The Study Of Synthesis, Crystal Structure And Characterization Of New Complexes Based On Keggin-Polyoxometalate Building Units

The aim of this thesis is the synthesis of new polyoxometalate compounds on the basis of Keggin type polyoxoanion clusters, which are decorated or bridged by various transition metal compounds. The study on synthetic conditions and rules for these new compounds and the exploration of relationships between structures and properties for these new compounds are also carried out.Four new polyoxometalate compounds have been synthesized on the basis of hydrothermal technique methods and structurally characterized by elemental analyses, IR, XPS, TG and single crystal X-ray diffractions. The thermal stabilities, magnetic properties and electrochemical behavior of these compounds have been studied.Compound 1 is an unusual bicapped bisupporting POM: [{Co(2,2'–bipy)₂(H₂O)}₂] [PMo₇^VIMo₅^VO₄₀(V^IVO)₂]. Compound 1 is composed of bicapped pseudo-keggin [PMo₇^VI- Mo₅^VO₄₀(V^IVO)₂]^4- unit and two {Co(2,2'-bipy)2(H₂O)} fragments. Each [PMo₁₂V2O42] unit acts as a ligand covalently bonded to two {Co(2,2'-bipy)₂(H₂O)} subunits through the terminal oxygen atoms of the two capping V atoms.Compound of 2 is a bisupporting POM: [{Ni(phen)₂(H₂O)}₂](H₃O)[PMo₁₀^VI Mo₂^VO₄₀]·4H₂O. It consists of a keggin polyoxoanion [PMo₁₂O₄₀]^5-, two {Ni(phen)₂(H₂O)} fragments, one protonated water and four lattice water molecules. Two {Ni(phen)₂(H₂O)} fragments are supported on two molybdenum atoms via two terminal oxygen atoms on two opposite {MoO6} faces of the keggin polyoxoanion.The structure of 3 is constructed from the cationic 2D sheets, [PMo₈^VIMo₄^VO₄₀- (V^IVO)₂{Co(phen)₂}₂]⁺, pillared by bicapped bisupporting [PMo₄^VIMo₈^VO₄₀(V^IVO)₂{Co- (phen)₂(H₂O)}₂]^3- heteropolyoxo anion into a 3D supramolecular framework. the cationic 2D sheet [PMo₈^VIMo₄^VO₄₀(V^IVO)₂{Co(phen)₂}₂]⁺ is formed, which is built from the [PMo₈^VIMo₄^VO₄₀(V^IVO)₂] cluster units linked from the[Co(2)(phen)₂] coordination complexed. The magnetic property for compound 3 was studied and antiferromagnetic interactions exist in compound 3.The structure of 4 [{Mn(bpy)(py)(H₂O)₂}{Mo₁₂O₃₄(bpy)₁₂}][PMo₁₂O₄₀]₂·2H₂O is double keggin-ions serve as templates so that hybrid cationic building blocks are aggregated around them , leading to the assembly of a large-porous supramolecular network. Such a porous host assembled with double Keggin-ion templates has never been observed so far. The electrochemical behavior of compound 4 was investigated. It displays good electrocatalytic activity.