Synthesis,Characterization and Photochemical Modification of Coumarin-Decorated Poly-NHC Metal Assemblies

Author:Sun Li Ying

Supervisor:han ying feng

Database:Doctor

Degree Year:2019

Download:30

Pages:151

Size:8341K

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The design and synthesis of organometallic functionalized assemblies based on poly-NHC(N-Heterocyclic Carbenes,NHC)ligands has been a rapidly developing field.Various two-dimensional and three-dimensional metal-based supermolecular assemiblies with different shape and size have been constucted by utilizing different NHC ligands coordination with appropriate metal ions.The thesis focuses on the synthesis of metal-carbene supermolecular assemblies by using poly-NHC ligands(bis-NHC,tris-NHC,tetrakis-NHC)with coumain pendants.Subsequently,we investigate the structure character of these assemblies and their photochemical post-modification by combining single-crystal X-ray diffraction with UV-visible light spectra and other characterization methods.The specific content is as follows:1.Demonstrate the use of bis-NHC ligands with coumain pendants synthesizing corresponding metallacycles via self-assembly.In the obtained dinulear metallacycles,pairs of coumarin pedants from different ligands exists in close proximity and upon irradiation they stereoselectivity form syn-HH cyclobutanes with high conversion rates.As a result of the double[2+2]cycloaddition,new tetracarbene macrocycles coordinated to two Mental(I)centers were abtained.2.A procedure for the synthesis of three-dimensional hexakisimidazolium cage compounds has been developed.Design new kinds of tri-(NHC)ligands and synthesize corrosponding tricabene metal framworks.Subsequent UV irradiation gave three cyclobutane links between the two tris-NHC ligands in three[2+2]cycloaddition reactions,thereby generating a three-dimensional hexakis-NHC ligand.Removal of the metal ions resulted in the formation of the first sample of threedimensional hexakisimidazolium cages with a large internal cavity.3.Synthesis a heteroligand metal-carbene complex in this part.Demonstrated narcissistic and social self-sorting during the formation of assemblies of type tricabene metal framworks.Subsequently,the photochemical reaction of the complex was studied.Found reaction of a mixture of trisimidazolium salts featuring either an electron-poor triazine backbone(H3-A(PF6)3)or an electron-rich benzene backbone(H3-D(PF6)3)of identical size with Ag2O gave cleanly the heteroligand assembly[Ag3(A)(D)](PF6)3.In addition,the photochemical reaction rate of heteroligand metal-carbene complex is 4-5times than monoligand metal-carbene complex due to donor-aceptorπ···πstacking interaction between the electron-rich and electron-poor ligand.4.A novel tretra-imidazolium ligand has been synthized based on tretraphenyl ethylene chromophore.The benzimidazolium which is almost nonluminescent shows great enhancement of fluorescence due to the immobilization of silver(I)carbene on the tetraphenyl ethylene chromophore in dilute solution.The photochemistry reaction of silver carbene complexes with parallel arrangement of coumarin pedants is promoted,resulting in the formation of silver carbene framework with two cyclobutanes.In addition,we also studied the optical properties of the series of compounds in solution.