title: Synthesis, structure and magnetism of a new dimeric silicotungstate: K9Na2CU0.5[gamma-Cu2(H2O)SiW8O31]2.38H2O.
abstract: A new structurally distinct dimeric silicotungstate K9Na,Cu0.5[gamma-Cu2(H2O)SiWO31]2.38H2O (1) has been synthesized and characterized by infrared spectroscopy, elemental analysis, and variable-temperature magnetic measurements. Blue needle-like crystals of 1 were obtained by reaction of K8[gamma-SiW10O36] with 2 equivalents of Cu(n) in a 0.5 M sodium acetate solution (pH 4.2) and subsequent addition of an equal volume of ethylene glycol. The structure of 1 was determined by single-crystal X-ray diffraction: final R1 = 3.41% based on 9709 independent reflections. The structure consists of two [gamma-Cu2(H2O)SiWsO3,1]6- Keggin-like units with the [Cu2O(H2O)(micro3-O)(micro2-O)] moiety of one unit bonded to the top of a [W2O6] moiety of the other unit. Magnetic susceptibility measurements indicate competing ferro- and antiferromagnetic intramolecular coupling between the four S = 1/2 Cu(II) centers in the cluster anion.
authors.affiliation: Department of Chemistry, Emory, University, Atlanta, GA, 30322, USA.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Luo
authors.forename: Paul
authors.initials: P
authors.lastname: Kögerler
authors.forename: Rui
authors.initials: R
authors.lastname: Cao
authors.forename: Imroz
authors.initials: I
authors.lastname: Hakim
authors.forename: Craig L
authors.initials: CL
authors.lastname: Hill