Zhihan Chang

Two novel octamolybdate-based frameworks decorated by flexible bis-pyridyl-bis-amide ligands with different spacer lengths

Two octamolybdate hybrid complexes based on flexible bis-pyridyl-bis-amide ligands with different spacer lengths, namely, {[Cu(L1)(β-Mo8O26)0.5(H2O)2]·H2O}n (1), [Cu(L2)(β-Mo8O26)0.5(H2O)] (2) (L1 = N,N′-bis(3-pyridinecarboxamide)-1,2-ethane, L2 = N,N′-bis(3-pyridinecarboxamide)-1,6-hexane), have been successfully synthesized. Crystal structure analysis reveals that 1 is a two-dimensional (2D) network constructed from [Cu-L1]n2n+ chains and [β-Mo8O26]n4n− anions, displaying a 4-connected framework with 32·62·72 topology. Compound 2 consists of double one-dimensional (1D) meso-helical chains and 1D inorganic chains to generate a three-dimensional (3D) framework with a (4,4)-connected (4·64·8)2(42·62·82) topology. The title compounds represent the first examples of introducing a flexible bis-pyridyl-bis-amide ligand into the isopolymolybdates system. In addition, the electrochemical behavior of 1, luminescent properties and photocatalytic activities of the title compounds have been investigated.

Two novel Anderson-type polyoxometalate-based metal–organic complexes with high-efficiency photocatalysis towards degradation of organic dyes under UV and visible light irradiation

Two novel Anderson-type polyoxometalate (POM)-based metal–organic complexes (MOCs), namely, H{CuL0.51 [CrMo6(OH)6O18](H2O)}·0.5L1 (1) and {Cu2(L2)2[CrMo6(OH)5O19](H2O)2}·2H2O (2) (L1 = N,N′-bis(3-pyridinecarboxamide)-1,2-ethane, L2 = N,N′-bis(3-pyridinecarboxamide)-1.3-propane), 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 bidentate [CrMo6(OH)6O18]3− (CrMo6) polyoxoanions bridge the CuII ions to generate a 1D Cu–CrMo6 inorganic chain, which is further connected by the μ2-bridging L1 ligands to form a 1D ladder-like chain. Complex 2 is a 3D POM-based metal–organic framework exhibiting a {412.63} topology, which is constructed from the quadridentate CrMo6 polyoxoanions and μ2-bridging L2 ligands. The flexible bis-pyridyl-bis-amide ligands with different spacer lengths have a significant effect on the final structures. In addition, pH shows great influence on the formation of the single-crystal phase. The photocatalytic activities of the title complexes on the degradation of methylene blue (MB) and rhodamine B (RhB) under UV and visible light have been investigated in detail.

Effect of polyoxoanions and amide group coordination modes on the assembly of polyoxometalate-based metal–organic complexes constructed from a semi-rigid bis-pyridyl-bis-amide ligand

A series of polyoxometalate (POM)-based metal–organic complexes constructed from a semi-rigid bis-pyridyl-bis-amide ligand have been hydrothermally synthesized and structurally characterized: [Cu2L2(PMoVI11MoVO40)(H2O)2]·2H2O (1), [Cu2L2(PWVI11WVO40)(H2O)6]·H2O (2), [Cu2L2(SiW12O40)(H2O)6]·H2O (3) and [Cu2L2(H2K2Mo8O28)(H2O)2] (4) (L = N,N′-bis(3-pyridinecarboxamide)-piperazine). Single-crystal X-ray analyses reveal that complex 1 is a 2D metal–organic architecture based on the Keggin-type [PMoVI11MoVO40]4− anions and quadrate Cu2L2 loops. Isostructural complexes 2 and 3 display 2D supramolecular networks based on 1D infinite chains, which are constructed from quadrate Cu2L2 loops and Keggin polyoxoanions. Complex 4 exhibits a 3D metal–organic framework derived from the newly-reported [K2Mo8O28]6− polyoxoanions and quadrate Cu2L2 loops. The L ligands show a μ3-bridging coordination mode (via ligation of two pyridyl nitrogen atoms and one carbonyl oxygen atom) in 1 and 4, and a μ2-bridging coordination mode (via ligation of two pyridyl nitrogen atoms) in 2 and 3, forming Cu2L2 loops in 1–4. The influence of amide group coordination modes and structural features of POMs on the structures of the title complexes has been discussed. The electrochemical properties and selective photocatalytic properties of the title complexes have been reported in this article.

A novel polyoxometalate templated microporous metal–organic framework with electrochemical properties

A novel Wells–Dawson polyoxometalate-templated 3D microporous metal–organic framework (MOF), namely, H6[Cu3(H2O)6(P2W18O62)2(3-dpye)6]·28H2O (1) (3-dpye = N,N′-bis(3-pyridinecarboxamide)-1,2-ethane), was hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Each Cu(II) ion acts as a four-connected node linking four 3-dpye ligands to construct a 3D microporous host MOF containing left-handed helical chains, in which the P2W18O626− anions reside. 1 represents the first example of 3D MOFs with an 86 uniform net containing non-coordinating Wells–Dawson anions. The electrochemical properties have been investigated in detail.

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.

