Polyoxometalate-based Metal-organic (Supramolecular) Complexes Constructed From Semi-rigid Polyazole Ligands:Synthesis,Structure And Properties

Here,eleven polyoxometalate（POM）-based complexes have been synthesized by using semi-rigid polyazole derivatives as organic ligands under hydrothermal or solvothermal conditions,which have been characterized by single crystal X-ray diffractions,PXRD,IR and TG,et al.The influences on the final structures of the compounds of ligand configurations,reaction conditions and POMs were also investigated.Further,the electrochemical properties and photocatalytic activities toward the degradation of organic dyes were studied.1.The combination of semi-rigid bis-benzotriazole derivatives,Cu²⁺ion,POM anions（Anderson or Lindqvist type）,gave two POM-based complexes（1-2）.Cu（L¹）[CrMo₆（OH）₆O₁₈]·5（CH₃CH₂OH）·7H₂O（1）[Cu（L²）₂(Mo₆O₁₉)]（2）L¹=1,4-bis（1-H-benzotriazolyl-oxo-methyl）phenylL²=4,4’-bis（1-H-benzotriazolyl-oxo-methyl）biphenylA kind of POM-based inorganic chain is constructed from Cu²⁺ions and[CrMo₆O₂₄]^6-anions in compound 1,which is extended further into a 3D framework structure by L¹ ligands.Compound 2 show a“3D+3D”two-fold interpenetrating framework based on Lindqvist-type POM.The structural analysis reveals that the steric hindrance of POM may play a key role in inducing the diverse framework structures.Compound 1 displays not only good adsorption activities toward crystal violet（CV）,but also perfect selective adsorption properties for methylene blue（MB）.Compound 2 shows a good photocatalytic activity toward the degradation of organic dyes,including Rhodamine B（RhB）and MB.2.By changing the substituted groups and length of the semi-rigid bis-benzotriazole ligands,five complexes（3-7）based on different POMs and metal ions have been obtained under different reaction conditions.[Cu^I（L⁴）][Cu^I(β-Mo₈O₂₆)_0.5（L⁴）]（3）H₃（L⁴）₂(PMo₁₂O₄₀)·2CH₃CH₂OH（4）H₃（L³）₂(PMo₁₂O₄₀)（5）H₃（L⁵）₃(PMo₁₂O₄₀)（6）[Ag（L⁵）](H₃PW₁₂O₄₀)（7）L³=1,4’-bis（imidazolyl-1-methyl）phenylL⁴=1,4’-bis（benzimidazolyl-1-methyl）phenylL⁵=1,4’-bis（imidazolyl-1-methyl）biphenylCompound 3 consists of metal-organic belts[Cu^I(β-Mo₈O₂₆)_0.5（L⁴）]^-and metal-organic chains[Cu^I（L⁴）]⁺,and the former is threaded by the latter to give a3D framework structure.Compounds 4-7 exhibit supramolecular structures,where the weak interactions between C-H,N and O atoms play important roles in the formation of final structures.Compound 3 displays bi-functional electrocatalytic behaviors for the oxidation of ascorbic acid（AA）,the reduction of nitrite and hydrogen peroxide.Compounds 4,6 and 7 have good photocatalytic activities toward the degradation of RhB,MB and CV,respectively.3.By introducing the new semi-rigid bis-thionazole ligands into the reaction systems containing different POMs,four complexes（8-11）have been synthesized under hydrothermal condition in the presentence of Ag⁺ion.Ag₂（L⁶）(HPW₁₂O₄₀)（8）Ag₂(L^6-1)(L^6-2)(H₃PMo₁₂O₄₀)（9）Ag₄(L^7-1)₄(H₃PW₁₂O₄₀)（10）Ag₄(L^7-1)₄(H₃PMo₁₂O₄₀)（11）L⁶=1,4’-bis（5-thionazolyl-1-methyl）phenyl L⁷=1,4’-bis（5-thionazolyl-1-methyl）biphenyl L^6-1=4-（5-thionazolyl-1-methyl）benzoic acid L^6-2=1-methyl-tetrazoleL^7-1=4-（5-thionazolyl-1-methyl）biphenylcarboxylic acidIn compounds 8-11,the Ag-S bonds show key roles in the formation of all structures,besides the Ag-N and Ag-O bonds.Compound 8 is a 3D framework structure,which is formed by L⁶/Ag 2D layers and[PW₁₂O₄₀]^3-anions.There are two kinds of ligands in 9,L⁶-1-1 and L^6-2,which are obtained from the transformation in situ of L⁶ ligand,respectively.The isostructural 10 and 11 have supramolecular structures,in which the L⁷-1-1 ligand is provided by the transformation in situ of L⁷ligand.The Ag-S,Ag-O bonds and the weak interaction of O···O show important roles in the formations of the structures.Compounds 8-11 show not only electrocatalytic cativities for the reduction of nitrite and hydrogen peroxide,but also photocatalytic activities toward the degradation of different organic dyes.