The compound (NH₄)₇[ V^vO₄W₁₀^VIV₂^VIO₃₆]·ca.22H₂O (1) has been synthesized from an aqueous ammonium acetate buffer (pH 4) containing sodium vanadate, sodium rungstate_and sodium dithionite. Compound (1) crystallizes in a cubic space groupFm — 3, witha = 22.2001(6) Å and Z = 8. The anion [V^vO₄W₁₀^VIV₂^IVO₃₆]^7- is a typical Keggin type structure with V^VO₄ as the central tetrahedron. (1) has further been characterized by elemental analyses, redox titration, IR, EPR, and electronic spectroscopy and room temperature magnetic moment measurement.

Synthesis and structural characterization of a polyoxometalate compound Na₃(H₂O)₆ [Al(OH)₆Mo₆O₁₈]-2H₂O (1) have been described. Compound1 exhibits three-dimensional network structure in the solid state, which is assembled by Anderson-type heteropolyanions, [Al(OH)₆Mo₆O₁₈]_n^3n-, as building blocks sharing sodium cations.1 possesses “sinuous” channels occupied by supramolecular water dimers as guests. Anderson anions, sodium-coordinated water and crystal water are additionally involved in an intricate hydrogen-bonding network in the crystal of1.

This article describes an account of some of our polyoxometalate (POM)-based research, we have been doing in our laboratory last several years. There are several well-defined POM cluster anions, that are structurally characterized. We have chosen Anderson-type of heteropolyanion [Al(OH)₆Mo₆O₁₈]$^{3−}$ and explored its linking propensity in different dimensions using `s', `d' and `f' block elements as linkers.We have demonstrated how a lanthanide linker provides a new pathway in forming a two-dimensional linked {As₈V₁₄} system [{Ln(H₂O)₆}₂As₈V₁₄O₄₂(SO₃)]$_n$.8nH₂O, that is derived from discrete {As₈V₁₄} cluster containing compound (NH₄)₆[As₈V₁₄O₄₂(SO₃)]. A polyoxometalate compound has been described in which a reduced tungstovanadate-heteropolyanion clusters get linked via capped V = O groups into one-dimensional chains. All these systems have already been reported elsewhere. The last portion of this article will be described by a new system [3-ampH]₆[V₁₀O₂₈]$\cdot$2H₂O having discrete molecular structure and extended supramolecular structure.

One-dimensional isomorphous inorganic polymers containing Anderson type heteropoly anion as a basic building unit, namely [La(H₂O)₇Cr(OH)₆Mo₆O₁₈]$_n$·4nH₂O (1), [Gd(H₂O)₇Cr(OH)₆Mo₆O₁₈]$_n$·4nH₂O (2), [Gd(H₂O)₇Al(OH)₆Mo₆O₁₈]$_n$·4nH₂O (3), and [Eu(H₂O)₇Al(OH)₆Mo₆O₁₈]$_n$·4nH₂O (4) have been synthesized and studied by the powdered X-ray diffraction, TGA, IR, electronic and ESR spectroscopy, and unambiguously by single crystal X-ray crystallography. Isomorphous compounds 1-4 are crystallized in orthorhombic system with $Pca2_1$ space group. The crystal structure analysis reveals a one-dimensional extended chain in which the Anderson type heteropolyanion, acting as the building unit, is linked by rare earth metal ions in a zig-zag fashion. In the crystal structure, all types of oxygens of the heteropolyanion, lattice waters, lanthanum coordinated waters are extensively involved in O—H…O hydrogen bonding interactions. Compounds are additionally characterized by UV-visible and ESR spectroscopy.

Diffusion of piperidine and pyridine into an acidified aqueous solution of Na₂MoO₄, yield compounds [(pipH)₄][Mo₈O₂₆] · 4H₂O (pip = piperidine = C₅H₁₁N) (1) and [(pyH)₄][Mo₈O₂₆] (py =pyridine = C₅H₅N) (2), respectively. Compound 1 possesses supramolecular 3-D network and the relevant connectivity pattern generates channels of approximate dimensions of 10.76 × 11.57´A^{° 2}, in which the piperidinium cations are located as guests. Multidimensional supramolecular frameworks (3-D in compound 1 and 2-D layer type of network in compound 2) have been made possible, as the organic cations and polyoxometalate (POM) anions are glued together by significant hydrogen bonding interactions. The synthesis of compounds 1 and 2 provides a unique ‘gas–liquid’ synthetic route in POM chemistry that result in organic–inorganic hybrid materials with structural diversities. This synthetic approach, first time in POM chemistry, can be described as a potential bag filter for volatile organic amines.