Synthesis,Properties And Catalytic Application Of Microspheres Based On Poly-imidazolium Salts Containing Triphenylamine

Palladium has been extensively used as a catalyst in C-C coupling reactions.Homogeneous palladium catalysts may achieve excellent activity and selectivity under mild reaction conditions,but efficient separation and subsequent recycling of homogeneous catalysts remains a scientific challenge.The heterogenization of homogeneous catalysts has been shown to be one of promising solutions.In thr context,sherical polymers are attractive supports of palladium catalysts owing to their uniform size,large surface area and tunable chemical structure.Main-chain imidazolium-based ionic polymers are regarded as a new type of organic polymer supports,their structrural frameworks may bear charging units and coordinating units,which can efficiently prevent the agglomeration and loss of palladium during reaction and separation through steric,electrostatic and coordination interaction.In the dissertation,we present a series of main-chain poly-imidazolium salts microspheres,which are readily available through quaternization of tris(4-imidazolylphenyl)amine and aromatic ligands containing poly(bromomethylene)groups.Their uniform spherical morphologies can be modified through judicial selection of solvent,temperature,concentration and aromatic ligands containing bromomethylene units.Palladium is easily introduced into these imidazolium-based ionic polymers through anioic metathesis to form heterogeneous catalytic systems.The dissertation presents the following conclusions:(1)in the formation of uniformly spherical main-chain imidazolium-based ionic polymers based on 9,10-bis(bromomethyl)anthracene and tris(4-imidazolylphenyl)amine,the polarity of solvents,concentration of monomers and reaction temperature all could affect the particle morphology of polymer products,where dimethylformamide is the most ideal solvent,while other solvents were not suitable to generate uniform spherical particles;(2)seven types of poly(bromomethylene)monomers were chosed to investigate the influence of monomers on the polymer morphologies,only three type of polymeric microspheres were generated from 9,10-bis(bromomethyl)anthracene,1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene,1,2,4,5-tetrakis(bromomethyl)benzene,the average diameter of spherical particles are 1200,350,400 nm,respectively;(3)introduction palladium acetate into the poly-imidazolium salts based on 1,2,4,5-tetrakis(bromomethyl)benzene monomer generates the supported Pd catalysts.The catalytic system shows excellent activity and reusability in Suzuki coupling reaction between 4-bromoacetophenone and phenylboronic acid.The uniform spherical morphology is well maintained after 9 consecutive runs.However,the supported Pd catalysts based on poly-imidazolium salts based on 1,3,5-tris-(bromomethyl)-2,4,6-trimethylbenzene and 9,10-bis(bromomethyl)anthracene can be recycled 2 and 4 runs,respectively.