives containing imide group(C=N)and the chromophore(anthracene group and pyrene group),and studied the gelation ability,AIE properties,multistimuli-responsive properties.The main contents are as follows:1.4-(3,4-dioctyloxy)phenyl-1-pyrene acylhydrazone(PAH-8)was synthesized.PAH-8 could form a yellowy organogel in DMSO with the critical gel concentration(CGC)of 1.25 mg/m L.The organogel was thermally reversible and stable at room temperature.The PAH-8 organogels exhibited photo-responsive behaviors due to the trans-cis isomerizations of C=N bond upon exposure to visible or UV light.The trans-cis isomerizations of C=N bond of PAH-8 was more sensitive to the visible light than the UV light.2.The PAH-8 showed unusual aggregation-induced emission(AIE)and mechanofluorochromism.PAH-8 could form different aggregates in tetrahydrofuran(THF)-water mixtures with different water fraction,the formation of different aggregates caused obvious fluorescence changes.the luminescence color of PAH-8 ground xerogel changed from blue to green.The fluorescence changes originated from pyrenyl excimer from E1(partially overlapping)to E2(completely overlapping)after grinding.The PAH-8 precipitate from THF also displayed mechano-fluorochromic behavior similar to xerogel.Whereas the drop cast sample of hot solution of PAH-8 in THF did not exhibit mechanofluorochromism,indicating that the fluorescent properties of PAH-8 can be tuned by different preparing conditions.3.The 9,10-bis(4-(3,4-dioctyloxy)phenyl)-anthracene acylhydrazone was synthesized,AHBP-8 could form a stable gel in THF and chlorobenzene with gelation-induced enhanced fluorescence emission.AHBP-8 had a unique aggregation-induced emission in tetrahydrofuran(THF)-water mixtures with different water fraction,and the results of fluorescence,UV-visible absorption spectra and SEM explores the relationship between the fluorescence properties and aggregate morphology.AHBP-8 xerogel from chlorobenzene showed obviously mechano-fluorochromic behaviour,the emission color turning from yellowish green to orange emission after grinding,and the orange emission could be returned to green emission by annealing and fuming.The results of FTIR、SEM and XRD confirmed that the intermolecular hydrogen bonds were significantly weakened after grinding and the ordered alignment was destroyed.So the observed mechanofluorochromism was attributed to the results of crystalline-amorphous phase transition.