Multidimensional crystal frameworks based on heteropoly blue building block of [SiW10MoV2O40]6−: synthesis, structures and magnetic properties

Abstract

Four heteropoly blue complexes constructed from Keggin-type heteropoly blue molybdenum–tungsten clusters and Cu(II) ions as linkers, H₂[α-SiW₁₀Mo^V₂O₄₀][Cu(PDA)₂·H₂O]₂ (1), H₂[α-SiW₁₀Mo^V₂O₄₀][Cu(DEF)₃·H₂O][Cu(DEF)₂·2H₂O]·6H₂O (2), H₂[α-SiW₁₀Mo^V₂O₄₀][Cu(DMF)₃H₂O]₂·6H₂O (3), and H₄[α-SiW₁₀Mo^V₂O₄₀]₂[CuK₂(DMF)₆][Na_0.75K_3.25(DMF)₆] (4) [PDA = propanediamide, DEF = N,N-diethylformamide and DMF = N,N-dimethylformamide], have been synthesized by conventional reactions and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, thermogravimetry, X-ray powder diffraction (XRD) and UV spectra. The amount of Cu(II) and the nature of the ligand (DMF, DEF and PDA) can control both the linkage pattern of Cu(II) ions and the dimensionality of the frameworks; this demonstrates for the first time the possibility to assemble heteropoly blue architectures in different dimensionality ranging from zero-dimensional (0D) to one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D). The magnetic investigation showed that the positive magnetic moment could be observed at room temperature, which should be unusual results in magnetochemistry of the two-electron reduced heteropoly blue. The stability and formation conditions of the four compounds are also discussed.