Syntheses, Structures And Magnetic Properties Of Schiff-Base Transition Metal Complexes

In this work, three kinds of polydentate Schiff-base ligands with salicyl (H₃Sea, H₄amp,H₃Salp) have been designed and synthesized as the building block to construct polynuclear clusters. 17 transition metal complexes of Schiff-base ligands have been obtained by employeing various magnetic ions (Mn²⁺, Fe^2+/3+,Co²⁺, Ni²⁺, Cu²⁺) in the molecule assembly through hydrothermal synthesis and room temperature volatilization methods. The structures and magnetic properties of the crystals have also been characterized. The influences of reaction conditions, solvents and ratios on the structure and magnetic properties of products have been systematically discussed. The paper includes five aspects as following:1. Different products were obtained by changing the solvents of hydrothermal reactions carried out on cobalt ions and H₃Sea/H₄amp. The results show that solvent plays a very important role in the formation of product especially in the structure and magnetic properties, alcohol solvents with active oxygen atoms can act as a coordination agent, whereas things were different when MeCN was used, anions were coordinated instead of solvent.2. The same products can be obtained no matter what kind of solvent or ratio was used in the reactions carried out on cooper/nickle ions and H₃Sea/H₄amp at room temperature. The results show that neither the solvent nor the ratio has significant effect on the formation of products.3. Different products were obtained by changing the ratio or little ligands of hydrothermal reactions carried out on cobalt ions and H₃Salp. The results show that the ratio can influence the structure of product, and little ligands which act as a coordination agent have more iobvious influence on the magnetic properties of the products.4.Different products were obtained by changing the little ligands of hydrothermal reactions carried out on cooper ions and H₃Salp. The results show that little ligands once again act as a coordination agent and have noticeable influence on both the structure and the magnetic properties of products. 5. Different products were obtained by changing the pH value of the hydrothermal reaction carried out on nickle ions and H₃Salp. The results show that hexanuclear nickel cluster may be obtained only when the pH value is between 5.5 to 6.5, otherwise trinuclear cluster was got.