Syntheses And Properties Studies Of Mixed-metal Clusters And Metal-organic Frameworks Based On Schiff-base Ligands

Schiff-base ligands mainly refer to a class of organic ligands containing amines or azomethines,which are usually obtained by the condensation reactions of a ldehydes or ketones and amines.Utilizing the Schiff-base ligand as a versatile building block for the design of metal-organic complexes or frameworks has attracted significant attention in recent years.It has proved to be that Schiff-base compounds and their metal complexes have important applications in the fields of medicine,catalysis,analytical chemistry and photochromism.Based on Schiff-base ligands,we successfully synthesized two nonanuclear metal-organic clusters and two metal-organic frameworks.They were characterized by elemental analysis,TG analysis,IR,UV-visible spectroscopy,single-crystal X-ray diffraction and powder X-ray diffraction?PXRD?.Moreover,magnetic studies and the oxidation of cyclohexene catalyzed by the two nonanuclear metal-organic clusters as heterogeneous catalysts were investigated.1.Two new windmill-type mixed-metal clusters based on Schiff-base ligands were designed and synthesized under solvothermal conditions.The oxidation of cyclohexene catalyzed by 1 and 2 as heterogeneous catalysts was investigated.{CuMn₂?H₂O?₂[Cu(C₁₄H₁₆N₂O₃)Cl]₆}·H₂O?1?{CuZn₂?H₂O?₂[Cu(C₁₄H₁₆N₂O₃)Cl]₆}·H₂O?2?Catalytic experiments show that compounds 1 and 2 are high activity catalysts for the oxidation of cyclohexene with 80.72%and 73.18%conversion after 12 h.The catalysts 1and 2 showed high stabilities and can be reused in two successive runs with only slightly decreased substrate conversion.Furthermore,magnetic studies suggest that antiferromagnetic interactions exist in compound 1.2.Two three-dimensional metal-organic framework materials based on Schiff-base ligands were successfully synthesized by one-step synthesis.Magnetic studies of 3 were investigated.{CdNa₂?OH??H₂O?₂[Ni₂(C₂₂H₁₈N₂O₆)₂Na?H₂O?₂]}·11H₂O?3?{CdNa₂?OH??H₂O?₂[Cu₂(C₂₂H₁₈N₂O₆)₂Na?H₂O?₂]}·11H₂O?4?Compounds 3 and 4 exhibit a distinct three-dimensional structure,which is constructed by an infinite chain[CdNa₂?CO₂?₄]_n and ML(L=C₂₂H₁₈N₂O₆;M=N i 3,C u 4)units linked through carboxylate groups.The structure possesses 1D channels of 19.29×26.94?² along the a-axis.Magnetic studies manifest that ferromagnetic interactions exist in compound 3.