Study On Synthesis And Catalytic Properties Of Sulfonic Acid Coordination Polymer Containing Bis(triazole)

In order to develop a series of new sulfonic acid catalysts,this paper studied on complexes with mixed ligands.Five aromatic sulfonic acids were selected as the sulfonic acid ligands?HL₁=p-toluene sulfonic acid,HL₂=benzenesulfonic acid,HL₃=3-nitrobenzenesulfonic acid,HL₄=4-nitrotoluene-2-sulphonic acid,HL₅=5-sulfosalicylic acid?,and 1,3-bis?1H-1,2,4-triazole?propane?btp?was acted as a flexible ligand.They reacted with the first period of transition metals Co?II?,Ni?II?,Zn?II?,Cu?II?to synthesize eight sulfonic acid coordination polymers containing triazole ligands by normal temperature volatilization method and hydrothermal?solvent?method.Eight coordination polymers are[Co?L₁?₂?btp?₂]_n?1,CCDC:1920593?,[Ni?L₁?₂?btp?₂]_n?2,CCDC:1952546?,[Zn?L₁?₂?btp?₂]_n?3,CCDC:1920594?,[Cu?L₁?₂?btp?₂]_n?4,CCDC:1952548?,[Cu?L₂?₂?btp?₂]_n?5,CCDC:1973236?,{[Cu?L₃?₂?btp?₂]·2H₂O}_n?6,CCDC:1973241?,[Cu?L₄?₂?btp?₂]_n?7,CCDC:1952536?,and{[Cu?L₅?₂?btp?₂]·2H₂O}_n?8,CCDC:1973246?.Among the eight complex synthesized,complex 1-4 show similar spatial structure.They all belong to the Monoclinic crystal system,P2₁/c space group,the central metal is coordinated with the p-toluenesulfonic acid ligand,and the btp ligand is used to anti-gauche conformational bridges form a 2D layered structure.The complex 5 belongs to the Monoclinic crystal system,P2₁/n space group,the central metal is coordinated with a benzenesulfonic acid ligand,and the btp ligand is bridged to form an anti-gauche conformational2D structure Layered structure.The complex 6 belongs to the Monoclinic crystal system,P2₁/n space group,the central metal is coordinated with the3-nitrobenzenesulfonic acid ligand,and the 1D chain structure is formed by the btp ligand in the anti-anti conformation bridge.It is linked to hydrogen bonds formed between sulfonic acid groups and free water between chains.The complex 7 belongs to Triclinic crystal system,P^-11 space group,the central metal is coordinated with 4-nitrotoluene-2-sulphonic acid ligand,and the 1D chain structure is formed by the btp ligand in the anti-gauche conformation bridge.The complex 8 belongs to the Triclinic crystal system,P^-11 space group,the central metal is coordinated with the 5-sulfosalicylic acid ligand,and the1D chain structure is formed by the btp ligand in the gauche-gauche conformation.There are hydrogen bonds in the chain.Chains are linked by hydrogen bonds between sulfonic acid groups and free water.At the same time,the complexes 1-8 showed good thermal stability,which provided the foundation for its application as catalysts.In order to provide theoretical support for ligand selection in the design and synthesis of sulfonic acid complexes,the density functional theory?DFT?was used to geometrically optimize the btp ligand and the sulfonate anion.The electrostatic charge distribution was calculated according to the geometric parameters measured by X-ray single crystal diffraction method.Finally,eight coordination polymers were successfully used as heterogeneous catalysts in Biginelli reaction,and they showed excellent catalytic activity.The complex 3 is the most prominent,which not only has high catalytic activity but also has good reusability.The results show that a series of new heterogeneous catalysts with mixed ligand have been successfully obtained.