Hai-Jun Pang

The factors affecting on the assembly of Ag–H2biim system: size, charge or shape of polyanions?

By introducing different polyoxotungstates into the Ag–H2biim system, four new compounds with distinct architectures, Ag2(H2biim)4(W6O19)·2H2O (1), Ag6(H2biim)6(SiW12O40)(OH)2·2H2O (2), Ag6(H2biim)6(PW12O40)(OH)3·H2O (3) and Ag6(H2biim)6(P2W18O62)·12H2O (4) (H2biim = 2,2′-biimidazole), have been hydrothermally synthesized, and characterized by routine physical methods and single crystal X-ray diffraction. In compound 1, the Lindqvist type polyoxotungstate {W6} combines with the chelate Ag–H2biim complex forming a discrete “dumbbell-like” motif. Isostructural compounds 2 and 3 are obtained by introducing Keggin polyoxotungstates ({SiW12} and {PW12}, respectively), which show a 2D layer structure. The 2D layers parallel each other to form a 3D supramolecular framework. The larger Wells–Dawson polyoxotungstate {P2W18} directs the formation of compound 4, in which one 2D layer is the inversion of the neighboring ones. Furthermore, there exist infinite Ag chains in compounds 2–4, which are quite unusual in POM-based compounds. The distinction among the final four architectures is ascribed to the structure-directing effect of different polyanions. The electrochemical properties of compounds 1–4 are studied. In addition, the antibacterial properties of the four compounds against negative Escherichia coli (E. coli) and positive Staphylococcus aureus are investigated.

Assembly of two new polyoxometalate-templated supramolecular compounds by utilizing a ligand with a combination of rigidness and flexibility

Two new polyoxometalate-templated compounds, (bix)[Cu(bix)]3[PW12O40]·4H2O (1), and [Cu(bix)]3[PMo12O40] (2) (bix = 1,4-bis(imidazol-1-ylmethyl)benzene), were hydrothermally synthesized, and characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, and single X-ray diffraction. In compound 1, the Keggin polyanions [PW12O40]3− direct the [Cu(bix)] coordination polymeric chains to form a 3D supramolecular framework with grid-like 2D channels. By changing the polyanions into [PMo12O40]3−, compound 2 is obtained, in which the [Cu(bix)] coordination polymeric chains array around the polyanions to construct a 3D supramolecular framework with 1D hexagon-like channels. Their different structures show the template effect of the polyanions. Additionally, the cyclic voltammetry measurements indicate that the supramolecular compounds keep the redox properties of their parent polyanions.

Preparation and application of multiple-component-doped keggin polyoxometalate microtubes--towards a component-tunable hollow structure.

In this paper, the preparation of ascorbic acid (AA)-doped polyoxometalate (SiW(12)-AA) microtubes is described. The SiW(12)-AA microtubes convert to heteropoly blue microtubes upon exposure to ammonia gas, which is an ammonia-triggered solid-solid redox reaction between AA molecules and polyoxometalates, and can possibly be applied to a chemical sensor for detecting ammonia and volatile organic amines. Furthermore, the SiW(12)-AA microtubes have been applied to the in situ synthesis of Ag nanoparticles (NPs) through the redox reaction between the AA component and Ag(+) ions occurring on the surfaces of the SiW(12)-AA microtubes to give silver NPs immobilized on polyoxometalate microtubes (Ag@SiW(12)).

Two inorganic chains based on the Anderson-type polyanions and transition metals

Two new compounds based on Anderson-type polyanions, H(C6H9N3O2)2[Mn(H2O)2][Al(OH)6Mo6O18] ⋅ 6H2O (1) and (C6H10N3O2)2[Ag(H2O)2][Cr(OH)6Mo6O18] ⋅ 6H2O (2), have been synthesized in aqueous solution and characterized by elemental analyses, IR, TG, and single crystal X-ray diffraction. Both compounds show inorganic 1-D chain-like structures in which the Anderson-type polyanions are bidentate ligands chelating to two metal cations. Further, transition metal cations are in the same line with the center Al (Cr), which is unusual in 1-D inorganic chains based on Anderson-type polyanions. Free histidine molecules further link the chains into 3-D supramolecular frameworks via hydrogen interactions. Electrochemical and fluorescence quenching properties were investigated.

A water chain with trimeric/hexameric clusters trapped in a POM/Ln compound

A new 3-D supramolecular compound based on a Keggin polyoxometalate and lanthanide (Ln) coordination cations [Ce(H2O)3L3]2[HSiMo12O40]2[L] ⋅ 7H2O (1) (L = isonicotinic acid) has been synthesized and characterized by routine methods. Compound 1 has a water chain with trimeric and hexameric water clusters trapped in the network. The isonicotinic acid plays a key role in forming the 1-D water chains. Compound 1 shows intense photoluminescence at room temperature.

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.

Synthesis and Characterization of a Three-dimensional Porous Compound: [Cu(H2O)6][{Cu(H2O)2}2{Cu(H2O)4H4W12O42}] · 12H2O

A novel transition metal polyoxotungstate, [Cu(H2O)6][{Cu(H2O)2}2{Cu(H2O)4H4W12O42}] · 12H2O (1), has been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV/vis spectroscopy, and TG analysis. The paradodecatungstate anions [H2W12O42]10− are linked by CuO6 octahedra, forming a three-dimensional (3D) structure. The magnetic susceptibility of compound 1 in the temperature range 2 - 300 K shows the presence of antiferromagnetic interactions within the uniform Cu2・ ・ ・Cu3 chains

Two α-metatungstate compounds containing supramolecular helical chains

[Co(bipy)3]3[{Co(bipy)2(H2O)}2{H3W12O40}2] · H2O (1) and [H2bipy]0.5[{Cu(bipy)2}2{H3W12O40}] · H2O (2) (bipy = 2,2′-pyridine) have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, and TG analyses. In 1, there exist supramolecular left/right-helical chains constructed by [Co1(bipy)3]2+ and these chains perpendicularly interact with a series of parallel POM double-chains composed of [{Co(bipy)2(H2O)}2{H3W12O40}2]6− anions and [Co2(bipy)3]2+ cations forming a 3-D supramolecular network. In 2, there also exist supramolecular left-/right-helical chains constructed by [{Cu(bipy)2}2{H3W12O40}]− fragments. Furthermore, these left-/right-helical chains are linked together via H-bonds forming interesting enantiomorphous chiral layers. Electrochemical properties of these compounds have been studied.

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.