Assembly, structures, photophysical properties and photocatalytic activities of a series of coordination polymers constructed from semi-rigid bis-pyridyl-bis-amide and benzenetricarboxylic acid

A series of new metal(II)–organic coordination polymers, namely [Co(3-DPNA)(1,3,5-HBTC)]·2H2O (1), [Ni(3-DPNA)1.5(1,3,5-HBTC)(H2O)2] (2), [Cu(3-DPNA)(1,3,5-HBTC)]·H2O (3), [Zn(3-DPNA)(1,3,5-HBTC)]·2H2O (4), [Cd(3-DPNA)(1,3,5-HBTC)(H2O)]·2H2O (5), [Co(4-DPNA)(1,3,5-HBTC)]·4H2O (6), [Ni(4-DPNA)(1,3,5-BTC)2/3] (7), [Cu(4-DPNA)(1,3,5-BTC)2/3] (8), [Zn(4-HDPNA)(1,3,5-BTC)] (9), [Cd(4-DPNA)(1,3,5-BTC)1/3Cl] (10), have been purposefully synthesized under hydrothermal conditions [N1,N4-di(pyridin-3-yl)naphthalene-1,4-dicarboxamide (3-DPNA) and N1,N4-di(pyridin-4-yl)naphthalene-1,4-dicarboxamide (4-DPNA), 1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid]. Complexes 1 and 4 exhibit similar 1D belt-like chains constructed from 1D left- and right-hand [Co-(3-DPNA)]n helical chains and [Co-(1,3,5-HBTC)]n linear chains. Complex 2 furnishes a 1D [Ni-(3-DPNA)1.5]n “loop + line” chain with 1,3,5-HBTC anions hanging on both sides. Complex 3 features a 2D sql network based on [Cu-(3-DPNA)]nmeso-helical chains and [Cu-(1,3,5-HBTC)]n linear chains. Complex 5 shows a 1D ladder-like chain constructed from [Cd-1,3,5-HBTC]n linear chains and [Cd2(3-DPNA)2] loops. Complex 6 displays a 2D double sheet containing (H2O)8 clusters. Complexes 7 and 8 possess similar 3D (3,4)-connected frameworks with the (63)2(64·8·10)3 topology containing a dodecagon-shape cavity and a hexagonal cavity, respectively. Complex 9 shows a 2D network, in which one pyridine nitrogen atom of 4-DPNA was protonated. Complex 10 is a 3D (3,5)-connected framework with (3·44·63·82)3(63) topology. All the 1D chains and 2D networks are further extended into 2D supramolecular sheets or 3D supramolecular frameworks through hydrogen-bonding interactions. The influence of metal(II) ions and N-donor ligands on the structures of the title compounds was investigated. The results suggest that the central metals with various coordination nature and the semi-rigid bis-pyridyl-bis-amide ligands with different coordination sites show a great effect on the structures of the title compounds. In addition, the fluorescence sensing properties of 4, 5, 9, and 10 and the photocatalytic activities of complexes 1–10 have been investigated in detail, and the results show that 5 possesses good fluorescence selectivity for different solvent molecules.

Application of flexible bis-pyrazine–bis-amide ligands to construct various polyoxometalate-based metal–organic complexes

By introducing the flexible bis-pyrazine–bis-amide ligands into a polyoxometalates (POMs) system, five POM-based metal–organic complexes, {Cu3(L1)2[CrMo6(OH)6O18]2(H2O)2}·10H2O (1), [CuL1(Mo8O26)0.5]·H2O (2), [Cu2(L1)2(HPMoVI10MoV2O40) (H2O)2]·2H2O (3), [Cu2(L1)2(SiMo12O40) (H2O)2]·2H2O (4), [Cu2(L2)2(SiMo12O40)]·2H2O (5) [L1 = N,N′-bis(2-pyrazinecarboxamide)-1,3-propane, L2 = N,N′-bis(2-pyrizinecarboxamide)-1,6-hexane], were synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and thermal gravimetric analyses (TG). Single-crystal X-ray analysis reveals that compound 1 is a 1D infinite ribbon-like chain with Anderson type polyanions [CrMo6(OH)6O18]3− as building blocks. Compound 2 is a 2D layer constructed from 1D helical [Cu-L1]n2n+ chains and [Mo8O26]4− anions, in which the octamolybdates also act as inorganic building blocks. Compounds 3 and 4 are isostructural, and display 2D supramolecular networks based on the 1D [Cu-L1]n2n+ chains, in which the Keggin polyanions serve as noncoordinated templates. Compound 5 is a 3D supramolecular framework constructed from the 2D [Cu-L2]n2n+ layers and the Keggin [SiMo12O40]4− polyanion templates. In compounds 1–4, the L1 ligands display the same symmetric coordination mode with two chelating sites. When lengthening the spacer of the ligand, L2 exhibits an asymmetric coordination mode in compound 5. The structural diversities of 1–5 show that the different polyoxoanions and spacer lengths of the ligands play key roles in the construction of various architectures. The title compounds represent the first examples of introducing flexible bis-pyrazine–bis-amide ligands into the POMs system. In addition, the electrochemical properties of compounds 2–5 and the photocatalytic activities of the title compounds on the degradation of methylene blue (MB) under UV, visible light and sunlight irradiation have been investigated in detail.

A twofold interpenetrating 3D Keggin-based Ag(I) complex based on a flexible bis-pyridyl-bis-amide

A Keggin-type polyoxometalate (POM)-based complex, [Ag5(L)3 (H2O)2]·6H2O (1) (L = N,N′-bis(3-pyridinecarboxamide)-1,2-ethane), has been hydrothermally synthesized. Compound 1 shows a 3D + 3D interpenetrating network with a (3,4,4,4)-connected (4 × 62)2(42 × 62 × 82)(65 × 8)2 topology, and it represents the first example of interpenetrating POM-based complex based on flexible bis-pyridyl-bis-amide ligands. Moreover, the electrochemical behavior and luminescence of 1 have been investigated.

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.