Synthesis,self-assembly And Magnetic Properties Of Transition Metal Clusters

With the development of science and technology,magnetic materials play a more and more important role in our daily life and national economy,such as electromagnetic cooker,nuclear magnetic resonance,maglev train,computer memory and so on.With the fine development of industry,especially the demand for maximum storage in computer information storage,the pursuit of magnetic materials of smaller size is higher.This will promote the development of magnetic materials to molecular-based magnetic materials to a certain extent.Single molecule magnet（SMMs）belongs to nanometer magnetic material,its magnetism depends on the interaction with the spin ground state and magnetic anisotropy of the cluster itself,while the magnetism of the traditional magnet is the result of the interaction between atoms or molecules.Therefore,SMMs has the following typical magnetic properties:（1）below the critical temperature,it shows a phenomenon similar to the magnetic lag of the traditional magnet,that is,when the applied magnetic field is removed below the critical temperature,the magnetic attenuation is very slow;（2）the intermolecular interaction is weak and can be approximated to zero-dimensional system.Since the emergence of the first compound with the properties of SMMs,many compounds with the behavior of SMMs have been synthesized.Manganese clusters containing trivalent manganese are the most common in transition SMMs.However,in order to obtain compounds with novel structure and better magnetic properties,people have also begun to switch to other transition metal ions,such as iron,cobalt,nickel and so on.In addition to metal ions,ligands also have an important influence on the topological structure and properties of compounds.However,the coordination modes of many ligands are known to be single,and the structure and magnetism of the resulting compounds will be relatively limited,so we focus on the synthesis of ligands with new structures,so we expect to get novel structures.A coordination compound with good magnetic properties.The first chapter of this paper is the introduction,which briefly introduces the classification of material magnetism,the concept and research progress of SMMs,single chain magnet,single ion magnet,the synthesis strategy of SMMs and the purpose of this paper.Meaning and main content.In the second chapter,we mainly introduce the method of fusion ligands to obtain two new ligands:the coordination mode of binding Pyridin-2-ylmethanols（hmp）and 1,3-diol.The ligand4-chloro-2-（hydroxy（pyridin-2-yl）methyl）phenol（H₂L₁）was synthesized.The ligand（5-Chloro-2-hydroxy-phenyl）-pyridin-2-yl-methanone oxime（H₂L₂）was synthesized by combining the coordination mode of pyridine oxime and phenoxime.Three kinds of transition metal clusters were obtained by different synthesis methods:{Fe^III[Fe^III（L₁）₂]₃}（1）、[Mn₄^IIIMn₂^II（L₂）₄（HL₂）₂（μ₃-O）₂（CH₃OH）₄（Cl）₂]（2）、[Ni₉^II（L₂）₄（PhCOO）₈（CH₃OH）₆（μ₃-OH）₂]（3）.The crystal structure,magnetic properties and the effect of structure on magnetic properties of these compounds were analyzed.In the third chapter,the characteristics and advantages of polyhydroxyl ligands are introduced.On this basis,we synthesized the pentaol ligand 2,6(hydroxy-（2-hydroxy-phenyl）-methyl]-4-methyl-phenol（H₅L₃）,which has greater coordination potential.Two metal clusters were obtained by different synthesis methods:[Mn₄^IIIMn₂^II（L₃）₂（HL₃）₂（CH₃OH）₄]（4）、[Co₄^II（L₃’）₂（CH₃OH）₂（Cl）₂（5）[the ligands in compound 5 changed in the reaction:the two alcohol hydroxyl groups of the ligand H₅L₃ reacted with two methanol to form ether bonds,respectively.A new ligand2,6-Bis-[（2-hydroxy-phenyl）-methoxy-methyl]-4-methyl-phenol（H₃L₃’）]was formed,and their crystal structure,magnetic properties and their effects on magnetic properties were analyzed.In the fourth chapter,the significance of the work of this paper is described,and the structure,magnetism and the influence of the structure on the magnetic properties of the clusters are summarized.