| Polyoxometalates (POMs), a well-known class of metal oxygen clusters with a large variety of compositions and structures, have been extensively studied because of their potential application in areas of catalysis, materials science, medicine, etc. By using polyoxometalate anions as building blocks, a variety of covalent assembly and incorporation to form one-dimension (1D) chain, 2D layer and 3D network architectures has produced many new solid state materials with functional properties. In particular, the incorporation of lanthanides (Ln) into POM can form a new class of materials with useful optical, magnetic and luminescent properties. Thus, the syntheses of lathanopolyoxometaltes (LnPOMs) have recently attracted considerable attention. Continuing interest in this field largely focuses on rational syntheses of complexes with extended polymeric structure. Here, we successfully synthesize the sandwich type polyoxometalate containing Ln (Ln=CeIV, PrIII) with the composition of (NH4)2[N(CH3)4]6Na2[Ce(PW11O392]·14H2O(1) and [(CH3)4NH]4Na3[Pr(PW11O39)2]·12H2O(2), which are 1D zigzag chain constructed from sandwich-type LnPOMs and the sodium cations. Both complexes were characterized by IR and single crystal X-ray diffractions. X-ray diffraction result reveals that the sandwich-type polyanions are linked by sodium ions to form a structure of zigzag chains, and the chains are further connected into an extensive two-dimensional (2D) framework depending on hydrogen bond.Cyclic voltammetry of these compounds, magnetic properties and fluorescent activity of 2 have been studied. Magnetic susceptibility measurement for 2 in the temperature range 2-300K reveal the occurrence of antiferromagnetic interactions between neighbor Pr (III) ions. The emission spectrum result shows weak photoluminescence of compound 2. The POM-containing composite films were prepared by the method of sol-gel via spin-coating and calcinations techniques. The structure integrity of the starting POMs in the as-synthesized composite films was confirmed by FT-IR. It was shown from the results that the strong chemical interaction between POM molecules and Tatiana networks existed on the films. The photocatalytic activities of the POM/TiO2 composite films were tested via degradation of formaldehyde gas. It was observed that the photocatalytic activities of the POM/TiO2 composite films are higher than that of the pure TiO2film.this mainly attributed to the synergetic effect between POM and TiO2.Further we utilize other building blocks as precursors for synthesis of novel solid-state compounds with first-row transition metals, lanthanides, etc. |
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