title: Synthesis, crystal structure, and magnetic properties of the coordination polymer [Fe(NCS)2(1,2-bis(4-pyridyl)-ethylene)]n showing a two step metamagnetic transition.
abstract: Reaction of iron(II) thiocyanate with an excess of trans-1,2-bis(4-pyridyl)-ethylene (bpe) in acetonitrile at room temperature leads to the formation of [Fe(NCS)(2)(bpe)(2)·(bpe)] (1), which is isotypic to its Co(II) analogue. Using slightly different reaction conditions the literature known compound [Fe(NCS)(2)(bpe)(2)(H(2)O)(2)] (2) was obtained as a phase pure material. Simultaneous differential thermoanalysis and thermogravimetry prove that the hydrate 2 transforms into the anhydrate [Fe(NCS)(2)(bpe)(2)] (3), that decomposes on further heating into the new ligand-deficient 1:1 compound of composition [Fe(NCS)(2)(bpe)](n) (4), which can also be obtained directly by thermal decomposition of 1. Further investigations reveal that 4 can also be prepared under solvothermal conditions, and single crystal structure analysis shows that the iron(II) cations are linked via μ-1,3 bridging thiocyanato anions into chains, that are further connected into layers by the bpe ligands. Magnetic measurements, performed on powder samples, prove that 1 and 2 show only Curie-Weiss behavior, whereas in 4 antiferromagnetic ordering with a Néel temperature of 5.0 K is observed. At T < 4.0 K a two-step metamagnetic transition occurs at applied magnetic fields of 1300 and 1775 Oe. The magnetic properties are discussed and compared with those of related compounds.
authors.affiliation: Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Strasse 2, D-24118 Kiel, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Wöhlert
authors.forename: Mario
authors.initials: M
authors.lastname: Wriedt
authors.forename: Tomasz
authors.initials: T
authors.lastname: Fic
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Tomkowicz
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Haase
authors.forename: Christian
authors.initials: C
authors.lastname: Näther