Synthesis, Structure and Physical Properties of an Hybrid Compound Based on Strandberg Type Polyoxoanions and Copper Cations

Single crystals of novel Strandberg type molybdophosphonate complex, (C5H7N2)6[Cu(H2O)3HP2Mo5O23]2·4H2O, are synthesized in aqueous solution and characterized by X-ray diffraction, spectroscopy (diffuse reflectance, UV–Vis and IR) and thermal analysis. Single crystal X-ray diffraction analysis reveals that this novel compound is composed of [Cu(H2O)3HP2Mo5O23]3− anions, three distinct 2-aminopyridinium cations as counter-ions and two distinct crystallization water molecules. The crystal packing is stabilized by H-bonds and π–π interactions, resulting in a 3D framework. In addition, the magnetic behavior of the related compound is measured. Magnetic measurements from 100 to 2 K indicate the presence of an antiferromagnetic coupling between the Cu (II) ions in (C5H7N2)6[Cu(H2O)3HP2Mo5O23]2·4H2O complex, resulting in a maximum of an antiferromagnetic–paramagnetic transition at TN = 7 K. Magnetic susceptibility data indicate an antiferromagnetic Curie–Weiss behavior in the studied temperature range, and molecular field theory gives the (J/kB) values of the nearest neighbor interactions between copper ions.