Junjun Sun

A series of novel Anderson-type polyoxometalate-based MnII complexes constructed from pyridyl-derivatives: assembly, structures, electrochemical and photocatalytic properties

Three novel Anderson-type polyoxometalates (POMs)-based metal–organic complexes (MOCs), namely, [Mn2(4-pdtz)2[CrMo6(OH)5O19](H2O)4] (1), {Mn(3-dpye)0.5[CrMo6(OH)6O18](H2O)}·(3-H2dpye)0.5 (2), [Mn2(3-H2dpye)(TeMo6O24)(H2O)6]·4H2O (3) (4-pdtz = 4-pyridino-bistriazol, 3-dpye = N,N′-bis(3-pyridinecarboxamide)-1,2-ethane), were hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). In complex 1, the [CrMo6(OH)5O19]4− (CrMo6) polyoxoanions bridge the MnII ions to generate a 1D Mn–CrMo6 inorganic chain, on which the 4-pdtz ligands hang. In 2, the adjacent CrMo6 polyoxoanions are linked by MnII ions to form a 2D inorganic layer, which is further linked by 3-dpye forming a 3D metal–organic framework (POMOF). Interestingly, the large voids of the 3D POMOF accommodate free protonated 3-H2dpye molecules. In complex 3, the adjacent TeMo6O246− (TeMo6) polyoxoanions are linked by MnII ions to form a 1D inorganic chain, the protonated 3-H2dpye act as bidentate ligands connecting two MnII centers with the oxygen atoms from amide groups, forming a steady 2D metal organic layer. The effects of various coordination behaviors of the pyridyl-based ligands and central metal ions on the structures of the title complexes have been discussed. The title complexes exhibit excellent electrocatalytic activity towards the reduction of bromate and hydrogen peroxide. In addition, the redox potentials of complex 3 is highly sensitive to pH and may be used as a kind of potential pH sensor. The photocatalytic properties of the title complexes under UV and visible irradiation have been investigated in detail.

pH-tuned diverse structures and properties: two Anderson-type polyoxometalate-based metal–organic complexes for selective photocatalysis and adsorption of organic dyes

Two novel Anderson-type polyoxometalates (POMs)-based metal–organic complexes, namely, Cu5(μ2-OH)2(4-dpye)2[CrMo6(OH)5O19]2(H2O)10 (1), {Cu(4-Hdpye)[CrMo6(OH)6O18](H2O)2}·2H2O (2) (4-dpye = N,N′-bis(4-pyridinecarboxamide)-1,2-ethane), were hydrothermally synthesized in different pH ranges and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Complex 1 shows a 3D (3,4)-connected framework constructed by the 2D {Cu5(μ2-OH)2[CrMo6(OH)5O19]2} inorganic layer and bidentate 4-dpye bridging ligands. Complex 2 exhibits a 2D polymeric structure based on the 2D {Cu[CrMo6(OH)6O18](H2O)2} layer and monodentate 4-Hdpye ligands. The complexes 1 and 2 prove that the pH value plays an important role not only in the synthesis and structures but also for the properties of the title complexes. Their electrochemical behaviour and electrocatalytic activities towards the reduction of bromate and hydrogen peroxide have been reported. In addition, the selective photocatalytic properties and adsorption of organic dyes for 1 and 2 have been investigated. Complex 1 possesses good photocatalytic activity towards the degradation of organic dyes Congo Red (CR) and methylene blue (MB), while complex 2 has high adsorption capacity of MB/CR at room temperature. All MB/CR molecules adsorbed on 2 can be completely released in NaCl-containing DMF solution.

