pH-Controlled Assembly of Two Polynuclear Dy(III)-Containing Polytungstoarsenates with Magnetic and Luminescence Properties.

Two novel polynuclear dysprosium (Dy)-containing polytungstoarsenates, CsKNa[(AsWO)DyWO(HO)]·40HO () and CsKNa[(AsWO)DyWO(HO)(μ-OH)(OH)]·78HO (), have been synthesized via the reaction of the preformed polyoxometalate (POM) precursor [AsWO(HO)] and Dy ions through controlling pH. The polyanion of can be described as a dimer of two similar trimers {(AsWO)DyWO(HO)} that are linked by Dy cation and two μ-oxo groups, and the Dy(III) ions in are arranged in a linear fashion. Compound presenting an interesting W-shaped structure, assembly composed of a dimeric {(AsWO)WDyO(HO)}, a trimer {(AsWO)WDyO(OH)(HO)}, and a particular sandwiched {(AsWO)WDyO(μ-OH)(HO)} segment concatenated by μ-oxo groups. The solid-state luminescence performances and lifetime decay behaviors of and were systematically researched at ambient temperature, and time-resolved fluorescence spectra of and indicate energy transfer (ET) from the photoexcitation O → M ligand to the metal charge-transfer (LMCT) bands of the POM ligands to Dy ions. Moreover, the dynamic magnetic measurement indicates that and exhibit slow relaxation of the magnetization.