Erbium fumarate [Er2(fum)3(H2O)4]·8H2O, 1, (fum = fumarate dianion) crystallizes at room temperature in a silica gel column. The structure is three-dimensional and consists of layers of erbium fumarate pillared
by fumarate dianions acting in the bis-chelating mode. The layers contain arrays of erbium cations bridged by
fumarate dianions acting in the bis-bidentate bridging mode. The relatively large channels formed in the direction
of the a and c axes are filled by water molecules that form a hydrogen bonded layer, comprising cyclic hexamers
with both boat and chair conformations and cyclic decamers with boat−chair−boat conformation. The water molecules
are reversibly removed at 90 °C. The evacuated metal−organic framework, 2, is stable up to 400 °C. Both compounds
1 and 2 exhibit weak antiferromagnetic interactions.
Thiocyanatonickel(II) and thiocyanatocobalt(II) complexes of the composition Ni(NCS)(2)(HIm)(2) (1) and Co(NCS)(2)(HIm)(2) (2), where HIm = imidazole, were prepared and studied. In particular, the crystal structure of Ni(NCS)(2)(HIm)(2) was determined by X-ray methods. This compound crystallizes in the monoclinic system, space group P2(1)/n, with a = 7.720(1) A, b = 5.557(1) A, c = 13.774(3) A, beta = 102.54(3) degrees, and Z = 2. Its structure consists of a one-dimensional polymeric chain in which nickel(II) ions are bridged by two thiocyanate groups bonding in an end-to-end fashion in a trans arrangement. The Ni...Ni distance is 5.557(1) A. The crystal packing is determined by the intermolecular hydrogen bonds and ring-stacking interactions. From their X-ray powder-diffraction patterns and IR spectra, the complexes 1 and 2 were found to be mutually isomorphous. The coordination compounds were identified and characterized using elemental analysis, magnetic measurements, and infrared and ligand-field spectra. Both complexes are first examples of ferromagnetically coupled one-dimensional polymeric compounds with double end-to-end thiocyanate bridges. The magnetic properties of the title compounds were investigated over the 1.9-290 K temperature range. The compounds exhibit long-range magnetic ordering with T(c) equal to 5.0 and 5.5 K for 1 and 2, respectively. Their isothermal magnetization was also studied. The magnetostructural properties of the nickel(II) compound obtained are discussed and compared to those of other double end-to-end thiocyanate-bridged nickel(II) complexes.
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