Arsenicum-centered molybdenum-vanadium polyoxometalates bearing transition metal complexes: Hydrothermal syntheses, crystal structures and magnetic properties

The tetra-capped Keggin anion-supported Cobalt-Phenanthroline complex [Co-2(phen)(2)(OH)(2)(H2O)(4)](0.5)[{Co(phen)(2)(H2O)}(2)(AsMo6Mo2)-Mo-VI (V)A(8)(IV)O(44)]center dot 2H(2)O (1) and the bicapped Keggin anion-based Nickel-phenanthroline compound [Ni(phen)(2)H2O](2)[(AsMo11MoO40)-Mo-VI-O-V((VO2)-O-IV)0.5]. 2H(2)O(2), have been hydrothermally synthesized and structurally characterized by elemental analyses, single crystal X-ray diffraction, IR and X-ray photoelectron spectrum. The interesting structural feature of 1 is that there are two types of free complex cation [Co-2(phen)(2)(OH)(2)(H2O)(4)](2+) in different orientations in the crystal structure of 1, and these free complex cations coexist in the space between polyoxometalate clusters. The structure of compound 2 is very like compound 1 except that the Keggin unit is bi-capped instead of tetra-capped. Compounds 1 and 2 are examples that Arsenicum-centered vanadomolybdate anion acts as an active building block in the fabrication of polyoxometalates-supported hybrid solids. Then, the magnetic characteristic of I is typical of a dominant ferromagnetic interactions in the 6-300 K temperature range and a succedent antiferromagnetic interactions in the very low temperature range (2-6 K), while the magnetic behavior for 2 is characteristic of a dominant ferromagnetic interactions in the 6-300 K temperature range and succedent antiferromagnetic interactions in the very low temperature range (2-6 K). (c) 2005 Elsevier B.V. All fights reserved