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The heptamolybdate [NH4]6[Mo7O24], as a common polyoxometalate (POM) precursor with dynamic configuration transformation in aqueous solution by changing the pH, has been introduced into the hydrothermal reaction system containing copper ions and bichelate-bridging ligands, leading to the isolation of seven new organic-inorganic hybrid compounds [CuI 2Lo2][Mo6O19] (1), [CuII 2Lo2][β- Mo8O26]⋅2H2O (2), [CuII 4Lo2(pypz)4][α-Mo8O26]⋅3H2O (3), [CuII 4Lp4(H2O)4][α-Mo8O26][β-Mo8O26]⋅4H2O (4), [CuI 4Lp3][β-Mo8O26]⋅H2O (5), pCuI 4Lp4][α-Mo8O26] (6), and [CuI 2Lp2(Emim)2]ijβ-Mo8O26] (7) [bis(3-(2-pyridyl)pyrazole-1-ylmethyl)benzene = bppmb, Lo = 1,2-bppmb, Lp = 1,4-bppmb, pypz = 3- (2-pyridyl)pyrazole, Emim = 1-ethyl-3-methylimidazolium). All compounds were characterized by elemental analysis, IR spectroscopy, TG analysis, powder X-ray diffraction and single-crystal X-ray diffraction analysis. The structural analyses show that the isopolymolybdate clusters act as a type of "molecular adaptor", which modulate the coordination mode of metal-organic subunits, leading to a series of new metal-organic secondary building units, such as the "Möbius-Ring"-type binuclear unit, "S"-type binuclear unit, butterfly-type unit, helical chain and mesomeric helical chain. As a result, the POM anions and the metal-organic subunits have suitable matching modes to form new hybrid self-assemblies. The photocatalytic properties of compounds 1-7 for the degradation of Rhodamine-B (RhB) under UV irradiation were investigated. All compounds showed good catalytic activity. Furthermore, the luminescent properties of compounds 1-7 have also been explored, indicating an organic ligand-based emission mode for all compounds. [ABSTRACT FROM AUTHOR]

With the bottom-up design principle, we use metal-ions to bridge the predesigned tectons (1[(H2L1)2(Mo8O26)]·4H2O and 3[(H2L2)(L2)0.5(Mo8O26)0.5]·H2O) so that two higher dimensional γ-octamolybdate based inorganic–organic hybrid compounds 2[CuI2(L1)3(Mo8O26)0.5] and 4[Ni(L2)2(HL2)2(Mo8O26)]·4H2O are successfully obtained. [ABSTRACT FROM AUTHOR]

Here, we report two novel POM-based MOFs: a nano-caged hybrid compound [Ni2(BIMB)2(MoVI4MoV2O19)] (1), whose cages are based on [Mo6O19]4−units and a [Mo6O19]2−-templated framework [Zn4(BIMB)4(PO4)2(Mo6O19)]·2H2O (2) (BIMB = 1,4-bis(1-imidazolyl)benzene). According to topological analysis, the first is a 3D (4,6)-connected self-penetrating framework with polycatenanes motif. In contrast, the second metal–organic framework has no interpenetration for the templated [Mo6O19]2−occupying the cavity. The UV-vis absorption spectrum of 1was investigated to prove the existence of MoVatoms and the typical peak at 577 nm can be attributed to MoV→ MoVIcharge transfer. Furthermore, the diffuse reflectivity spectrum shows that its band gap can be assessed as 3.06 eV, which can be regarded as a wide gap semiconductor. Additionally, cyclic voltammogram of compound 1shows two redox peaks in the range of 0–800 mV in H2SO4aqueous solution. [ABSTRACT FROM AUTHOR]

Six new transition-metal complexes modified octamolybdate compounds have been successfully synthesized with two kinds of V-shaped flexible organic ligands under hydrothermal conditions, namely, [CuII(HL1)2(H2O)2(Mo8O26)] (1), [CuII(L1)2(Mo8O26)0.5] (2), [CuII(HL2)2(Mo8O26)]·2H2O (3), [CuII2(L2)4(Mo8O26)]·3H2O (4), [CuI3(L2)2(Mo8O26)0.5Cl] (5), [CuI4(L2)4(Mo8O26)] (6) where L1= 3-((1H-imidazol-1-yl)methyl)pyridine, L2= 3-((1H-1,2,4-triazol-1-yl)methyl)pyridine. Their crystal structures have been determined by X-ray single-crystal diffraction, elemental analyses, IR spectra, and thermogravimetric analyses (TGA). With L1ligand, two compounds were obtained: compound 1is a 1D β-octamolybdate based chain and compound 2is a 2D 4-connected network most strikingly, whose octamolybdate anion shows a -isomer. With L2ligand, compounds 3, 4, 5and 6were obtained, respectively. In compound 3, 1D β-octamolybdate-based metal–organic chains are further extended by hydrogen bonds to build a 3D supramolecular structure, while in compound 4, every two adjacent double-helical metal–organic chains are bridged by β-octamolybdate anions to generate a 2D 3-connected network. When CuSO4·5H2O was substituted by CuCl, two CuIcompounds were attained. Interestingly, in compound 5the octamolybdate anion threads through the metal–organic loop presenting a fascinating 2D polythreading topology, and in compound 6the octamolybdate anions pillar the railroad-like metal–organic strands to generate a 2D 3-connected network. The structural differences among compounds 1–6indicate the importance of the different coordination mode of organic ligands and various polyoxoanions, and of the pH values of the systems for the framework formation. Furthermore, the semiconducting properties of compounds 1–5were investigated, and photoluminescence as well as photoconductivity for compound 5were also studied. Compound 5has a comparatively lower band gap and is photoconductive in the UV-vis range, so it can be potentially applied as a semiconductor of photoelectronic detectors. [ABSTRACT FROM AUTHOR]

Two novel nanoporous metal–organic frameworks (MOFs) based on the same binuclear nickel secondary building units, {[Ni2(H2O)(BDC)2(BIMB)2]·6DMF}n(1) and {[Ni2(H2O)(BDC)2(BIMB)2]·5DMAc}n(2) (H2BDC = terephthalic acid, BIMB = 1,4-bis(1-imidazolyl)benzene and DMF = N,N′-dimethylformamide, DMAc = N,N′-dimethylacetamide) have been synthesized by self-assembly of Ni(NO3)2·6H2O, BIMB and H2BDC in different solvents (DMF and DMAc), respectively. Different linking modes between terephthalate and binuclear nickel building units in 1and 2lead to an interesting phenomenon that their host frameworks are isomeric to each other and have the same three periodic eight-connected self-penetrating nets with novel 420.68topology. Powder X-ray diffraction (PXRD) results indicate that 1and 2both have reversible framework transformations in an acetone/guest solvent molecule system. [ABSTRACT FROM AUTHOR]

Two Fe-substituted Dawson-type nanoscale selenotungstate clusters, {Fe6Se6W34} and {Fe10Se8W62} involving {α-Se2W14} and {γ-Se2W14} building blocks, have been isolated, which exhibit photocatalytic H2 evolution activity. Their electrochemical behaviours and magnetic properties were also investigated. [ABSTRACT FROM AUTHOR]