The Construction And Catalysis Of Thiourea-based Metal-organic Complexes

Coordination driven self-assembled metal-organic complexes are widely used in molecular recognition,selective catalysis and enzymatic chemistry,due to the well-defined cavity and the unique physical and chemical properties.Based on high symmetry,controllability and structural stability,Metal-organic macrocycles(MOMs)are a promising multifunctional material.As the focus of research,the properties of MOMs constructed by regulating functional organic ligands and metal nodes are superior to those of organic ligands and metals.The thiourea group has good redox activity,and S and N atoms can coordinate with metal ions,so it is introduced into the ligands as a bidentate chelator.In this paper,based on two novel thiourea-based ligands,a series of MOMs and a metal-organic molecular flask were constructed.With its excellent reducibility,it is used as a heterogeneous catalyst for copper-catalyzed azide-alkyne cycloaddition(CuAAC).Two similar thiourea-based ligands combined with photosensitive carbazole groups,DCT1 / DCT2,are designed and synthesized,which construct two MOMs(CuI-DCT1,Ni-DCT2)and one metal-organic “molecular flask”(Cu-DCT1).The single crystal structure data uncover that CuI-DCT1 realizes the unsaturated triple coordination structure of Cu(I),and Cu-DCT1 realizes tetrahedron-shaped four-coordinated copper.The Ni center of Ni-DCT2 is distorted unsaturated four-coordinate configuration,which is coordinated with two coordination sites of "NS" from two ligands DCT2,respectively.Copper-based metal organic macrocycle,CuBr-DCT1,has good photoactivity and strong reduction performance and is able to maintain structural stability in various organic solvents.When it is used as heterogeneous catalyst for CuAAC,high conversion efficiency of the reaction is achieved,and the catalyst is easily separated and recovered.CuBr-DCT1 exhibits excellent catalytic effect on CuAAC.Under room temperature and the irradiation of household energy-saving lamps,conversion rate is up to 100%,with no other by-product.CuAAC is the most valuable reaction in "click chemistry" and the products 1,2,3-triazole are widely used for pharmaceutical research,material chemistry and polymer science.However,Cu(I)salts are prone to experience disproportionation or oxidation reactions,and cannot be effectively separated or reused in homogeneous catalytic systems.Thus,as a stable heterogeneous catalyst for the CuAAC,the structural assembly and catalysis of CuBr-DCT1 is important and meaningful for biological applications.