Design,Syntheses And Properties Of Polyoxometalate-based Metal–organic Complexes Based On Bis(Pyrazine)-Bis(Amide) Ligands

In this paper,fifteen new complexes based on Anderson/Keggin/octamolybdate type anions and pyrazinamide derivatives organic ligands were prepared successfully by using hydrothermal synthesis technology.The crystal architectures were characterized by utilizing single-crystal X-ray diffraction analyses,IR spectra and powder X-ray diffraction(PXRD).Furthermore,the dye adsorption ability and the electrochemical performance of the complexes were also probed.1.Two flexible bis(pyrazine)-bis(amide)ligands [bpae = N,N?-bis(2-pyrazinecarboxamide)-1,2-ethane,bpab = N,N?-bis(2-pyrazinecarboxamide)-1,4-butane]were selected to combine Cu^? ions and Anderson/Keggin/octamolybdate-type polyoxometalate(POM)-based complexes(MOCs)under the hydrothermal conditions.Eight new POM-based MOCs were constructed successfully.{HCu(bpae)[CrMo₆(OH)₆O₁₈]}·4H₂O(1){HCu(bpae)[AlMo₆(OH)₆O₁₈]}·4H₂O(2)[Cu₃(bpae)_0.5(TeMo₆O₂₄)(H₂O)₉](3)[Cu₂(bpae)₂(H₂O)₂(P Mo₉^?Mo₃^VO₃₉)](4)[Cu₂(bpae)₂(SiMo₁₂O₄₀)]·2H₂O(5)[Cu₂(bpae)₂(?-Mo₈O₂₆)]·6H₂O(6){HCu(bpab)(H₂O)₂[AlMo₆(OH)₆O_{1 8}]}·4H₂O(7){H₂Cu(bpab)(?-Mo₈O₂₆)(H₂O)₂}·2H₂O(8)Complexes 1-2 are isostructural and are based on the B-type Anderson-type anions.The [CrMo₆(OH)-6O₁₈]^3-(CrMo₆)anions are selected in 1,while the [AlMo₆(OH)₆O₁₈]^3-(AlMo₆)anions are employed in 2.Complexes 1-2 are 2D networks based on the bidentate bridging Anderson anions(CrMo₆/AlMo₆)and the ?2-bridging bpae ligands.Complex 3displays an unusual 3,4,4,5-connected complicated 3D topological network derived from the tetradentate bridging A-type Anderson anions [Te Mo₆O₂₄]^6-(Te Mo₆) and the ?4-bridging bpae ligands.Complex 4 is a [PMo₉^VIMo₃^VO₃₉]^4-(PMo₁₂)-based 3D coordination framework,which is constructed by three kinds of 1D chains: [Cu(bpae)]_n²ⁿ⁺,[PMo₁₂]_n^4n-and [Cu(PMo₁₂)]_n^2n- chains.Complex 5 shows a 2D structure,which is composed of the tridentate [SiMo₁₂O₄₀]^4-anions(Si Mo₁₂)and the [Cu(bpae)]_n²ⁿ⁺ chains.Complex 6possesses a 3,4,4-connected 3D topological structure,containing bidentate coordinated [?-Mo₈O₂₆]^4-(Mo₈) anions and the ?₃-bridging bpae ligands.Complex 7 is a 2D supramolecular architecture consists of the AlMo₆ anions and the metal-organic chains[Cu(bpab)]_n²ⁿ⁺ via hydrogen bonds.Complex 8 manifests a 2D supramolecular network,in which the Mo₈ anions act as non-coordinating templates.The results demonstrate that the spacer length of the ligands and POM anions exhibited an important effect on modifying the final structures.Complexes 1-8 have remarkable dye adsorption capacity for MB and GV,and 1 has ability to rapidly adsorb and selectively separate cationic dyes.3,4 and 6 have outstanding electrochemical activity.6 can also be used as an amperometric sensor to detect Cr(?),Fe(?),BrO₃^- and NO₂^-.2.Methyl substituted bis(pyrazine)-bis(amide)ligands [bmpae = N,N?-bis(5-methyl-2-pyrazinecarboxamide)-1,2-ethane,bmpap = N,N?-bis(5-methyl-2-pyrazinecarboxamide)-1,3-propane,bmpab = N,N'-bis(5-methyl-2-pyrazinecarboxamide)-1,4-butane] were chosen as the organic ligands to combine Co/Cu transition metal ions with different coordination characteristics and /Keggin/octamolybdate-type POMs.Five new POM-based MOCs were constructed successfully under the hydrothermal conditions.{[Co₂(bmpae)₂(H₂O)₄](SiW₁₂O₄₀)}·4 H₂O(9)[Cu₂(bmpae)₂(SiW₁₂O₄₀)]·8 H₂O(10)[Cu(bmpae)_0.5(Mo₃O₁₀)(H₂O)]·H₂O(11)[Cu₂(bmpap)(?-Mo₈O₂₆)(H₂O)₄]·3H₂O(12){H₂Cu(bmpab)(?-Mo₈O₂₆)(H₂O)₂}·2H₂O(13)Complex 9 is a 0D structure,which exhibits discrete [SiW₁₂O₄₀]^4-(SiW₁₂) anions.In10,the 1D [Cu(bmpae)]_n²ⁿ⁺ chains are connected by the SiW₁₂ anions to produce a 2D structure.Complex 11 is a 3D famework containing the 2D Cu(bmpae)0.5]n2n+ metalorganic layers and the 1D inorganic [Mo₃O₁₀]_n^2n-chains.Complex 12 displays a 2D network structure consisting of bidentate coordinated Mo₈ anions and ?₄-bridging bmpap ligands.Complex 13 manifests a 2D supramolecular network,in which the Mo₈ anions act as non-coordinating templates.The influences of central metal ions and spacer lengths of ligands on the architectures of the target complexes are discussed.Complexes 9-13 have significant electrochemical activity on the reduction of hydrogen peroxide and potassium bromate,and 10-13 show good adsorption behavior towards MB and GV.3 The semi-rigid bis(pyrazine)-bis(amide)ligand [bpac=N,N'-bis(2-pyrazinecarboxamide)-1,2-cyclohexane] was used as the organic ligand,finally two metalorganic complexes based on Keggin-type anions or octamolybdate anions were obtained by adjusting the type of POM anions.By introducing a semi-rigid ligand [bpac = N,N?-bis(2-pyrazinecarboxamide)-1,2-cyclohexane] into the POMs systems,two POM-based MOCs were constructed successfully under the hydrothermal conditions.[Cu₂(bpac)₂(SiW₁₂O₄₀)](14)[Cu(bpac)(?-Mo₈O₂₆)_0.5]·H₂O(15)Crystal analysis reveals that complex 14 is a 2D supramolecular structure based on the1 D [Cu(bpac)]_n²ⁿ⁺ chains,in which the [SiW₁₂O₄₀]^4-(SiW₁₂)anions serve as noncoordinated templates.Complex 15 is a 2D network,which is composed of the bidentate bridging [?-Mo₈O₂₆]^4-(Mo₈)anions and 1D [Cu(bpac)]_n²ⁿ⁺ chains.The different POM anions have an important influence on the structures of the complexes.Both 14-15 display excellent adsorption behavior and can effectively adsorb organic dyes methylene blue and gentian violet.In addition,the bifunctional electrocatalytic performance of 14-15 were also studied.