Two dysprosium-incorporated tungstoarsenates: synthesis, structures and magnetic properties

Abstract

Two dysprosium-containing tungstoarsenates [C(NH₂)₃]₁₁[Dy₂(Hcit)₂(AsW₁₀O₃₈)]·9H₂O (1) and K_8−nH_3−n[Dy_3−nK_n(H₂O)₃(CO₃)(A-α-AsW₉O₃₄)(A-β-AsW₉O₃₄)]·22H₂O (n = 0 or 1) (2) have been synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, thermogravimetric analyses and infrared spectroscopy. Compound 1 is a citrate-decorated Keggin type di-substituted Ln/POM derivative with the two non-adjacent substituted sites occupied. Compound 2 is composed of two different trivacant Keggin unit isomers [A-α-AsW₉O₃₄]⁹⁻ and [A-β-AsW₉O₃₄]⁹⁻, linked to each other via one {Dy_3−nK_n(H₂O)₃(CO₃)}^{(7 − 2n)+} (n = 0 or 1) unit, where CO₃²⁻ is encapsulated in the triangle plane, resulting in a stable dysprosium carbonate-containing sandwich-type polyoxoanion with D_2h symmetry. The investigation on both static and dynamic magnetic properties of 1 and 2 show that the magnetic relaxation behavior of 2 appear in a static magnetic field of 5000 Oe, while 1 shows no positive out-of-phase ac susceptibility.