Synthesis And Property Investigation Of Novel Organic Materials With "AIE+ESIPT" Characteristics

Luminescent materials with aggregation-induced emission(AIE)property have received increasing attention in recent years and have been successfully applied in fluorescence probes or biosensors,bioimaging,OLEDs,optical waveguides,liquid crystal display,stimuli-responsive systems and so on for their efficient aggregate state emission and unique fluorescence "turn on" process.The emission wavelength and intensity of AIE-active compounds in the solid or aggregation state can be modulated by changing the composition of molecules,spatial conformation and accumulation patterns,which overcome the aggregation-caused quenching(ACQ)shortcoming of traditional fluorescent molecular.Herein,we have designed and synthesized a series of compounds with AIE performance based on coumarin and salicylaldehyde derivatives by readily available Schiff base condensation reactions.The central content of this dissertation is as follows:1?A novel colorimetric and ratiometric fluorescence probe(4-[[(7-hydroxy-4-methyl-2-oxo-2H-1-benzopyran-8-yl)methylene]amino]benzoic acid,CPA)for the selective and sensitive monitoring of cysteine based on a coumarin Schiff-base platform was developed.This probe exhibited remarkable AIE characteristics with an exceptionally large blue shift(125 nm),which showed low emission in DMSO but strong aggregation-induced emission in water solution.An excellent linear relationship of fluorescence intensity ratio(F450/F575)(R2=0.9922)versus Cys concentration in the range of 0.1 ?M-13.0 ?M was obtained.2.An coumarin based red AIE fluorogen(8-[[[4-(dimethylamino)phenyl]imino]methyl]-7-hydroxy-4-methyl-2H-1-benzopyran-2-one,CDPA)was successfully synthesized by readily Schiff base reaction.Due to both the ESIPT and TICT processes,CDPA exhibits a strong red emission(?em=645 nm)with long emission lifetimes,an extraordinarily large Stokes shift of about 245 nm and high fluorescence quantum yield of 26.3%in solid state.The uniquely high quantum yield and rational tuning emission are demonstrated to originate from a combination effect of the molecular stacked design,ESIPT-active intramolecular H-bond,and TICT.With high red fluorescence quantum efficiency in solid states,good selfassembly performance,and significant TADF property,CDPA show potential application as remarkable emitter in the doped OLEDs,showing much high EL efficiencies.Additionally,the emitting device based on 3 has been successfully fabricated,achieving a maximum brightness of 1675 cd/m2 at 14 V(225 mA/cm2)with the CIE coordinates of(0.51,0.49).Standing on this basis,not only is fine tuning the energetics of ESIPT of fundamental importance but also paves a new and feasible avenue route to yellow light generation.On the other hand,the finding is the first to show that coumarin derivatives possess the good photoelectric properties and can be used as luminescent materials in OLEDs.3.Three new Schiff base derivatives 5-(diethylamino)-2-[[[4-(dimethylamino)phenyl]imino]methyl]phenol(C1),2-[[(4-(dimethylamino)phenyl)imino]methyl]-4-fluorophenol(C2)and 5-(diethylamino)-2-[[(4-nitrophenyl)imino]methyl]phenol(C3)possessing AIE and ESIPT characteristics with various fluorescence emissions from green to red and high fluorescence quantum yields in the aggregated state were synthesized using a facile and efficient method.Then,the effect of substituted group types and positions on the fluorescence of these novel compounds was investigated through fluorescence spectra analysis and theoretical calculations.And it was found that the different substituent groups in the salicylaldehyde moiety and in phenyl group produce the difference of optical properties,and these multiple-colour AIE molecules have a potential application of novel pH and Zn2+ chemosensors.4.A series of red to near-infrared(NIR)emissive organic compound 3-[4-(dimethylamino)phenyl]-1-(2-hydroxyphenyl)-2-propen-1-one(L1),1-(2-hydroxy phenyl)-3-[4-(1-pyrrolidinyl)phenyl]-2-propen-l-one(L2)and 3-[4-(diphenylamino)phenyl]-1-(2-hydroxyphenyl)-2-propen-1-one(L3)based on the 2'-hydroxyaceto-phenone derivatives were synthesized through a mild condensation reaction,which exhibit typical AIE properties,long fluorescence lifetime,the high quantum yield in an aggregated state.Comparison of their fluorescence properties clearly gives evidence that a subtle structure modification can arouse great property changes,which is instructive in designing new high-efficiency organic luminescent materials.In demonstration of the potential of this new fluorescence dye L2,the fluorescence probe 4(2-[3-[4-(pyrrolidin-1-yl)phenyl]acryloyl]phenyl acrylate)that is capable of unique detecting Cys in water media is also constructed successfully.