Synthese, Structure, And Property Study Of Polyoxometalate Crystals Assembled By Supramolecular Interaction

In this thesis, a new series of polyoxometalate supramolecular assembly based on organic amines, macrocations, metal compounds and polyoxometalates (POMs) have been synthesized via coordination bonds and supramolecular interaction. 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.Twelve new polyoxometalate compounds have been synthesized on the basis of hydrothermal technique or convenient aqueous solution synthesis methods and structurally characterized by elemental analyses, IR, Diffuse-reflectance UV/Vis spectrum, TG and single crystal X-ray diffractions. The thermal stabilities, magnetic properties and electrochemical properties of these compounds have been studied.1. Six supramolecular intercluster compounds on the basis of Keggin and Dawson type polyoxoanion cluster and macrocation have been synthesized by convenient aqueous solution method and structurally characterized: KH₂[Cr₃O(OOCCH₃)₆(H₂O)₃][α-SiMo₁₂O₄₀]·11H₂O (1) KH₂[Cr₃O(OOCCH₃)₆ (H₂O)₃][α-SiW₁₂O₄₀]·11H₂O (2) K₂[Cr₃O (OOCCH₃)₆ (H₂O)₃] [α-PW₁₂O₄₀]·17H₂O (3) Na[Cr₃O(OOCCH₃)₆ (H₂O)₃]₂ [α-PMo₁₂O₄₀]·12H₂O (4) K₂NaH [Cr₃O(OOCCH₃)₆ (H₂O)₃] [α-CoW₁₂O₄₀]·10H₂O (5) H₅[Cr₃O(OOCCH₃)₆ (H₂O)₃] [α-P₂Mo₁₈O₆₂]·10H₂O (6)The polyanions and macrocations stacked alternately through hydrogen bonds, electrostatic interactions and coordination bonds of K⁺ and Na⁺ to constitute a series of novel porous microstructure. In the crystal structures of 1, 2, 3 and 4, oppositely charged cluster ions stacked alternately to form three-dimensional framewok containing one-dimensional channels. Compound 4 and 6 exhibits compact packing pattern: In compound 4, six macrocation pillars packed along a-axis to form a straight 1D channel, in which accommodates a polyoxometalate pillar. In compound 6, six polyoxometalate pillars stacked on top of each other along a-axis to form a straight 1D channel, which houses a macrocation pillar. We discover that coutercation, the structure of trinuclear chromium cluster and the type of polyoxometalate cluster and stoichiometry of macrocation to polyoxomentalate are all important factors to influence the cluster packing style. The magnetic investigation on compound 1 and 5 shows a typical antiferromagnetic interaction.2. Two unique supramolecular compounds have been hydrothermally synthesized on the basis of polyxoxmetalate and flexile ligand: (NH₄)₂(H₂bpp)₂[Mo₇O₂₄]·8H₂O (7) (H₂bpp)₃ [Mo₅P₂O₂₃]·H₂O (8)Compound 7 represents a novel 3-D extended supramolecular"host"networks with 1-D channels encapsulating flexible cation"guests". The bpp molecular folds to provide a clothespin ligand geometry because of its good flexibility, which results in the organic bicapped structure. In compound 8, a twofold interpenetrating 3D supramolecular architecture has been constructed of Standberg type polyoxometalate and bpp molecular through the hydrogen bonds as well as electrostatic interactions. The two inoganic-organic hybrid materials were hydrothermally prepared and insoluble in water and common organic solvent, so they can be used as a chemically bulk-modified carbon paste electrode. The electrochemical properties of polyoxometalate was retained.3. An inoganic-organic composite compound constructed by the Keggin type polyoxoanions and rare earth coordination cations has been synthesized by convenient aqueous solution method. [Ce(DMSO)₈][PMo₁₂O₄₀] (9)Compound 9 represents an interesting two-dimensional supramolecular network constructed by polyoxoanions and rare earth coordination cations via hydrogen-bonding and van der Waals interactions. IR and single crystal X-ray diffractions indicated that there is strong supramolecular interaction between polyoxoanions and rare earth coordination cations.4. Three novel extended structural polyoxomelate compounds have been hydrothermally synthesized on the basis of flexile ligand bpp and rigid ligand 4,4′-bpy, which are brigded by transtion metal compounds. [Zn(bpp)V₂O₆] (10) [Cu₄(bpp)₄V₄O₁₂]·3H₂O (11) Cu(4,4′-bpy)[Mo₃VO₁₂] (12)Compound 10 represents the first chiral three-dimensional complex containing of infinite left-handed helical chains. Flexibility of the bpp ligand is essential for the formation of the helix. Compound 11 represents a new eight-connected self-catenated coordination net in which bimetallic {Cu₄V₄O₁₂} clusters act as eight-connected nodes for the first time. The successful isolation of this species not only provides an intriguing example of chemical topology but also confirms the feasibility of constructing highly-conneced heterometallic topology net from polyoxometalate clusters. Compound 12 exhibits a three-dimensional gridded network constructed by one-dimensional molybdete-vanadate strip.