Arsenicum-centered Molybdenum–Vanadium polyoxometalates bearing transition metal complexes: Hydrothermal syntheses, crystal structures and magnetic properties

Abstract

The tetra-capped Keggin anion-supported Cobalt–Phenanthroline complex [Co 2(phen) 2(OH) 2(H 2O) 4] 0.5[{Co(phen) 2(H 2O)} 2AsMo 6 VIMo 2 VV 8 IVO 44]·2H 2O ( 1) and the bicapped Keggin anion-based Nickel–phenanthroline compound [Ni(phen) 2H 2O] 2[AsMo 11 VIMo VO 40(V IVO 2) 0.5].2H 2O( 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(H 2O) 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 1 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).