Fan-Xia Meng

Two organic–inorganic hybrids based on polyoxometalates: synthesis, crystal structure, and characterization

Two new Keggin- and Wells-Dawson-type polyoxometalate-based organic–inorganic hybrid copper–organonitrogen complexes have been synthesized under hydrothermal conditions: [CuI(4,4′-bpy)]2[H2SiW12O40] ⋅ 2H2O (4,4′-bpy = 4,4′-bipyridine) (1) and (en =ethylenediamine), and characterized by elemental analysis, IR spectra, TGA, XRD, and single crystal X-ray diffraction. In 1, [Cu(4,4′-bpy)]+ cations form polymeric chains and a weak Cu–O linkage makes the anions situate between two chains, forming an infinite 1-D ladder-chain structure. Such 1-D ladder-chains are further interconnected via hydrogen bonding into a 3-D supramolecular framework. Compound 2 with covalently bonded 3-D structure consists of saturated Wells-Dawson tungstoarsenate polyoxoanions and copper complexes with two types (rigid and flexible) of ligands. The polyoxoanion has the highest connectivity for Wells-Dawson tungstoarsenate polyoxoanion coordination polymers to date. XPS spectra indicate that three W atoms in the Dawson unit were reduced and that there coexist CuI and CuII in 2.

Syntheses, structures and properties of three neutral bisupporting heteropolyoxometalates

Three neutral polyoxometalates [PVW11O40{M(phen)2H2O}2] · 3H2O (phen = 1,10′-phenanthroline, M=Co 1, Zn 2, Ni 3) are composed of water and the neutral Keggin-type polyoxometallate covalently linking a pair of transition metal complex fragments on opposite sides. The transition metal lies in the center of a distorted octahedron. Multi hydrogen-bonding interactions between coordinated waters of neutral polyoxometalate molecules and terminal oxygen atoms of Keggin units and between bridging oxygens of Keggin units and lattice water create a two dimensional layer and between the layers there exist van der Waals forces. The framework of the neutral molecule begins to decompose at ca 500°C. Compound 1 exhibits a weak antiferromagnetic interaction in the 2–300 K range.

Metal–oxo cluster-supported transition metal complexes: hydrothermal synthesis and characterization of [{Cu(phen)2}2SiW12O40]

A new neutral α-Keggin polyoxometalate, [{Cu(phen)2}2SiW12O40] (1) (phen = 1,10-phenanthroline) was hydrothermally synthesized and characterized by IR, TG and single-crystal X-ray diffraction. The compound is monoclinic, space group P21/c with a = 26.065(5), b = 11.867(2), c = 23.385(5) Å, β = 113.78(3)°, V = 6619 Å3, Z = 4. X-ray analysis showed that both [Cu(phen)2]2+ units are supported on the α-Keggin polyoxoanion [SiW12O40]4− via the surface bridging and terminal oxygen atoms of two non-adjacent WO6 octahedra; these show unusual coordination environments. One Cu ion displays distorted trigonal bipyramidal geometry and the other square pyramidal. The unusual coexistence of complexes with different geometries is most likely caused by steric effects involving surface oxygen atoms of the heteropolytungstate and phen, which prevent the presence of a sixth coordinating atom. Weak π–π stacking interactions between phen groups give a 1D chain-like structure and hydrogen bonds are responsible for extended 2D and 3D motifs in the crystal.

An inorganic-organic compound with 1D honeycomb-like channels constructed from non-covalent linkage: synthesis and properties

An inorganic-organic hybrid compound {[Cu(phen)3]2PW11VO40  · 2H2O (1) has been hydrothermally prepared and structurally characterized by elemental analyses, IR, CV, TG, magnetic susceptibility measurements and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic space group C2/c with a  = 27.232(2) Å, b  = 25.351(2) Å, c  = 16.2748 (4) Å,  β = 105.20°, V  = 10842.3 Å3, Z  = 4, R1  = 0.0490 and wR2  = 0.1362. The structure of 1 exhibits a three-dimensional supramolecular network, formed by hydrogen-bonding and π–π stacking interactions. The three-dimensional network consists of one-dimensional honeycomb channels, which accommodate free water molecules. The size of the channel is 10.4  × 10.4 Å. Electrochemistry of 1 shows it undergoes three one-electron reversible redox processes. Variable-temperature magnetic measurements show typical antiferromagnetic interactions in the 2–300 K temperature range.

