Synthesis,Structure And Property Of All-heteroatom-bridged Homocalix[4]aromatics

Novel and functional macrocyclic compounds provide unique models in the study of noncovalent molecular interactions,molecular recognition and assembly.They also serve as building blocks in the construction of high-level supramolecular architectures and in the fabrication of molecular devices.Therefore,the design and construction of ingenious macrocyclic molecules has always been one of the driving forces to promote the major adva nces of supramolecular science.This dissertation focuses on the synthesis,structure and property of novel and functionalized all heteroatom-bridged homo calix[4]aromatics.We have established and developed the fragment coupling and one-pot reaction strategies which allow the introduction of increasing numbers heteroatoms and various aromatic rings in the macrocyclic skeleton.Starting from aromatic dinucleophiles such as N,N'-(1,3-phenylene)bis(hydrazine)and 2,6-dihydrazinylpyridine,the fragment coupling approach involving aromatic nucleophilic substitution reaction with 1,3-aromatic electrophiles afforded partial and all diheteroatom bridged homo calix[4]aromatics.N,O-diheteroatom bridged homo calix[4]aromatics were synthesized from the one-pot reaction of N,N'-(1,3-phenylene)bis(hydroxylamine)with dichloro substituted 1,3,5-triazines.The introduction of more heteroatoms into the linking positions of heteracaclix[4]aromatics resulted in the great expansion of the cavity size of all heteroatom bridged homo calix[4]aromatics.All aromatic rings were found to form conjugation systems with the lone pair electrons of directly adjacent heteroatoms.The repulsion of the lone pair electrons on each of the heteroatom in hydrazo(-NR-NR-,R = H,Me)and hydroxylamino(-NR-O-)was observed.The presence of two bridging heteroatoms would most probably alleviate the dipole-dipole repulsion between proximal aromatic rings,leading to the formation of diverse conformational structures including partial cone,cone to 1,2-alternate ones in the solid state.Moreover,the electronic feature of macrocyclic cavities can be regulated by heteroatoms due to their conjugation with their adjacent aromatic rings.The synthesized homo heteracalix[4]aromatics exhibit interesting properties in molecular recognition and self-assembly.Hydrazo-bridged homo calix[2]pyridine[2]triazine formed a dimeric complex with a transition metal ion such as cobalt(II)in which one of the nitrogen atoms of the hydrazo linkage also participate in binding to metal center.As a non-classical amphiphilic molecule,hydrazo-bridged homo calix[2]pyridine[2]triazines underwent self-assembly in an aqueous solution to form stable aggregates which were subject to regulation by acid,base and transition metal ions because of the interaction of macrocycles with guest additives.The rearrangement reactions of various N,O-diarylhydroxylamines were also studied.The diverse 3,3-,5,5-and 1,3-rearrangement reactions were determined by the nature and substitution pattern of the substi tuents on the aryl moieties.The transition-metal-free processes produced functionalized biaryls and unsymmetric diarylamine with excellent functional group tolerance.In summary,we have provided a new type of macrocyclic host molecules.The all heteroatom bridged homo calix[4]aromatics are conveniently synthesized,and they adopt unique conformational structures of expanded cavity sizes and show interesting binding properties in comparison to well-known heteracalix[4]aromatics.It is believed that these novel features will render all heteroatom linked homo calix[4]aromatics versatile platforms in the study of supramolecular science.The insight into the influence of heteroatoms to the macrocyclic molecules will guide us to design new generation of synthetic macrocycles.