Syntheses,Structures And Magnetic Properties Of Lanthanide-Transition Metal Clusters Based On Carboxylic Acid Mixed Ligands

The rare earth-transition metal cluster not only because of its charming structure,but also because of its rich optical,electrical,magnetic and catalytic properties,it has become one of the research focuses in the field of Inorganic Chemistry and Material Chemistry.However,it is still a great challenge to design and synthesize rare earth-transition metal clusters with specific structures and properties.In this thesis,we adopt iminodiacetic acid as the main ligand,the acetate,propionate and amino acid as the auxiliary ligands to synthesize series of 3d-4f clusters with unique structures throngh mixed-ligand approach and study their structure and magnetic properties.The concrete contents are as follows:1.We chose iminodiacetic acid as the main ligand,acetate as the auxiliary ligand,the CO32-which is from Na2CO3 as the ionic template to obtain four isomorphic Ln44Ni28 clusters(1-4).The crystal structure analysis suggests that CO32-plays an important role in constructing the clusters.Through the coordination atom O of the CO32-,the heart-shaped {Dy11Ni7? unit is connected to form a huge ring structure with four times symmetry.Using propionate instead of acetate,we also get the same structural ring cluster(5)by changing the ratio of the reactants.The magnetic studies indicate that Gd44Ni28 exhibits large magnetocaloric effect.2.On the basis of the synthesis of the cyclic Ln44Ni28 clusters,through increasing the content of acetate but not adding Na2CO3,we synthesized the ring Dy50Ni40 cluster(6).The analysis of crystal structure shows that the heart-shaped {DyioNi8} unit is connected to form a giant ring cluster with five times symmetry through the briging role of CH3COO-.CH3COO-compared with CO32-,due to the steric hindrance effect of methyl group,the Dy50Ni40 cluster with higher nuclear number than Ln44Ni28 are fomed.Magnetic study indicates that Dy50Ni40 has obvious frequency dependence.3.On the basis of the synthesis of the Ln44Ni28 and Ln50Ni40 clusters,we adopt amino acids with larger steric hindrance as the the auxiliary ligand to get LnsNii2 clusters(7-9)with double shell structure.We do not obtain larger nuclear number clusters which may due to the amino acid auxiliary ligand that is the same as iminodiacetic acid ligand contains O and N and coordination atoms to lead two ligands has competitive reaction for metal ions.Compared with the acetate auxiliary ligand,the size of the auxiliary ligand and types will influence the shape and size of clusters.By changing the proportion of the reactants,the same structure cluster(9)could also be obtained when the chiral proline was replaced by chiral alanine.