Study On The Fluorescence Discoloration Properties Of Triphenylamine-substituted Acylhydrazone Derivative

In recent years,organic light-emitting small molecule materials have attracted people's attention due to their simple synthesis,cheap raw materials,high yield,and their wide application in sensors and safe storage.The physical or chemical properties of these materials can undergo obvious changes under external stimulis,which are easy to observe and provide great convenience for human life.Therefore,studying new materials with specific properties in response to a variety of external stimulis is the focus of scientific research.In this paper,two acylhydrazone derivatives based on triphenylamine groups were designed and synthesized,and their multi-stimuli-responsive behavior were studied.1.We designed and synthesized 4-(4-(dodecyloxy))phenyl-4-trianiline hydrazine(TBHM).TBHM showed intramolecular charge transfer(ICT),and exhibited iron ion,force and acid responsive properties.The results of UV-Vis absorption spectra and fluorescence spectra proved that TBHM had good intramolecular charge transfer.TBHM showed high sensitivity and selectivity to Fe³⁺.It could be seen from the UV-Vis absorption spectra,fluorescence spectra and the mass spectrum that TBHM formed a 1:1 complex with Fe³⁺,which blocked the intramolecular charge transfer and lead to fluorescence quenching.2.TBHM exhibited mechanofluorochromism.After grinding,the color changed from blue to cyan,and can be restored by heating.This may be due to the molecular conformational change,i.e.,TBHM rotated to a more coplanar position upon external force,leading to the extension of?-conjugation and subsequent planar intramolecular charge transfer(PICT).At the same time,the morphology and aggregated structure have changed,suggesting its less ordered structure.In addition,the TBHM organogel and xerogel also exhibited reversible and remarkable fluorescence on/off properties to TFA/TEA.The ¹H NMR,the absorption spectra and the theory of frontier molecular orbits indicated that the protonation of TBHM with TFA.3.We designed and synthesized 4-dimethylaminophenyl-4-triphenylamino hydrazine(TBQM).The results of UV-Vis absorption spectra and fluorescence spectra proved that TBQM had good intramolecular charge transfer(ICT).TBQM exhibited mechanofluorochromism.After slightly grinding,the molecule changed from blue to cyan,and after hard grinding,it became yellow-green,as well as the fluorescence intensity changed from weak to strong to weak.After CH₂Cl₂fumigation,the fluorescence color recovered.The TBQM molecule contained a twisted triphenylamine unit,whose benzene rings were connected to each other by a single rotatable bond.In the pristine solid,the intermolecular?-?interaction may be inhibited by the strong lateral intermolecular hydrogen bonding interaction,resulting in a non-radiative transition,so the luminescence of the pristine solid is relatively weak.Under slightly grinding,the intermolecular hydrogen bonding interactions of some molecules weakened slightly and the?-?interactions increased slightly,the energy loss was reduced through non-radiative rotation relaxation,thereby improving the photoluminescence efficiency.When the grinding increased,the intermolecular hydrogen bonding weakened obviously,the?-?interactions were obviously enhanced,and the molecule packed tightly,quenching the excited state to some extent.Moreover,the molecule changed from crystalline state to amorphous state after hard grinding.In addition,TBQM exhibited acidofluorochromism.After TFA fumigation,the blue emitting color underwent cyan,green,and yellow,and finally the fluorescence was quenched.Upon TEA fumigation,the fluorescence recovered.The¹H NMR,absorption spectra and the theory of frontier molecular orbits indicated that the molecule underwent two protonation processes.