The Synthesis, Structure And Properties Of POM Compounds Decorated By D¹⁰ Metal-rigid Organic Subunits

In this paper, the d¹⁰ metal ions Ag^I and Cu^I and a series of rigid organic ligand have been used. Thirteen POM-based multiple functional compounds have been obtained under hydrothermal conditions and characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. The electrochemical, photocatalytic and fluorescent properties of some compounds were investigated. The influence factors of varieties of POMs, reactants and kinds of ligands on the final structures have been further studied.1. By choosing 1-Amino-4-（3,5-dimethylpyrazolyl）hydralazine as organic ligands to modify classical Keggin anions as inorganic building units, three new POM compounds have been synthesized. The influence factors of difference of reactants on the final structures have been investigated.[Ag₃L₄（H₂O）₄][PMo₁₂O₄₀]·3H₂O（1）[Ag₃L₄（H₂O）₄][PW₁₂O₄₀]·2H₂O（2）[Ag₃L₆][PMo₁₂O₄₀]（3）（L=1-Amino-4-（3,5-dimethylpyrazolyl）hydralazine）Compound 1 contain two kinds of chain: The dinuclear Ag clusters are linked by Keggin anions through Ag-O band to construct a 1D chain, whereas the mononuclear Ag subunits form another supramolecular chain. The adjacent 1D coordination chains and supramolecular chains connect with each other through hydrogen bonding interactions to form a 2D supramolecular layer. Compounds 2 and 1 are isostructural. Under similar synthetic conditions, the difference of reactants, which result in obviously different structures of 1-3. In compound 3, the discrete mononuclear subunits [Ag L²]+ are linked by PMo₁₂O₄₀3– anions through hydrogen bonding interactions to construct a supramolecular chain.2. By using rigid imidazole derivative as organic ligands（2,2’-biimidazole, 5-butyl-2,2’-biimidazole, 1H-imdazole-2-carboxylic acid, 1H,1’H-biimdazole-4,4’-dicarboxylic acid） and the d¹⁰ transition metal ions to modify Keggin and Strandberg anions, five new POM compounds have been synthesized.[Ag₄（biz）₄][H₂P₂Mo₅O₂₃]·2H₂O（4）[Ag₄（bbiz）₄][HPWVI10W2^VO40]·2H₂O（5）（biz=2,2’-biimidazole,bbiz=5-butyl-2,2’-biimidazole）[Ag₂（L¹）₄][HPMo₁₂O₄₀]·3H₂O（6）[Ag₂（L¹）₄][HPW₁₂O₄₀]·H₂O（7）[Cu^I₆Cl₄（L²）₆][H3PMo₁₂O₄₀]·2NO₃（8）（L¹= 1H-imdazole-2-carboxylic,L²= 1H,1’H-biimdazole-4,4’-dicarboxylic acid）For compounds 4-5, the different anions have influences on the structures. In compound 4, the P2Mo5 anion owns a smaller volume. Thus, in order to reduce the repulsions between bi-nuclear [（Ag₃）（Ag₄）（biz）2]2+ clusters, the P2Mo5 anion only offers two symmetrical terminal O atoms to link two bi-nuclear clusters. But the PW12 anion in 5 owing to big volume can link four bi-nuclear Ag^I clusters by providing four bridging O atoms. Compounds 6 and 7 are isostructural and they display a 2D supramolecular layer. In compound 8, there exist double Cl-capped tri-nuclear Cu^I clusters.3.Under hydrothermal conditions,through choosing Ag ions and rigid1,2,4-1H-triazole,1Htetrazole and 1Htetrazole derivative as organic ligands to modify classical[PMo₁₂O₄₀]3-,[PW₁₂O₄₀]3-and[Si Mo₁₂O₄₀]4-anions as inorganic building units,five high dimensional compounds have been obtained.[Ag₁₀（L¹）6（HL¹）2][HPMo2VMoVI10O₄₀]（9）[Ag₁₀（L²）8(H₂Si Mo₁₂O₄₀)]（10）（L¹=1,2,4-1H-triazole, L²=1Htetrazole）[K₂Ag15（L³）10（H₂O）₂][H(PMo₁₁^VIMoVO₄₀)2]（11）,[Ag₇（L³）₄（H₂O）₂][PW₁₂O₄₀]（12）[Ag₁₀（L₄）8（H₂O）][PW₁₂O₄₀]（13）（L³=5-o-tolyl-1H-tetrazole,L₄=5-m-tolyl-1H-tetrazole）Compound 9 exhibits a two dimensional metal-organic layer containing adjacent tetra-nuclear Ag cycles. Furthermore, the adjacent 2D layers are further extended by Ag6 ions to form a three dimensional channel-like framework, with Keggin anions embedding in the channels. Compound 10 is isostructural with 9. Compound 11 shows a 3D metal–organic framework. The inorganic chain in 11 with Keggin anions linked by Ag1 ions insert into the channels of this 3D MOF. In compound 12, the Ag belts are connected by Keggin anions to construct a 2D layer. Adjacent layers link with each other through Ag–O bonds and the 3D framework of 12 is thus built. In compound 13, the 2D Ag layer possesses Ag cycles. Adjacent layers are linked by Ag–N bonds and Keggin anions to form the 3D structure of 13.Furthermore, the electrochemical, photocatalytic and fluorescent properties of some compounds were investigated. The results show that some compounds own good electrochemical and photocatalytic properties, which will act as potential inorganic-organic hybrid functional materials.