Two polyoxometallate-based supra­molecular compounds influenced by the ratio between the polyoxometallate anion and organic cation

Two polyoxometallate-based compounds, tris­[1,1'-(butane-1,4-di­yl)bis­(1H-imidazol-3-ium)] bis­[tetra­cosa-[mu]₂-oxido-do­deca­­oxido-[mu]₁₂-phosphato-dodeca­molybdenum(VI)], (C₁₀H₁₆N₄)₃[PMo₁₂O₄₀]₂, (I), and 1,1'-(butane-1,4-di­yl)bis­(1H-imid­azol-3-ium) 1-[4-(1H-imidazol-1-yl)but­yl]-1H-imidazol-3-ium tetra­cosa-[mu]₂-oxido-dodeca­oxido-[mu]₁₂-phosphato-dodeca­molyb­denum(VI) dihydrate, (C₁₀H₁₆N₄)(C₁₀H₁₅N₄)[PMo₁₂O₄₀]·2H₂O, (II), were synthesized by hydro­thermal techniques at different pH values. The stoichiometric ratio between the polyoxometallate (POM) anions and organic cations is 2:3 in (I), with one of the cations lying on an inversion centre. The doubly protonated 1,1'-(butane-1,4-di­yl)di­imidazole (BIM) cations are linked to the [PMo₁₂O₄₀]^3- anions by hydrogen bonds to form a three-dimensional supra­molecular network. The stoichiometric ratio of POM anions and organic cations is 1:2 in (II), and the anion is located about a centre of inversion. The partly protonated BIM cations and solvent water mol­ecules form hydrogen bonds with the [PMo₁₂O₄₀]^3- anions, yielding a two-dimensional supra­molecular layer. The different lattice architectures of (I) and (II) may be governed by the ratio between the POM anions and organic cations, which, in turn, is determined by the pH value.