Effect of ring coordination of pyridine-3,5-dicarboxylate and metatungstate to Ln ions on metatungstate structure: Synthesis, structure and optical property of four new compounds

Four novel compounds based on α-metatungstate [H2W12O40]6− (W12) and Ln–organic complexes, (NH4)4[Ln2(L)2(H2O)9(H2W12O40)]·nH2O (Ln=EuIII (1), GdIII (2), DyIII (4), n=11; TbIII (3), n=12; L=pyridine-3,5-dicarboxylate dianion) have been synthesized in aqueous solution and characterized by element analysis, IR spectrometry and thermogravimetric analysis. Single-crystal X-ray diffraction analyses reveal these compounds are isostructural with a P21/n space group. The W12 cluster acting as a tridentate ligand connects three Ln3+ ions, in turn, each Ln2 ion links two W12 clusters, as a result, a W12–Ln polymeric chain is formed. Coordination of pyridine-3,5-dicarboxylate ligands to the Ln3+ ions leads to a Ln–L polymeric chain. The two chains, W12–Ln and Ln–L, share Ln2 ions, resulting in a 2-D layer. Ring coordination of pyridine-3,5-dicarboxylate and W12 to the Ln ions changes some bond angles of W12 that leads to a slight distortion of W12 and splitting of vibration band of W–Oc–W. Solid-state photoluminescence properties of compounds 1−4 have been investigated.