Abstract
The structures of three new polymeric lanthanide complexes, poly[[bis(2,2'-bipyridine)-mu(4)-itaconato-di-mu(3)-itaconato-digadolinium(III)] tetrahydrate], {[Gd(2)(C(5)H(4)O(4))(3)(C(10)H(8)N(2))(2)].4H(2)O}(n), (I), poly[diaqua(2,2'-bipyridine)di-mu(3)-itaconato-mu(2)-itaconato-digadolinium(III)], [Gd(2)(C(5)H(4)O(4))(3)(C(10)H(8)N(2))(H(2)O)(2)](n), (II), and poly[[bis(2,2'-bipyridine)-mu(4)-itaconato-di-mu(3)-itaconato-diholmium(III)] dihydrate], {[Ho(2)(C(5)H(4)O(4))(3)(C(10)H(8)N(2))(2)].2H(2)O}(n), (III), have been solved from twinned specimens. Compound (I) presents a two-dimensional polymeric structure parallel to (011) built up around two independent nine-coordinated Gd centres displaying similar GdO(7)N(2) environments, with both N-donor atoms in each provided by a chelating 2,2'-bipyridine (bpy) unit. The coordinating O atoms are from three different itaconate (ita) anions (itaconic acid is 2-methylidenebutanedioic acid). Compound (II) also presents two independent Gd centres (one ten- and the other eight-coordinated), but the overall formula and individual coordinations are different from those of (I). The chemical unit is in this case completed by one bpy ligand, three ita anions (one of them displaying a new, hitherto unreported, mu(3)-O,O':O',O'':O''' binding mode) and two aqua ligands. The whole structure is built up around a twofold rotation axis passing through both cations, as well as through the centre of the bpy ligand and one of the ita anions, thus making only half of the chemical unit independent. Finally, compound (III) presents a single independent Ho centre, a bpy unit and one and a half ita anions (one of them bisected by a twofold rotation axis) in the asymmetric unit, plus two (disordered) nonbonded solvent water molecules. In compounds (II) and (III), those ita anions bisected by a symmetry element incompatible with the internal symmetry of the ligand exhibit disorder in the C=CH(2) group.
Highlights
The generation of high-dimensional coordination polymers assembled from metal–organic compounds and characterized by open frameworks has been an important branch of crystal engineering, due to the expected potential properties of the eventual novel compounds, e.g. catalysis (Seo et al, 2000), ionexchange (Yaghi et al, 1997), gas absorption (Yaghi et al, 2003), and so on
The whole structure is built up around a twofold rotation axis passing through both cations, as well as through the centre of the bpy ligand and one of the ita anions, making only half of the chemical unit independent
Compound (III) presents a single independent Ho centre, a bpy unit and one and a half ita anions in the asymmetric unit, plus two nonbonded solvent water molecules
Summary
All content following this page was uploaded by M. It presents a two-dimensional polymeric structure built up around two independent Gd centres displaying similar GdO7N2 environments, with both N-donor atoms in each provided by a chelating bpy unit. The structure presents a single independent cation (Ho1), a bpy unit and one and a half ita anions in the asymmetric unit, plus one nonbonded solvent water molecule (disordered into two sites), stabilizing the structure These entities are disposed around a centre of symmetry as dimeric units of general formula [Ho2(ita)3(bpy)2]Á2H2O, the cation being eight-coordinated by a chelating bpy and two chelating carboxylate groups from an ita unit and its [010] translational image (coordination mode 4), generating a chain structure along the b axis, similar to (I).
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