Research On The Multicomponent Reaction Synthesis,Optical Properties And Application Of Tetrahydropyrimides And Maleimides

Aza-heterocyclic compounds,characterized by wide varieties,unique bioactivities,are an important branch of heterocyclic compounds.Aza-heterocyclic compounds have been widely used in the fields of medicine and biology.In addition,many aza-heterocyclic compounds have been used in application areas such as biological imaging,fluorescent probes and fluorescent materials owing to their excellent optical activity.Therefore,aza-heterocyclic compounds are of great interest to the researchers of pharmaceutical chemistry,synthetic chemistry,analytical chemistry and materials chemistry.In 2011,we have developed an efficient five-component reactions(5CR)for the synthesis of a novel series of racemic C6-unsubstituted tetrahydropyrimidines(THPs)and found that the THPs exhibited strong aggregation-induced emission(AIE)characteristics.The AIE characteristics is that AIE compounds show no emission in solution but become strong fluorescene upon aggregation.Over the past decade,AIE compounds have shown great advantages in wide application areas such as fluorescence senor and biological imaging.Unlike other reported small organic AIE compounds,THPs do not have rotatable aryl groups connected on π-conjugated system.Unique molecular structure usually possess unique properties and applications.We have found that THPs possess unique and high sensitive temperature property and show practically no emission in surfactant micelles and can be used as fluorescent sensors for the critical micelle concentration of ionic surfactants,and temperature.Recently,we also found that THPs exhibit sensitive mechanofluorochromic properties.This thesis focuses on synthesizing different-structure THPs via the SCR that we developed in order to study their mechanofluorochromic properties,mechanism,application,and put forward the relevant mechanism.We found that the conversion between the paired RS packing and unpaired RR/SS packing of enantiomers is the primary reason for the different solid state emissions.The mechanism is reported for the first time,which affords a new methodology for the exploration and design of new mechanofluorochromic compounds.And we also make a exploration on the application that the THP-1 are used in cell imaging as nanoparticles.In addition,the multicomponent reaction synthetic method of another aza-heterocyclic compounds aminomaleimides(AMIs),and their fluorescence-structure relationship have been studied in detail.A simple and efficient three-component reaction has been developed for the synthesis of AMIs with different substituents.We found that AMIs skeleton is a good fluorophore,with high fluorescence quantum yields.The emissions of AMIs in monomers will be quenched in protic solvents by hydrogen bonding effect for alkyl monosubsituted aminomaleimides(alkyl MAMIs),in protic and nonprotic polar solvents by twisted intramolecular charge transfer(TICT)for alkyl disubsituted aminomaleimides(alkyl DAMIs)or in polar and nonpolar solvents by the rotations of aryl for aryl MAMIs/DAMIs.The solid fluorescence quantum yields of AMIs depends on molecular packing modes.Intermolecular N-H…O and π-π stacking interaction are two important factors influencing molecular packing of AMIs.For dialkyl or aryl/alkyl MAMIs,they are connected as dimers via N-H…O hydrogen bonding,and the dimmers are packed as parallel stairs of high fluorescence quantum yields by intermolecular π-π stacking interaction.For diaryl MAMIs,the molecules are connected as layers via intermolecular N-H…O hydrogen bonding,and the molecules are placed as zigzag lines of low fluorescence quantum yields by intermolecular π-πstacking interaction.For DAMIs,the molecules forms no emissive dimmers by π-π stacking interaction in central rings.The research results have an important significance for promoting their biological activity research and biological fluorescent probe research.