Design,Synthesis And Application Of Dendritic Polyphenyl Silane With Aggregation Induced Emission Property

Fluorescent materials have important applications in optoelectronic device,molecular sensing,and biological probes.The aggregation caused quenching(ACQ)effect of traditional fuorescent materials leads to limitations in pratical applications Fortunately,a novel fuorescent material with agregation-induced emission(AIE)property was discovered by Tang et al.and has attracted much attention due to the excellent emission properties and wide applications.The AIE molecules containing silicon have emission enhancement and color adjustment properties,which is caused by "silicon-cored structure".This was called "silicon-cored effect".The silicon containing compounds also exhibit high thermal stability and high glass transition temperature.“Memory effect" can be applied in varies fields,such as thermally response ceramics and shape memory plastics.More and more organic materials based on supramolecular orientational memory effect have been designed and fabricated.Based on the knowledge we mentioned above,several AIE molecules were designed and synthesized,their fluorescence properties and applications as sensors were investigated.Firstly,three dendritic polyphenylbenzenes and four silicon-containing derivatives were designed and synthesized.A comprehensive systematic study of fluorescence properties was performed.The seven polyphenylene compounds exhibit aggregation-induced emission enhancement properties.Compared to the three dendritic polyphenylbenzenes,the silicon-containing polyphenylbenzene has a stronger fluorescence emission.These derivatives also showed a visible blue light in contrast to the colourless emission of polyphenyl compounds.The reason for this phenomenon is mainly that the tetrahedral silicon-core structure can effectively attenuate the π-π stacking of molecules in the aggregate state;the reported"silicon-cored effect" was further proved.The volume effect and unique spiral arrangement make the trimethylsilyl-substituted compound shows fluorescence enhancement and color adjustment.So,the results should be "silicon effect" not merely the "silicon-cored effect".This work provides guidance for designing AIE molecules and silicone chemistry.Based on the above studies,we suspect that the electron-rich thiophene group can be introduced into the silicon-containing polyphenylbenzene,so that the obtained compound not only has AIE properties,but also can be used as a fluorescent probe to detect electron-deficient nitrate.Therefore,thiophene-functionalized polyphenyl silicon-containing derivative:bis(3,4-diphenyl-2,5-dithienyl)trimethoxysilane.(DPTB-MPS)and 3,4-diphenyl-2,5-dithienyltrimethoxysilane(DPTB-TMS)were synthesized.It was found that they exhibit AIEE properties.As a fluorescent probe,the fluorescence quenching behavior was further studied.The two compounds exhibit good properties in detecting nitroaromatics,particularly the picric acid.The quenching efficiency is higher in water-based solutions than in organic-based solvents.The quenching mechanism for detecting nitrobenzene and m-dinitrobenzene is electron transfer,but for picric acid the quenching mechanism is the coexistence of electron transfer and energy transfer.This work provides the basis for the design of organosilanes with anti-conventional optical properties and nitroaromatic fluorescent probes with AIEE properties.Thiophene has the ability to bind to metal ions.We hypothesize whether thiophene-functionalized silane fluorescent molecules can be used as fluorescent probes for ferric ions.DPTB-MPS and DPTB-TMS were dispersed in the aqueous solution,the fluorescence emission gradually decreased as the content of ferric ions increased.In addition,we also synthesized a non-silicon compound:2,3-diphenyl-1,4-dithienylbenzene(DPTB).It was found that the detection efficiency of DPTB was lower than that of DPTB-MPS and DPTB-TMS.The detection limits of ferric ions for DPTB-MPS,DPTB-TMS and DPTB to be 1.54 μM,1.17 μM and 5.28μM.The detection mechanism is static quenching.This is an excellent multiple response fluorescent probe for both nitrobenzene and ferric ions.Moreover,A new type of fluorescence molecular,named 6-(1,3-dioxo-4,5,6,7-Tetraphenylisoindoline-2-yl)hexanoic acid(TPHA)was designed and synthesized.In an acidic THF/water mixed solvent,the fluorescence intensity increases gradually as the water content increases.In addition,the fluorescence intensity of TPHA is greatly affected by pH:at higher pH,the TPHA molecule can be uniformly dispersed in the solvent,thus almost no fluorescence is detected.At lower pH,the carboxyl group of TPHA exists in the form of COOH,and the solubility of TPHA molecules decreases,resulting in enhanced fluorescence.The protonation and deprotonation process of TPHA was confirmed by both dynamic light scattering and Tyndall phenomenon.Since protamine is a positively charged protein,it can interact with negatively charged-COO-.Therefore,when protamine is added to the alkaline solution of TPHA,the fluorescence of TPHA solutions is gradually enhanced(turn on).The detection limit was calculated to be 4.78 ng/mL.In addition,heparin can bind to protamine in the TPHA-protamine complex,thereby releasing TPHA,which ultimately leads to a decrease in fluorescence(turn off).The molecule can be used as a fluorescent probe for protamine(turn on)and heparin detection(turn off).In addition,four carboxyl dendrimers,XW-081,XW-085,XW-090,and SW-118 were synthesized.X-ray diffraction patterns show that the four dendrimers are columnar hexagonal phase(Φh)at room temperature.The dendrimers rearranged into body-centered cubic phase(BCC)at higher temperature.Cubic axes are preserved upon cooling to the columnar.It shows a distinct orientation memory effect.This study enriches the class of organics with oriented memory effects.