Anionic Structure‐Controlled Architecture with Copper Coordination Cations and Polyoxoanions and Application to Photocatalytic Decolorization of Dye Waste water

Synthesis and crystal structure of an ionic compound consisting of decatungstate anion W10O32 4‐ and cupper coordination cations in the form of a cationic stacking column are reported. The effect of anions on the stacking pattern of the coordinating cations and crystal structure is discussed in combination with other compounds. Application of the compound to the photocatalytic decolorization of dye wastewater has also been tested and reported here.

Synthesis, Crystal Structure and Thermal Stability of Homopolytungstate Supporting Nickel（II） Coordination Fragments

The organo-inorganic hybrid compound [Ni(phen)3] [(H2W12O40) {Ni(phen)2H2O} {Ni(trien)}] · 2H2O was synthesized from Na2WO4, · 2H2O, NiSO4 · 6H2O, CH3COOK, triethylenetetramine and 1,10-phenanthroline in water by the hydrothermal reaction, and characterized by IR, X-ray single crystal diffraction, and TG-DTA analysis. This compound crystallized in the monoclinic system, space group P2 (1)/n, with lattice constants: a = 1. 80998(6) nm, b = 2. 36504(8) nm, c = 2. 29199(7) nm, β = 110. 2220(10)·, V = 9. 2065(5) nm, Z = 4. Final R indices R1 = 0. 0532, wR2 = 0. 1295. The compound is decomposed at 593 °C.

Two Novel One-dimensional Inorganic-Organic Hybrids Constructed from [H2W12O40]6– Clusters and Lanthanide-organic Complexes: [(C5H5N-CO2)2Ln(H2O)3]2[H2W12O40]·nH2O (C5H5N-CO2 = Pyridine-4-carboxylate; Ln = La3+, n = 5; Ce3+, n = 7)

Two novel polyoxotungstate-based rare earth compounds, [(C5H5N-CO2)2Ln(H2O)3]2- [H2W12O40] · nH2O (C5H5N-CO2 = pyridine-4-carboxylate; Ln = La3+ (1), n = 5; Ce3+ (2), n = 7), have been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra and TG analyses. The isostructural compounds 1 and 2 exhibit onedimensional (1D) zig-zag chains, in which the dinuclear lanthanide complexes act as bridging linkers and the [H2W12O40]6− groups serve as bidentate ligands. The results of cyclic voltammetry (CV) show that compounds 1 and 2 undergo two two-electron redox processes, similar to that of the parent (NH4)6[H2W12O40] ·3H2O, and also reveal that the pH of the supporting electrolytic solution has a notable effect on the electrochemical behavior of compound 2.

Synthesis, Crystal Structure, and Spectral Characterization of Novel Three-dimensional Supramolecular Networks with One-dimensional Channels Based on Keggin-type Polyoxoanions and Mixed-Valence Dibenzotetrathiafulvalenes

A new organic/inorganic salt formed by mixed-valence dibenzotetrathiafulvalene (DBTTF) radical cations and the spherical Keggin-type polyoxometalate anions [H3BW12O40]2− was obtained by electrochemical oxidation of the donor in an acetonitrile and a 1,2-dichloroethane solution containing the polyanion. The compound has been characterized by X-ray diffraction, elemental analysis, EPR, IR and Raman spectroscopy. X-Ray diffraction experiments have revealed that the compound consists of heteropolyanions, water molecules and DBTTF radical cations. The organic radicals form trimers and dimers via π-π stacking; moreover, the polyoxoanions and the organic donors are also held together by hydrogen bonding interactions. In their packing arrangement, a three-dimensional supramolecular network with one-dimensional channels along the b axis is established with uncoordinated water molecules residing in the channels.