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A sandwiched‐type carbonate‐encapsulated yttrium‐containing arsenotungstate(III) has been synthesized under mild reaction conditions. The polyanion [NaCH3COO{Y2(H2O)3(B‐α‐AsW9O33)2(W2O5)(CO3)}]12− (1) was isolated as a solid crystalline material by the reaction of a YIII salt with the sodium salt of trilacunary [AsW9O33]9− in sodium acetate solution. The sodium salt of the polyanion, i.e. Na12[Na(CH3COO){Y2(AsW9O33)2(W2O5)(CO3)(H3O)3}]·22H2O (1a), was characterized by various analytical techniques, such as FT–IR, single‐crystal X‐ray diffraction (SC–XRD), TGA (thermogravimetric analysis), 13C NMR and ESI–MS (electrospray ionization mass spectrometry). SC–XRD studies revealed that the polyanion crystallizes in the triclinic space group P. The structure showed that the polyanion is a carbonate‐encapsulated sandwich‐type species, consisting of two trilacunary B‐α‐[AsW9O33]9−, with a lone‐pair‐containing AsIII heteroatom, together with two extra tungsten centres and two yttrium cations at the sandwich position, where CH3COO− and Na+ ions act as linkers between the two polyanion units. In addition, we have also synthesized two carbonate‐encapsulated germanotungstates(IV), without lone‐pair‐containing heteroatoms, with the formula [Ln3(A‐β‐GeW9O34)2(CO3)(H2O)3]13− [Ln = YIII (2) and YbIII (3)], i.e. Y2K3Na4[Y3(A‐β‐GeW9O34)2(CO3)(H2O)3]·19H2O (2a) and YbK8Na2[Yb(A‐β‐GeW9O34)2(CO3)(H2O)3]·16H2O (3a), and characterized them by FT–IR, SC–XRD, TGA and ESI–MS. Here, the lanthanide ions act as linkers, extending the structures into higher dimensions. Sodium and potassium ions also play a key role as linkers, further extending the structure. The packing shows the presence of certain hydrophilic pores within the structure.

A series of six lanthanide‐containing germanotungstates of the formula: [(Ln2GeW10O38)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 Na10[A‐α‐GeW9O34]⋅16H2O as a preformed precursor along with lanthanide salts in 0.5 M potassium chloride solution. The interaction of the trilacunary Na10[A‐α‐GeW9O34]⋅16H2O 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.

A series of 12 inorganic–organic hybrid 4f-substituted arsenotungstates decorated with 3d-based complexes along with acetate bridging, viz. {[Cu2(H2O)(1,10-phen)2(μ-CH3COO)2]4[Ln2(H2O)2(μ-CH3COO)2(α-AsW11O39)2]}2− (LnIII = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), have been synthesized. These compounds were isolated using a one-pot synthetic strategy with copper, lanthanoid, trilacunary arsenotungstate and 1,10-phenanthroline as precursors. They were characterized using various analytical techniques, such as single-crystal X-ray diffraction (SC-XRD), powder XRD (PXRD), Fourier transform IR (FT–IR) spectroscopy, UV–Vis spectroscopy and thermogravimetric analysis (TGA). In all these compounds, a dinuclear Ln2(ac)2 moiety is sandwiched between two monolacunary [AsW11O39]7− polyoxometalates (POMs), where the Ln2(ac)2 moiety is comprised of two acetate ligands in a μ-κO,O′:κO fashion. Moreover, the anion is decorated by a copper–phenanthroline–acetate complex through a terminal O atom of the polyanion.

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