Two new inorganic-organic hybrid materials based on heteropolyoxometalates, (C₄H₁₀N)₆ (P₂ Mo₁₈O₆₂).4H₂O I, and (C₄H₁₀N)₆ (As₂Mo₁₈O₆₂).4H₂O II, where C₄H₁₀N is protonated pyrrolidine have been synthesized and structurally characterized by physic-chemical methods. Single-crystal X-ray diffraction method, infrared, ultraviolet spectroscopy, Thermogravimetricanalysis andcyclic voltammetry measurements of the title hybrid materials indicate that there are hydrogen bond interaction between O atoms of the hetero-polyoxometalates and water molecules as well as the N and O atoms of the organic compound. The molecular structures of synthesized hybrid materials contain discrete entities of pyrrolidinumion and water molecules surround every [X₂Mo₁₈O₆₂]⁶⁻ anion over the extended crystalline network that the [X₂Mo₁₈O₆₂]⁶⁻ anion retains its ``Dawson structure". Crystal data: I monoclinic, space group P2₁/a, a = 13,453(1) Å, b = 24,046 (1) Å, c = 24,119(1) 𝛽 = 97, 99(1)°, V = 7726,30(5) ų and Z = 4; II monoclinic, space group P2₁/a, a = 13.4900(1) Å, 24.0900(1) Å, 24.2740(1) Å, 𝛽 = 98.320(1)°, V = 7805.40(7) ų and Z = 4.

A new octa-molybdate formulated as (C₂H₆N₄)₂ [β-Mo₈O₂₆].4H₂O (1) has been isolated by conventional solution method and structurally characterized by single-crystal X-ray diffraction method, IR spectroscopy, UV-Vis absorption, thermogravimetric analysis and cyclic voltammetry. Compound 1 crystallizes in the Triclinic system, space group P-1 with unit cell dimensions, a = 8.348 (2)Å, b = 10.154 (2)Å, c = 10.823 (3)Å, α = 68.35◦ (2), β = 71.59◦ (2), γ= 78.55◦ (2), V = 805.5 (3)ų, and Z = 2. The crystal structure of 1 is built up from octa-molybdate [β-Mo₈O₂₆]⁴⁻ clusters connected through hydrogen-bonding interactions into a three-dimensional supramolecular network.

The reaction of molybdic acid, phosphoric acid and copper(II) sulfate pentahydrate with m-toluidine in aqueous solution at room temperature furnished a new diphosphopentamolybdate (C ₇H ₁₀N) ₄ [H ₂P ₂Mo ₅O ₂ ₃] · H ₂O (1). A single-crystal X-ray diffraction study showed that the compound crystallizes in the triclinic crystal system with space group P − 1 and unit cell constants, a = 12.833 (3) Å, b = 13.9855 (4) Å, c = 14.9446 (4) Å, α = 64.607 (3)◦, β = 70.578 (2)◦, γ = 65.713 (3)◦. The sample was also analyzed by energydispersive spectroscopy (EDS), infrared spectroscopy (IR) andUV-visible spectroscopy. Using the refined atomic structure, Hirshfeld surface analysis and Semi-empirical calculations were performed to study the intermolecularinteractions and calculate theoretical properties of 1.