title: Cobalt(II) octacyanotungstate(V) organic-inorganic hybrid ferromagnetic materials with pyrazine and 4,4'-bipyridine.
abstract: Two new ferromagnetic organic-inorganic hybrid materials [Co(II)3(H2O)6(pyz)3[W(V)(CN)8]2].3.5H2O (1) and [Co(II)3(H2O)4(4,4'-bpy)3[W(V)(CN)8]2].1.5(4,4'-bpy).6H2O (2) have been synthesised and characterised. The structure of the compounds have been investigated combining EXAFS (extended X-ray absorption fine structure), ES-MS (electrospray mass spectrometry), IR (infrared spectroscopy), UV-VIS electronic spectroscopy and TGA (thermogravimetric analysis) coupled with QMS (quadrupole mass spectrometer) experiments. The studies reveal that both compounds consist of Co(II)-NC-W(V) and Co(II)-L-Co(II) linkages (L = pyrazine (1) or 4,4-bipyridine (2)). Both networks are created by cyano-bridged Co(II)3W(V)2 chains joined by organic linkers into a 2D architecture. A difference of cobalt coordination numbers in both compounds derived from EXAFS study is consistent with the ES-MS conclusion. The ac magnetic characterisation exhibits the transition to the ferromagnetic phase at T(C) = 26 K (1) and to the spin glass-like phase at T(G) = 16 K (2). The frequency dependent chi'(T) and chi''(T) signals indicate the presence of some disorder in spin alignment below ordering temperatures. Both networks are also characterised a by magnetic hysteresis loop of coercive field H(c) = 750 Oe (1) and 1200 Oe (2) at T = 4.2 K.
authors.affiliation: Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060, Kraków, Poland. podgajny@chemia.uj.edu.pl
authors.forename: Robert
authors.initials: R
authors.lastname: Podgajny
authors.forename: Maria
authors.initials: M
authors.lastname: Bałanda
authors.forename: Marcin
authors.initials: M
authors.lastname: Sikora
authors.forename: Marta
authors.initials: M
authors.lastname: Borowiec
authors.forename: Leszek
authors.initials: L
authors.lastname: Spałek
authors.forename: Czesław
authors.initials: C
authors.lastname: Kapusta
authors.forename: Barbara
authors.initials: B
authors.lastname: Sieklucka