Design,Synthesis And Performance Of Organic Luminescent Materials With Stimulus-response D-A Structure

Fluorescent and phosphorescent luminescent materials with organic donor-acceptor structure have broad application prospects in the fields of information storage,anti-counterfeiting,sensors,biomedicine.Stimulus-responsive organic light-emitting materials refer to functional materials whose light-emitting properties change under the action of electrical,mechanical stimulation,light,heat,pH,etc.At present,fluorescent materials with stimulus-response are more common,but multifunctional fluorescent materials are more common.Room temperature phosphorescent materials that are rarely reported and have multiple stimulus responsiveness are also rare.This thesis designs different electron donors and electron acceptors,introduces different substituents,adjusts charge transfer,luminescence effects,molecular stacking methods,and obtains fluorescence and room temperature phosphorescence luminescence with multifunctional,force-induced color change and acid-induced color change stimulation response material.In the second chapter of this thesis,we design a new dibenzo[a,c]phenazine-phenothiazine dyad(BNPTZ)bridged by a C-N single bond,which realizes AIEE,polymorphism,mechanochromsim,and high sensitivity to hydrostatic pressure,due to the twisted D-A structure.BNPTZ exhibits AIEE activity in THF/H20 system,owing to aggregation-inhibited non-radiative relaxation channels of the excited states.Fortunately,two types of single crystals of BNPTZ with distinctive luminescence were cultivated and the effect of different conformation and complicated intermolecular interactions on the luminescent property was analyzed.BNPTZ demonstrates responses to both shearing force and hydrostatic pressure.Interestingly,two different crystalline phases are involved in the color-changing process upon shearing and fuming.Upon shearing,the crystal powder suffers the luminescence color change from orange-yellow(565 nm)to redness(604 nm),because of the phase transition from OY-phase to amorphous triggered by an external force.When fuming,the amorphous phase would recover to YG-phase unexpectedly.When subjecting two single crystals to hydrostatic pressure,the OY-phase single-crystal underwent a clear color switch from yellow to orange and eventually to red.The YG-phase displayed a different color alteration from yellow-green to orange and further to red.Both of the two single crystals exhibited relatively high sensitivity to pressure with a wide spectral shift over 100 nm.Up to now,BNPTZ is a rare dyad that achieves polymorphs with high sensitivity to pressure.In the third chapter of the thesis,we designed carbazole as the electron donor and connected different pyrimidine derivatives to obtain a series of ultra-long room temperature phosphorescent molecules.The three compounds,CNCMCz,BPMCz,and CPMCz,all have more than 100ms after UV light is removed.Both CNPMCz and CPMCz exhibit purple fluorescence in the pristine state,and the light source is removed after excitation to have long-life yellow room-temperature phosphorescence.In the pristine state,BPMCz is blue fluorescence and room temperature phosphorescence is also yellow.Single crystal structure analysis showed that close molecular packing and intermolecular forces are the main reasons for the ultra-long room temperature phosphorescence of BPMCz and CPMCz.Secondly,CPMCz is also due to the introduction of methyl groups.Besides,CNCMCz has dual emission mechanochromsim,that is,under pressure stimulation,the fluorescence changes from the initial purple to blue luminescence,and the phosphorescence disappears.Through XRD data analysis,it can be seen that after CNCPMCz is ground,the order phase of the crystal increase and the crystal form may change.However,since it has not obtained a single crystal,its room temperature phosphorescence mechanism needs to be further explored.In the fourth chapter of the thesis,we designed to replace the electron donor with aminopyridine and connect the electron acceptor 4-bromophthalic anhydride to synthesize two compounds,Dpa-Pr-F and Dpa-Pr.The molecule Dpa-Pr has only fluorescence emission,which is yellow fluorescence and no phosphorescence.Dpa-Pr-F is green fluorescent in the initial state,yellow phosphorescent emission after the ultraviolet lamp is removed,phosphorescence lifetime t=26ms.After Dpa-Pr-F and Dpa-Pr are fumigated with trifluoroacetic acid,Dpa-Pr shows a blue shift of fluorescence and transforms into green fluorescence emission,and the fluorescence intensity is also enhanced.After fumigation with triethylamine,it will return to its original state.After Dpa-Pr-F acid fumigation,the phosphorescence lifetime increased to 47ms,and the phosphorescence intensity was also enhanced,which is due to the influence of the protonation/deprotonation of the pyridine unit on the luminescence properties.Also,Dpa-Pr exhibits different colors of luminescence in organic solvents of different polarities and has good intramolecular charge transfer(ICT)characteristics.The designed and synthesized materials with phosphorescence and fluorescence can be used for the detection of volatile organic pollutants(VOCs)and the detection and analysis of organic pollutants of polycyclic aromatic hydrocarbons(fluorene,anthracene,etc.).It can also analyze and identify environmental pollutants by fluorescence spectroscopy or phosphorescence spectroscopy.