Synthesis And Properties Of Co/Ni/Cu Complexes With Pyridine/Pyrazine Derivatives As Main Ligands And Polyoxometalate/Polycarboxylates As Coligands

In this paper,nine transition metal–organic complexes（MOCs）based on the N-heterocyclic organic ligands[pyridyl-amide,pyrazin-bis（triazole）,pyrazin-triazole-tetrazole and bis（pyridyl）-bis（amide）]as the main ligands,and Anderson-type polyoxometalate/isopolymolybdates anions coligands were designed and synthesized successfully under hydrothermal or solvothermal technologies.The structurally characterized by single-crystal X-ray diffraction,powder X-ray diffraction（PXRD）and IR spectra.The adsorption and photocatalytic behaviors for organic dyes and electrochemical properties of some title MOCs were investigated in detail.1.The pyrazine-polyazole,pyridyl-amide/tetrazole were selected as theN-heterocyclic organic ligands,and Anderson-type polyanions or [γ-Mo₈O₂₆]^4-anions was used as the inorganic building unit to assemble with different transition metal ions under hydrothermal or solvothermal conditions.Eventually six functional metal–organic complexes were obtained.It is worth mentioning that the[γ-Mo₈O₂₆]^4-isopolyanion in complex 3 is transformed by in situ Anderson-type[IMo₆O₂₄]^5-anion during the reaction.The ligand HTrz in complex 5 was converted in situ from the starting ligand TAAP during the reaction.{Ni₃（Hpytty）₂[AlMo₆（OH）₅O₁₉]（H₂O）₄（CH₃O）（1）{Ni₃（Hpytty）₂[CrMo₆（OH）₅O₁₉]（H₂O）₁₀}·6H₂O（2）{Co₂（pytty）[γ-Mo₈O₂₆]_0.5（H₂O）₅}·4H₂O（3）{Cu₂（Hpytytz）[CrMo₆（OH）₅O₁₉]（H₂O）₄}·3H₂O（4）{H₂Cu₁₂（Trz）₁₂[CrMo₆（OH）₆O₁₈]₂（OH）₈（H₂O）₄}·12H₂O（5）Cu₄（2-pdya）₂(AlMo₆（OH）₅O₁₉)₂（H₂O）₄·7H₂O（6）H₂pytty=3-（pyrazine-2-yl）-5-（1H-1,2,4-triazol-3-yl）-1,2,4-triazolylH₂typtz=3-（tetrazol-5-yl）-5-（pyrid-3-yl）-1,2,4-triazolylTAAP=3-（1H-Tetrazole-1-acetic acid amido）pyridineHTrz=1H-Tetrazole2-pdya=2-pyridine-pyrazinamideComplexes 1-3 were obtained with the H₂pytty ligand under solvothermal conditions.Among them,complexes 1 and 2 have similar crystallography parameters and both of them possess the 0D structure.Then their 1D supramolecular chain structures are formed by the weak hydrogen bonding interactions between the AlMo₆/CrMo₆ polyanions and protonated Hpytty ligands.In complex 3,showing a 3D structure frame through linking the adjacent 2D Co-pytty metal organic layer by theγ-Mo₈ anion.Complexes4 and 5 are obtained under hydrothermal conditions.Complex 4 is a 1D chain formed by[Cu₄（Htypytz）₂]²⁺unit connecting two CrMo₆ polyanions.While 5is a two-dimensional metal-organic layer formed by Trz ligand and Cu²⁺ions.The terminal oxygen atoms of the[CrMo₆（OH）₆O₁₈]^3-polyoxoanions is connected to the Cu²⁺ions to further form a three-dimensional coordination framework,which is worth noting that the TAAP ligand is converted in situ to Trz during the synthesis.The 2D supramolecular layered structure of complex6 was obtained under solvothermal conditions,which was formed by connecting two adjacent 1D chains.The structural diversities of the complexes in this chapter show that the organic ligands,solvents,and polyoxometalate in the system play vital roles in constructing the final structures of the complexes.2.By introducing the bis（pyridyl）-bis（amide）ligand into three kinds of aromatic dicarboxylates-transition metal systems,three functional complexes were successfully obtained under solvothermal conditions.Co（3-ebpab）（TPA）·H₂O（7）Co（3-ebpab）（5-CH₃-TPA）·H₂O（8）Co（3-ebpab）（5-NH₂-TPA）·H₂O（9）[3-ebpab=（E）-4,4’-（ethene-1,2-diyl）bis（N-pyridin-3-yl）benzamide);TPA=Terephthalic acid;5-CH₃-Terephthalic acid;5-NH₂-TPA=5-NH₂-Terephthalic acid]Single crystal X-ray diffraction analysis shows that complexes 7,8 and 9have similar crystal parameters.Except for the differences in the auxiliary carboxylic acids,their structures are similar 2D layer structures.By connecting two types of 1D chains through the central metals to form a 2D layer The photocatalytic performance of the complexes on organic dyes was also studied.