Ming-Guan Liu

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.

Polyoxoanion-enveloped Ag/ptz inorganic–organic hybrid system: From a single to a double template

By changing the polyoxoanions in the same metal–organic system (Ag/ptz), two novel inorganic–organic hybrids: [Ag10(ptz)5(HP2W18O62)(H2O)4]·2H2O (1), [Ag7(ptz)5(H2SiW12O40)(H2O)] (2) (ptz = 5-(4-pyridyl)-tetrazolate), are synthesized under hydrothermal conditions, and characterized by IR spectra, elemental analyses and single crystal X-ray diffraction. Compound 1 and 2 show 3D POM-templated framework structures. In compound 1, a 2D layer is constructed by “shield-like” metal–organic circles templated by P2W18 polyoxoanions, which is extended to a 3D structure by covalent bonds in an interdigital mode. In compound 2, a 3D network is constructed by 2D layers and a “double bridge-pillar”, the Keggin polyoxoanion templates are enveloped in pairs in nanocages. The influences of polyoxoanion templates on the frameworks are discussed. The electrochemical behavior and luminescent properties for compound 1 and 2 are investigated.

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.