Self-assembly, structures and properties of three new Ni(II) coordination polymers derived from two different bis-pyridyl-bis-amide ligands and two aromatic polycarboxylates

AbstractThree new Ni(II) coordination polymers exhibiting different 1D and 2D framework structures have been hydrothermally synthesized: [Ni(L 1)(1,3-BDC)(H 2O) 3] ⋅H2O (1), [Ni(L 1)(1,3,5-HBTC)(H 2O) 3] (2), [Ni 3(L 2)3(1,3,5-BTC) 2(H 2O) 8] ⋅12H 2O (3) [L 1= N,N ′-bis(pyridin-3-yl)cyclohexane-1,4-dicarboxamide, L 2= N,N ′-bis(3-pyridyl)octandiamide, 1,3-H 2BDC = 1,3-benzenedicarboxylic acid, 1,3,5-H 3BTC = 1,3,5-benzenetricarboxylic acid]. X-ray single crystal diffraction analyses revealed that polymer 1 is a 2D interlaced layer based on the 1D [Ni(L 1)(1,3-BDC)(H 2O) 3] meso-helical chains. Polymer 2 is a 1D wave-shaped chain derived from the 1D [Ni(L 1)] n chain and monodentate coordinated 1,3,5-HBTC anions. Polymer 3 possesses an interesting 2D layer containing the trinuclear [Ni 3(1,3,5-BTC) 2] substructural unit and 1D zigzag [Ni(L 2)] n chain, representing a 3,4-connected {6 ⋅8 2} 2 {62⋅82⋅10⋅12} topology. Finally, the adjacent 1D chains or the 2D layers are connected through hydrogen bonding interactions to construct 3D supramolecular networks. Further, the thermal stability, solid state fluorescent property and photocatalytic activity of 1–3 have been investigated. Graphical AbstractThree new Ni(II) coordination polymers have been hydrothermally synthesized by self-assembly of two bis-pyridyl-bis-amide ligands (L1, L2) and two aromatic polycarboxylates (1,3-H2BDC, 1,3,5-H3BTC). The thermal stability, fluorescent properties and the photocatalytic activities of polymers 1–3 have been studied.

Hydrogen Bonding Interactions Directed Various Supramolecular Networks Based on Octamolybdates and Different Flexible Bis-Pyridyl-Bis-Amide Ligands

Four new inorganic–organic hybrid supramolecular architectures constructed from octamolybdates (Mo8O26) and different bis-pyridyl-bis-amide ligands, (3-dpye = N,N′-bis(3-pyridinecarboxamide)-1,2-ethane, 4-dpye = N,N′-bis(4-pyridinecarboxamide)-1,2-ethane, 3-dpyp = N,N′-bis(3-pyridinecarboxamide)-1,3-propane, 4-dpyp = N,N′-bis(4-pyridinecarboxamide)-1,3-propane): (3-H2dpye)(γ-Mo8O26)0.5 (1) and (4-H2dpye)[(4-dpye)(γ-Mo8O26)]0.5·2H2O (2) and [(3-H2dpyp)2(β-Mo8O26)]·2H2O (3) [(4-H2dpyp)2(β-Mo8O26)]·2H2O (4), have been hydrothermally prepared and structurally characterized by single crystal X-ray diffraction analyses. Compound 1 exhibits a 3D 6-connected supramolecular framework assembled from 1D γ-Mo8O26 inorganic chains and 3-H2dpye molecules. Compound 2 consists of an uncommon 1D γ-Mo8O26–4-dpye inorganic–organic hybrid chain connected by Mo–N bond, which are extended by 4-H2dpye molecules to a 3D 3,8-connected supramolecular framework. Compounds 3 and 4 show 3D 6,6-connected supramolecular framework and 2D 3,6-connected supramolecular layer based on β-Mo8O26 anions and 3/4-H2dpyp molecules via hydrogen bonds, respectively. The different bis-pyridyl-bis-amide ligands, isomers of octamolybdates and hydrogen bonding interactions in the title compounds show great effects on the final supramolecular networks. The electrochemical, electrocatalytic and photocatalytic activities of compounds 1–4 have been investigated.

