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

Abstract

Two novel polynuclear dysprosium (Dy)-containing polytungstoarsenates, CsK7Na16[(AsW9O33)6Dy6W10O24(H2O)23]·40H2O (1) and Cs2K18Na18[(AsW9O33)7Dy7W8O21(H2O)17(μ3-OH)(OH)]·78H2O (2), have been synthesized via the reaction of the preformed polyoxometalate (POM) precursor [As2W19O67(H2O)]14- and Dy3+ ions through controlling pH. The polyanion of 1 can be described as a dimer of two similar trimers {(AsW9O33)3Dy2W5O12(H2O)6} that are linked by Dy cation and two μ2-oxo groups, and the Dy(III) ions in 1 are arranged in a linear fashion. Compound 2 presenting an interesting W-shaped structure, assembly composed of a dimeric {(AsW9O33)2W3Dy2O8(H2O)7}, a trimer {(AsW9O33)3W4Dy2O11(OH)(H2O)3}, and a particular sandwiched {(AsW9O33)2WDy3O4(μ3-OH)(H2O)7} segment concatenated by μ2-oxo groups. The solid-state luminescence performances and lifetime decay behaviors of 1 and 2 were systematically researched at ambient temperature, and time-resolved fluorescence spectra of 1 and 2 indicate energy transfer (ET) from the photoexcitation O → M ligand to the metal charge-transfer (LMCT) bands of the POM ligands to Dy3+ ions. Moreover, the dynamic magnetic measurement indicates that 1 and 2 exhibit slow relaxation of the magnetization.