title: Five related metal-organic frameworks constructed from [Ln2(SO4)2(H2O)n]2+ units and oxalate or acetate ligands.
abstract: We have synthesized a series of lanthanide-based metal-organic solids and characterized them through structural, magnetic and luminescence analyses. The nine compounds in the series NH(4)[Ln(SO(4))(H(2)O)(C(2)O(4))] [Ln = Ce, Nd, Eu, Gd (x2), Tb, Dy, Er, Yb] belong to four new three-dimensional (3D) structural groups, which we label CKMOF-4a, -4b, -5a, and -5b. The CKMOF-4a (Ce.) and -4b (Gd., Tb., Dy., Er., Yb.) structures feature [Ln(2)(SO(4))(2)(H(2)O)(2)](2+) units and C(2)O(4)(2-) ligands having the same symmetry operations, but their SO(4)(2-) anions feature different connective modes. These units are extended into one-dimensional ribbons fused together by oxalate ligands to form the two 3D open frameworks. The structures of CKMOF-5a (Nd.) and -5b (Eu., Gd.) comprise networks of c-glide-arranged [Ln(2)(SO(4))(2)(H(2)O)(2)](2+) units, in which the oxalate ligands are encapsulated within eight-membered rings. The networks are supported by distinct sites of oxalate ligands to form the two types of 3D open frameworks, the structural topologies of which are distinguished by the versatile connective modes of the SO(4)(2-) anions. The polymeric phases CKMOF-4b and -5b exist in the Gd analogues. For the Dy analogues, varying the size of the cation used as the template led to the selective precipitation of each of these two phases. The layer structure of [Gd(SO(4))(H(2)O)(2)(CH(3)CO(2))] (Gd.), labelled CKMOF-6, assembled from [Gd(2)(SO(4))(2)(H(2)O)(4)](2+) units and acetate ligands; the geometries of the [Gd(2)O(2)] rhombic units may induce ferromagnetic coupling at low temperature. Eu. and Tb. were luminescent, displaying red and green emissions, respectively.
authors.affiliation: Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan.
authors.forename: Hsiao-Chan
authors.initials: HC
authors.lastname: Liu
authors.forename: I-Han
authors.initials: IH
authors.lastname: Chen
authors.forename: Anny
authors.initials: A
authors.lastname: Huang
authors.forename: Sin-Chiang
authors.initials: SC
authors.lastname: Huang
authors.forename: Kuei-Fang
authors.initials: KF
authors.lastname: Hsu