A series of new polyoxometalate-based metal–organic complexes with different rigid pyridyl-bis(triazole) ligands: assembly, structures and electrochemical properties

Five new polyoxometalate (POM)-based metal–organic complexes (MOCs) with different rigid pyridyl-bis(triazole) ligands, namely, H{Co2(Hpyttz-I)2(H2O)6[CrMo6(OH)6O18]}·8H2O (1), {Co2(H2pyttz-I)2(H2O)4[TeMo6O24]}[Co(H2O)6]·3H2O (2), {Co3(Hpyttz-II)2(H2O)6[γ-Mo8O26]}·10H2O (3), {Ni3(Hpyttz-II)2(H2O)6[γ-Mo8O26]}·10H2O (4), {Ni3(Hpyttz-III)2(H2O)8[γ-Mo8O26]}·10H2O (5) (H2pyttz-I = 3-(pyrid-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, H2pyttz-II = 3-(pyrid-3-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, H2pyttz -III = 3-(pyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), were successfully synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Complex 1 is a two-dimensional (2D) supramolecular network based on the binuclear complex unit: [Co2(Hpyttz-I)2(H2O)6 [CrMo6(OH)6O18]]. Complex 2 is a 1D supramolecular chain derived from the binuclear cobalt complex: {Co2(H2pyttz-I)2(H2O)4[TeMo6O24]}2−, the discrete [Co(H2O)6]2+ units act as counter cations. Complexes 3 and 4 are isostructural with different center metals (M = Co or Ni), the adjacent γ-Mo8O264− anions are linked by the MII ions to form a 1D M-γ-Mo8O26 inorganic chain. Then 1D M-γ-Mo8O26 inorganic chains are linked together by the 1D metal–organic M-(Hpyttz-II) chains to form a 3D framework. In complex 5, γ-Mo8O264− anions are bridged by the NiII ions to give a 1D Ni-γ-Mo8O26 inorganic chain, the adjacent 1D Ni-γ-Mo8O26 chains are connected through [Ni(Hpyttz-III)2] units to form a 2D layer. The effect of POM type and coordination site of the ligands on the structures of the title complexes were discussed. The title complexes 1, 2 and 5 exhibit excellent bifunctional electrocatalytic activities toward the reduction of bromate/hydrogen peroxide and the oxidation of ascorbic acid. In addition, the redox potentials of complexes 1, 2 and 5 are highly sensitive to pH and may be used as a kind of potential pH sensor.

Novel polyoxometalate-based cobalt complexes based on rigid pyridyl-triazole-tetrazole and pyridyl-bis(triazole) ligands

Three novel polyoxometalate (POM)-based metal–organic complexes (MOCs) constructed from rigid pyridyl-triazole-tetrazole and pyridyl-bis(triazole) ligands have been hydrothermally synthesized and structurally characterized: [Co3(Htyptz)2(γ-Mo8O26)(H2O)6]·4H2O (1), H2[Co3(Htyptz)2(TeMo6O24)(H2O)8]·6H2O (2), [Co3(Hpyttz)2(γ-Mo8O26)(H2O)8]·2H2O (3) (H2typtz = 3-(tetrazol-5-yl)-5-(pyrid-3-yl)-1,2,4-triazolyl, H2pyttz = 3-(pyrid-4-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl). Single-crystal X-ray diffraction analyses reveal that complex 1 is a 3D metal–organic framework. Both 2 and 3 are 2D metal–organic architectures. In complex 1, the adjacent [γ-Mo8O26]4− anions are linked by the CoII ions to form a 1D Co-γ-Mo8O26 inorganic chain. Then the 1D Co-γ-Mo8O26 inorganic chains are linked together by the 1D metal–organic Co-Htyptz chains to form a 3D framework. In complex 2, the adjacent Co-Htyptz metal–organic chains are connected by TeMo6 polyoxoanions to form a 2D architecture. In complex 3, [γ-Mo8O26]4− anions are bridged by the CoII ions to give similar 1D Co-γ-Mo8O26 inorganic chains to those in 1, which are connected through [Co(Hpyttz)2] units to form a 2D network. 1 and 2 represent the first examples of POM-based MOCs derived from H2typtz. The effects of the POM type and different ligands on the structures of the title complexes were discussed. The adsorption activities for organic dyes methylene blue (MB), gentian violet (GV), methyl orange (MO), rhodamine B (RhB), neutral red (NR) and safranin T (ST) have been investigated in detail. Furthermore, the electrochemical properties of 1 and 2 have been studied, which display electrocatalytic activities toward the reduction of nitrite and bromate. 1-CPE shows pH-dependent electrochemical behaviors and may be used as a potential sensor.