Design, Synthesis And Characterization Of Tetraphenylethene Pyridinium Salt Derivatives

Since the aggregation-induced emission phenomenon was reported by Prof.BenZhong Tang in 2001,it has stimulated great interest among researchers,and its applications have involved organic light-emitting diodes,CPL devices,stimulusresponsive materials,bioimaging,drug delivery,ion detection,and many other fields.A variety of AIE molecules with new functions and applications have been developed,among which,tetraphenylethene derivatives have become a research hotspot due to their simple synthesis method,high modifiability and sensitive fluorescence response.In this thesis,the design,synthesis and properties,applications of novel tetraphenylene AIE materials will be studied from the following two aspects:(1)The research on the regulation of fluorescence properties of AIE materials is of great significance,and it is the basis for enriching the application and development of AIE materials.For more than two decades,research in this direction has focused on the design and construction of new luminescent molecular skeletons or the regulation of luminescence through the nature of substituents,with less research on the effects of different positions of substituents on luminescence properties and applications.We designed and synthesized three tetraphenylethene pyridinium salt derivatives with different positional substitutions,TPE-o-Py-C2,TPE-m-Py-C2 and TPE-p-Py-C2,and studied the effect of positional isomerization on the luminescence properties.The results showed that in the water-acetonitrile mixture,the compounds were unable to aggregate due to their good water solubility,and thus had no AIE properties;in the THF-Hex mixture,the compounds all showed good AIE properties.By aromatic substitution modifications at different positions,compounds with different degrees of intramolecular conjugation can be obtained,which affects the luminescence.TPE-oPy-C2 and TPE-p-Py-C2 have a long-range conjugated structure with fluorescence emission in the non-aggregated state,while TPE-m-Py-C2 has a two-stage conjugated structure with weak fluorescence emission in the non-aggregated state,and its solid fluorescence is weaker and emission peak is more blue-shifted compared with that of ortho-or para-substitution.In addition,TPE-m-Py-C2 and TPE-p-Py-C2 are capable of fluorescent"off-on" response to ClO4-and PF6-under water-soluble conditions,they can be used for the detection of inorganic explosive chlorates and PF6-in aqueous environment.(2)There have been many reports on the application of host-guest chemistry to modulate the luminescent properties of compounds.Based on the previous section,we designed and synthesized three tetraphenylethene pyridinium salt derivatives with twelve-carbon long alkyl chains,TPE-o-Py-C 12,TPE-m-Py-C 12,and TPE-p-Py-C 12,and studied the effects of long hydrophobic chains on the luminescence properties of these compounds and the host-guest interactions with α,β,γ-cyclodextrins.The results showed that the introduction of long carbon chains increased the hydrophobicity of the compounds,TPE-m-Py-C12 and TPE-p-Py-C12 had AIE properties with red-shifted fluorescence emission peaks in the H2O-DMSO mixture.The results of host-guest interaction showed that γ-CD had a good host-guest interaction with TPE-p-Py-C12 and could enhance its fluorescence emission;the solid fluorescence of the complex obtained after the host-guest interaction of γ-CD with TPE-m-Py-C12 was still weak,but the fluorescence was obviously enhanced after grinding,and a new mechanical luminescent material was constructed using the host-guest interaction,enriching the application and development of tetraphenylethene pyridinium salt derivatives.