Abstract:

The structures of three new polymeric lanthanide complexes, poly[[bis-(2,2′-bipyridine)-μ4-itaconato-di-μ3-itaconato- digadolinium(III)] tetra-hydrate], {[Gd 2(C 5H 4O 4) 3(C 10H 8N 2) 2]̇4H 2O} n , (I),poly[diaqua-(2,2′- bipyridine)di-μ3-itaconato-μ2-ita-conato-digadolinium(III)], [Gd 2(C 5H 404) 3(C 10H 8N 2)(H 2O) 2] n , (II), and poly-[[bis-(2,2′-bipyridine)-μ4-itaconato-di-μ3-itaconato-di- holmium(III)] dihydrate], {[Ho 2(C 5H 4O 4) 3(C 10H 8N 2) 2]̇2H2O} 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 7N 2 environments, with both N-donor atoms in each provided by a chelating 2,2′-bipyridine (bpy) unit. The coord-inating O atoms are from three different itaconate (ita) anions (itaconic acid is 2-methyl-idene-butane-dioic acid). Compound (II) also presents two independent Gd centres (one ten- and the other ight-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 mol-ecules. In compounds (II) and (III), those ita anions bisected by a symmetry element incompatible with the inter-nal symmetry of the ligand exhibit disorder in the C=CH 2 group. © 2009 International Union of Crystallography.