| On the basis of molecular design, six tetra- and hexa-nuclear sandwich-type composites based on trivacant Keggin heteropolyanions, and three complexes based on novel polyoxometalate building units were successfully synthesized from heteropolyanion precursor and raw materials under hydrothermal conditions, which were characterized by X-ray crystallography, spectroscopic, thermal, and magnetic properties.(1) We have synthesized two tetranuclear Fe(Ⅲ)-substituted tungstoironates: [dapH2]3[enH2]2[NaFe4(H2O)2(FeW9O34)2]·7H2O (1) and [dapH2]5[Fe4(H2O)2 (FeW9O34)2]·11H2O (2). They represent the first examples of iron-containing tungstoironates and 1 further forms a two-dimensional framework through special connectivity.(2) We obtained two sandwich-type compounds based on [B-SbW9O33]9- building units: [Co4.5W1.5(H2O)10(β-SbW9O33)2]·2.5H2O (3),Na(enH2)4H2[Na(Cu(H2O))3 (α-SbW9O33)2]·8H2O (4). Compound 3 displays an offset hexanuclear sandwich-type polyanion framework, but compound 4 presents a symmetrical tetranuclear sandwich-type dimeric compound.(3) Using raw materials, we have synthesized two tetranuclear Co(Ⅱ)-substituted tungstogermanates: [enH2][C8N4H22]3H2[Co4(enH)2(GeW9O34)2]·6H2O (5), [Co (en)3]2H6[Co4(enH)2(GeW9O34)2]·14H2O (6), both of which are isolated structures with offset sandwich-type polyanions [GeW9O34]10-.(4) Under hydrothermal synthetic technology using [B-SbW9O33]9- precursor, we have obtained an organic-inorganic composite, [enH2]3H3[SbW18O60]·7H2O(7) (7). The result of the single crystal X-ray diffraction analysis shows the compound presents a novel Dawson-like structure.(5) Using simple oxides, we have synthesized a new vanadium antumonate complex [{Ni(en)2}2Sb8V14O42·5.5H2O (8), which presents a beautiful two-dimensional network.(6) Under special hydrothermal condition, we have synthesized the first example of two-dimensional organic-inorganic composite ferric molybdate [enH2][Fe2(MoO4)4] (9), which displays unique connectivity fashion.
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