Synthesis And Application Research Of Polyimidazolium-Based Macrocycles And Cages

Recently,poly-NHC?N-Heterocyclic Carbene?ligands attracted considerable interest due to their unique chemical properties.Up to now,many metal-carbene supermolecular assemblies featuring poly-NHC ligands?bis-NHC,tris-NHC,tetrakis-NHC?have been reported.However,the research mainly concentrates on the simple synthesis and structural characterization of the organometallic poly-NHC complexes,the corresponding functional modification of metal-carbene supermolecular assemblies are rare.Given it,poly-NHC precursors bearing terminal N-cinnamic ester substituents were designed and synthesized.A series of metallacycles and metallacages were successfully constructed via the formation of metal-carbene bond.The photochemical modification and removal of metal centers of these assemblies resulted in the formation of novel octakisimidazolium macrocycles and hexadecakisimidazolium cage.In addition,a series of new compounds were characterized by means of NMR,mass spectrometry and UV-vis spectrum.The specific contents are as follows:In the first part,the N-cinnamic ester-modified tetrakis-NHC precursors H₄-L?PF₆?₄?L=1a,1b?were designed and synthesized.Two different organometallic assemblies[Ag₄?L?₂]?PF₆?₄?L=1a,1b?were successfully constructed via a“one pot”reaction with Ag₂O.These metallacycles can be effectively modified by double[2+2]photocycloaddition under UV irradiation in solution,and the metallacycles[Ag₄?L?]?PF₆?₄?L=2a,2b?that contain two cyclobutane were also obtained.The removal of the central silver ions afforded new macrocyclic compounds featuring eight imidazolium groups.In the second part,we designed and synthesized the tetragonal octakis-NHC precursor H₈-3?PF₆?₈.A cylinder-like octanuclear Ag^I hexadecacarbene assembly[Ag₈?3?₂]?PF₆?₈ was obtained through the reaction of H₈-3?PF₆?₈ with Ag₂O.The organic cage compound containing sixteen imidazolium moieties was prepared by a quadruple[2+2]photocycloaddition and removal of the template metals from metallacage[Ag₈?3?₂]?PF₆?₈.Furthermore,the fluorescence titration experiments were used to explore its the properties of host-guest chemistry,which reveals a high visual fluorescence“turn off”effect on HPTS.