Study On The Supramolecular Interaction Between Calixpyridinium Salts And Inorganic Anions And Its Applicatio

Supramolecular chemistry is the study of molecular aggregates based on non-covalent bond interactions between molecules.Supramolecular chemistry has been widely used in chemical catalysis,surfactant,drug delivery and other fields due to its self-assembly properties and molecular recognition function.Macrocyclic molecules are at the heart of supramolecular chemistry.Crown ether,cyclodextrin,calixarene,cucurbituril,pillararene and so on,are a class of macrocyclic compounds with intrinsic cavities that can bind certain guest molecules.Among them,water-soluble macrocycles have attracted much more attention because water-solubility enables such macrocycles to explore potential applications in aqueous solution of life systems.Calixpyridinium is a kind of easy-to-get water-soluble cationic macrocyclic compound.In recent years,this macrocycle has attracted wide attention due to its excellent bonding ability with various organic anions in aqueous solution.However,the bonding possibility of cationic macrocyclic calixpyridinium with various inorganic anions has not been explored.In order to better reveal the host–guest interactions between calixpyridinium and inorganic anions,we carried out the following work:1.The supramolecular assemblies constructed by calixpyridinium and three typical Keggin-type polyoxometalates（POMs）,phosphotungstic acid(PTA,H₃PW₁₂O₄₀),silicotungstic acid(STA,H₄Si W₁₂O₄₀)and phosphomolybdic acid(PMA,H₃PMo₁₂O₄₀)were studied.The results showed that all three polyoxometalates could bind calixpyridinium with a n:n stoichiometric ratio to construct organic-inorganic hybrid calixpyridinium-POMs assemblies by the strong electrostatic interactions.Interestingly,the three assemblies were all irregular spherical nanoparticles but with quite different sizes.In the order of particle size from small to large,they were calixpyridinium-PTA assembly,calixpyridinium-STA assembly and calixpyridinium-PMA assembly.A large number of precipitates were formed with the addition of acid to the calixpyridinium-PTA or calixpyridinium-PMA solution.2.Since the above calixpyridinium-PTA assembly and calixpyridinium-PMA assembly could generate a large number of precipitates under acidic conditions,which were expected to be applied in the adsorption of dyes,we then studied the adsorption of calixpyridinium-PTA assembly and calixpyridinium-PMA assembly on dyes under acidic conditions.The results showed that the cationic dyes such as crystal violet（CV）,methylene blue（MB）and rhodamine B（Rh B）could be selectively adsorbed by the calixpyridinium-PTA assembly and calixpyridinium-PMA assembly under acidic conditions.In addition,the three calixpyridinium-POMs assemblies all had certain dye removal effect in the presence of H₂O₂ and light.The smallest calixpyridinium-PTA assembly had the most excellent removal effect on organic dyes,such as CV,eriochrome black T（EBT）and congo red（CR）.This effect became worse and worse by using larger and larger assembly.This study not only gave a structure-function relationship of the calixpyridinium-POMs assemblies,but also supplied an alternative green and convenient method for the removal of organic dyes from wastewater.3.Calixpyridinium（calixpyridinium·4Br^-）was a water-soluble cationic macrocyclic compound containing four counter bromide anions.Inspired by the fact that calixpyridinium could bind POMs as a family of discrete molecular metal-oxide anionic clusters,we then studied the bonding interactions of calixpyridinium with a series of simple inorganic anions.It was found that the macrocyclic structure of calixpyridinium could bind S₂O₅^2-,HSO₃^-,HSO₅^-and Br^-but could not bind F^-,Cl^-,NO₃^-,HSO₄^-,H₂PO₄^-,SO₄^2-and S₂O₈^2-.Unlike the bonding between calixpyridinium and organic anions driven by electrostatic interaction,charge-transfer interaction andπ-stacking interaction,the size matching effect between the cavity of calixpyridinium and the inorganic anions encapsulated into the cavity may be the major factor in the effective bonding of calixpyridinium and inorganic anions.The more inorganic anions enter the calixpyridinium cavity,the weaker the bonding strength between calixpyridinium and this inorganic anion.In addition,the protection of inorganic anion by the molecular recognition of macrocyclic calixpyridinium was further applied in preventing dye from degradation and fading,and preventing antibiotics from degradation and failure.