Studies Of Novel Building Blocks Based On The Diverse Reactivities Of Pyrylium Salts And Their Self-assembling Properties

As an important member of six-membered oxacycles,pyrylium salts have been widely used in enormous fields because of their diverse reactivities and unique photophysical properties.Defined as "chemistry beyond molecule",the core of supramolecular chemistry lies in the self-assembly of supramolecular building blocks,Fulfillment of the controllable and ordered self-assembly of supramolecular building blocks has always been a hot topic in supramolecular chemistry.The rational construction of supramolecular building blocks is a prerequisite to this goal,and pyrylium salts had been rarely utilized in this area.In this dissertation,a series of novel supramolecular building blocks with different noncovalent interactions were constructed by utilizing the diverse reactivities of pyrylium salts and their rigid backbones and characterized with 1H-NMR,13C-NMR,and MS.The self-assembly behaviors of the building blocks were studied and the controllable and ordered self-assembly was fulfilled step by step.In this process,the diverse reactivities of pyrylium salts have also been discussed and studied in depth.The detailed research contents are as follow:1.Studies of organic ?-gelators based on van der Waals force and ?-interactions and their properties.Two organic ?-gelators were successfully synthesized by a sequential reaction of the nucleophilic reaction of pyrylium salt with CH3COONa,Suzuki coupling reaction,and esterification reaction.Both of them can gelate several organic solvents as the result of the ?-?interactions and van der Waals force.However,a subtle difference in the position of the N atom at the pyridine ring greatly affected their fluorescence and gelation properties.Fluorescence spectrometry,theoretical calculations,rheological studies,PXRD studies were conducted to illuminate the differences between their gelation,fluorescence,self-assembly morphologies and sensing properties.2.Studies of a supramolecular polymer based on host-guest interaction and coordination and its properties.A novel host molecule with four terpyridine groups as coordination sites and one pillar[5]arene unit as a linker was constructed with pyrylium salt as the starting material,followed by nucleophilic reaction of pyrylium salt with CH3COONa,Suzuki coupling,and etherification reaction.After the introduction of Zn2+ and a guest molecule that interacts with pillar[5]arene,a cross-linked supramolecular polymer was generated.The photophysical properties,self-assembly process,and stimuli-responsiveness were carefully studied with fluorescence spectrometry,UV-vis spectrometry,1H-NMR,viscosity,DLS,SEM and TEM tests.3.Studies of the Suzuki coupling reaction of pyrylium salts.A series of new pyrylium salts containing terpyridine groups were synthesized by the Suzuki coupling reaction of pyrylium.salts,followed by a cyclization reaction under acidic condition.The studies showed that two reactions were involved in the Suzuki coupling step of pyrylium salts.One is the coupling reaction between boronic acid(or boronic acid pinacol cyclic ester)and organohalide catalyzed by palladium under basic condition,and the other is the nucleophilic reaction between pyrylixum salt and OH-,which led to the formation of unsaturated 1,5-diketone.Under acidic conditions,unsaturated 1,5-diketone was unstable and underwent a ring closure step to form pyrylium salt.4.Studies of supramolecular metallomacrocycles driven by metal-ligand coordination.On the basis of A series of multi-topic ligands with terpyridine groups were synthesized utilizing the nucleophilic reaction between pyrylium salts and primary aromatic amines.Studies revealed that driven by the coordination interaction between terpyridine and Cd2+,ligands with rigid structures effectively self-assembled into discrete concentric metallomacrocycles.Related NMR,MS,TEM and molecular simulations were employed to characterize and compare the stabilities of the metallomacrocycles.