Self-Assembled Tetrameric Lanthanide-Containing Germanotungstates [(Ln2GeW10O38)4(W3O8)(OH)4(H2O)2]26-: Syntheses, Crystal Structure, Photoluminescence and Electrochemical Properties.

A series of six lanthanide-containing germanotungstates of the formula: [(Ln(2)GeW(10)O(38))(4)(W3O8)(OH)(4)(H2O)(2)](26-) (Ln=Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6) have been synthesized under ambient conditions. The synthetic procedure involves the use of trilacunary Na-10[A-alpha-GeW9O34].16H(2)O as a preformed precursor along with lanthanide salts in 0.5 M potassium chloride solution. The interaction of the trilacunary Na-10[A-alpha-GeW9O34].16H(2)O with the lanthanide salts leads to the formation of a tetrameric structure with four [GeW10O36](8-) dilacunary Keggin units incorporating eight lanthanide ions and three additional tungsten atoms. All the polyanions were structurally characterized by Fourier-transform infrared spectroscopy (FT-IR), Single Crystal X-ray Diffraction (SC-XRD), UV/Visible spectroscopy, thermogravimetric analysis (TGA), electrochemistry, Electron-spray ionization mass spectroscopy (ESI-MS), Powder X-ray diffraction (PXRD) and photoluminescence. FT-IR spectroscopy reveals that all the polyanions are isomorphous and SC-XRD shows that all the polyanions are isostructural and crystalize in the triclinic crystal system with P1? space group. Some of the polyanions show good photoluminescence properties. The cyclic voltammograms (CVs) of all the six compounds exhibit the same shape, each being composed of a pronounced reduction wave.