Syntheses,Structures And Magnetic Properties Of Lanthanide And Lanthanide-transition Metal Clusters Based On Lacunary Polyoxometalate

Lanthanide and lanthanide-transition metal complexes are one of the most active research aspects in the field of inorganic chemistry and materials chemistry,not only because of their aesthetically pleasing molecular structures,but also because of their interesting luminescent,electronic,magnetic,and catalytic properties.Particularly,with the rapid development of the information technology,the potential applications in information storage and quantum computing of lanthanide and lanthanide-transition metal complexes have been paid attention by some scientific researchers.At present,the main synthesis method of polynuclear lanthanide and lanthanide-transition metal complexes reported in literatures is to select the appropriate organic ligands and control the reaction at a higher pH value.However,the addition of organic ligands,resulting in the stabilities of such metal clusters getting worse and hindering the expolration of some properties.Therefore,it is still a great challenge to explore the synthesis methods of high-nuclearity metal clusters with specific structures and properties.By Literature researching,we found that the lacunary polyoxometalate with better nucleophilicity and stability can be used as an ideal multidentate inorganic ligand to synthesize lanthanide and lanthanide-transition metal complexes.Based on the research background,we chose the trivacant[SbW9O33]9-multidentate ligand to design and synthesize lanthanide and lanthanide-transition metal clusters by regulating the pH values,ionic strength and anionic templates.The main contents are divided into three parts:1.Syntheses,structures and magnetic properties of lanthanide metal complexes based on pH values.A series of lanthanide metal complexes(1-6)with different structures were synthesized by adjusting the pH values of NaAc/HAc solution based on the trivacant[Sb9O33]9-ligand.The crystal structure analysis shows that the pH value has an important influence on the stability of the[SbW9O33]9-and the structures of lanthanide metal complexes.The magnetic studies indicate that the compound 1 and 4 have a slow relaxation magnetization on the appearance of out-of-phase.The ac susceptibility measurements show that the in-phase(?')and out-of-phase(?")signals of compound 1 give a clear frequency-dependent,and the out-of-phase signals have apparent peaks.2.Syntheses,structures and magnetic properties of lanthanide metal complexes based on ionic strength.On the basis of the previous chapter,we chose the pH=5.5 NaAc-HAc buffer as a solvent and obtained a series of lanthanide-transition metal clusters(7-9),lanthanide metal clusters(10-12)and transition metal cluster(13)with different structures by adjusting the ionic strength of solution.The crystal structure analysis shows that the ionic strength has a significant impact on the coordination ability with metallic ion and the topological structures of clusters.In ac susceptibility measurements,the slow relaxation of magnetization is observed in 7 and 10 based on the appearance of out-of-phase signals(?").3.Syntheses,structures and magnetic properties of lanthanide metal complexes based on ionic templates.On the basis of the previous chapter,we attempted to introduce different anions CO32-,PO43-and[Mo8O26]4-as the templates to the reaction system and successfully obtained a series of lanthanide-transition metal clusters(14-21)and one lanthanide metal cluster(22)with different structures.Due to the introduction of the PO43-,the precursor {SbW9O33} formed the new trilacunary Keggin-type unit{PW9O34} in situ reaction,and one Ln3+ and three Ni2+ connect with each other through three ?3-OH and one O atom,forming a heterometallic 3d-4f cubane-like{LnNi3(?3-OH)3(?4-O)} unit in the compounds 20 and 21.Three trilacunary a-Keggin units {B-?-PW9O33},two trilacunary ?-Keggin units {B-?-SbW9O33} and three cubane-like units {LnNi3(u3-OH)3(?4-O)} are connect together by three bridged carboxyl from the acetate ligands,forming a new kind of lanthanide-transition metal clusters.This is the first lanthanide-transition metal cluster containing two kinds of different trilacunary POMs.The crystal structure analysis shows that the anionic template plays an important role in controlling the structures of clusters and can effectively increase the number of metal ions,succeeding in controlling the structure assembly of lanthanide-transition metal clusters.