The Study Of The Decoration Chemistry And Extend Structure Of Lacunary Heteropolytungstate

The transition metal-substituted polyoxotungstates have attracted great attention, which stems not only from their intriguing variety of architectures, but also from their potential applications in the fields as diverse as catalysis, medicine, molecular magnetism and materials science. In recent years, the decoration chemistry and extended-structure investigation based on lacunary heteropolytungstate have become an important research area of the polyoxometalate(POM) chemistry.In this paper, we have investigated the heteropolytungstate derivatives with pendant ligand through the decoration of the monovacant heteropolytungstate by 3d transition metal complexes; and we have obtained novel conjoined twin and sandwich structure through the decoration of the divacant heteropolytungstate by 3d transition metal; and we have obtained the extended structure of the Weakley (and Hervé) sandwich-type and monovacant Well-Dawson-type heteropolytungstate through the reaction of the 3d transition metal complexes and the trivacant heteropolytungstate or simple inorganic salts. The studies on synthetic conditions and rules, and the relationships between structures and properties for these compounds also are carried out.Twelve new decorated heteropolytungstates based on mono- and divacant heteropolytungstate building blocks have been synthesized via water solution synthesis methods, and four extended structures based on the trivacant heteropolytungstate subunits have been synthesized via hydrothermal reaction, and structurally characterized by elemental analyses, IR, TG, CV, XPS, ESR and single crystal X-ray diffractions. The stabilities and magnetic properties of these compounds have been studied.1. Three isomorphic pendant derivatives based on monovacant Keggin heteropolytungstate [SiW11O39]8- as building block have been synthesized through the decoration of Co-Im complexes using bench method: (Im)5Na₄H₂[SiW₁₁O₃₉CoIm]_0.63[SiW₁₁O₃₉Co(H₂O)]_0.37·7H₂O (1) (HIm)₆[SiW₁₁O₃₉NiIm]_0.8[SiW₁₁O₃₉Ni(H₂O)]_0.2·7H₂O (2) (Im)₄Na₆[SiW₁₁O₃₉MnIm]_0.69[SiW₁₁O₃₉Mn(H₂O)]_0.31·7.5H₂O (3) Complexes 1–3 are the first examples of crystallographically characterized 3d-transition metal mono-substituted POMs with an antenna organic ligand synthesized under normal bench conditions. An excess of organic ligand was used to inhibit the hydrolysis of the coordinated bond between transition metal and organic ligand. This strategy is an effective method for the synthesis of complexes 1–3. In this context, we have obtained a homologous pendant derivative in which the 4,4′-bpy was used instead of Im as pendant ligand: {Co(H2O)4(4,4′-bpy)}2(4,4′-Hbpy)2[SiW11Co(4,4′-bpy)O39]·5H2O (4) When using the monovacant Dawson-type heteropolytungstate [P2W17O61]10- as building block and Co-Im complexe as pendant ligand, another homologous pendant derivative have been obtained: (HIm)7H[P2W17O61Co(Im)]·4H2O (5) In the synthesis process of the compound 5, reducing amount of the Im ligand while other coditions were kept, a non-pendant derivative has been obtained: K6H2[P2W17O61Co(H2O)]·19H2O (6) In the Im and 4,4′-bpy grafting POM derivatives, both the Im and 4,4′-bpy as pendant ligands possess another"free"N atom that may act as a potentially coordinating site to other transition metal ions giving rise to more extended topology structures, or providing a biological activity.2. A series of conjoined twin and sandwiched derivatives based on divacant heteropolytungstateγ-SiW10 as building block have been synthesized through the decoration of transition metal Cu2+ ion using bench method: Na₈[Cu₄(H₂O)₂(OH)₄Si₂W₁₆O₅₈]·26H₂O (7) K₈[Cu₄(H₂O)₂(OH)₄Si₂W₁₆O₅₈]·28H₂O (8) Ca₄[Cu₄(H₂O)₂(OH)₄Si₂W₁₆O₅₈]·48H₂O (9) (HIm)₈[{K(H₂O)}₂{(μ3-H₂O)Mn(H₂O)}(Si₂W₂₀O₇₀)]·10H₂O (10) (HIm)₈[{K(H₂O)}₂{(μ3-H₂O)Co(H₂O)}(Si₂W₂₀O₇₀)]·9H₂O (11) (HIm)₈[{K(H₂O)}₂{(μ3-H₂O)Ni(H₂O)}(Si₂W₂₀O₇₀)]·9H₂O (12)The structures of compounds 7-9 are quite unique. In their structures the original lacunary POM skeletons are kept, and theγ-decatungstosilicates dimerize in an unprecedented side-by-side conjoined mode, resulting in the twin structure. The structure of this POM demonstrates for the first time the possibility of replacing W atoms with transition-metal atoms in the lacunary POM skeleton. Compounds 7-9 are ferromagnetically coupled Cu(II)-substituted dimers, and the ferromagnetic exchange interactions can be fitted primely.Compounds 10-12 are a kind of Wells–Dawson-like opened structure, in which a transition metal ion is sandwiched, exhibiting a character of both polymerization and sandwich structure. The structural stability in solution has been identified by the electrophoresis experiment. The outside water molecule located on the transition metal ion is expected to be further explored in catalysis domain.3. The high dimension framework base on the Weakley- and Hervé-type sandwich structures on the basis of trivacant heteropolytungstate subunits or simple inorganic salts have been synthesized using the transition metal complexes as bridged ligand under the hydrothermal conditions: H₂[Mn(en)₂]2[Mn(en)₂(H₂O)]2[Mn4(H₂O)₂(PW9O34)₂]·9H₂O (13) Na2[Co(en)₂]2[{Co(en)₂(H₂O)]2[Co4(H₂O)₂(PW9O34)₂]·9H₂O (14) (H₂en)₂[Mn(en)₂]6[Mn(en)₂(H₂O)]4[As2W19O67Mn2(H₂O)₂]2[VW12O40]·10H₂O (15)Compounds 13-14 exhibit 1D chain and 2D layer structures. They are first examples with high dimension frameworks in which the water molecules located on the Weakley sandwich belts are preserved.The component and structure of the compound 15 are very amusing in that both the sandwich- and keggin-type polyanions are coexistent in the crystal cell, and this is first example in POM chemistry. Three metal ions located on the sandwich belt have three kinds of coordination modes: the square-planar coordination, the square-pyramidal coordination, and the octahedron coordination. In the compound, the Hervé-type sandwich polyanions are firstly constructed to a high dimension framework by transition metal complexes. The 2D sandwich layer is unfamiliar in POM chemistry.4. According to the synthesis method of compound 15, a heteropolytungstate based on monovacant Wells-Dawson plyanion [α1-As2W17CuO61]8- as building block and Cu-en as bridged ligand has been synthesized: (Hen)2[Cu(en)2]{[Cu(en)2][Cu(en)2(H2O)]2(As2W17CuO61)]2}·10H2O (16) Compound 16 is a 1D chain strucure constructed from two double-bridged chains connected by Cu(en) groups.