Structural and Magnetic Studies of a New Co(II) Thiocyanato Coordination Polymer Showing Slow Magnetic Relaxations and a Metamagnetic Transition

• Published in: Inorganic chemistry 2013-11, Vol.52 (22), p.12947-12957
• Main Authors: Wöhlert, Susanne, Fic, Tomasz, Tomkowicz, Zbigniew, Ebbinghaus, Stefan G, Rams, Michał, Haase, Wolfgang, Näther, Christian
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic4012235

Reaction of Co(NCS)2 with 4-ethylpyridine leads to the formation of three new compounds of composition Co(NCS)2(4-ethylpyridine)4 (1), [(Co(NCS)2]2(4-ethylpyridine)6 (2), and [Co(NCS)2(4-ethylpyridine)2] n (3). In all compounds the coordination of the Co(II) ions is distorted octahedral. 1 consists of discrete monomeric complexes and in 2 two Co(II) cations are linked by pairs of μ-1,3-bridging thiocyanato ligands into dimers. In the crystal structure of 3 the Co(II) cations are connected into chains by the same bridge as in 2. Magnetic studies show that 1 and 2 are paramagnets down to a temperature of 2 K, while compound 3, which is the main object of this study, is an antiferromagnet with the Néel temperature T N = 3.4 K. Its magnetic structure is built from ferromagnetic chains, which are weakly antiferromagnetically coupled. With increasing magnetic field a metamagnetic transition starts at ∼175 Oe, as observed for a polycrystalline sample. Magnetic relaxations, which were observed in the antiferromagnetic state, are retained at the metamagnetic transition. With decreasing field 3 remains in a state, in which except of the faster magnetic relaxation process in single chains also a slower process coexists resulting in the appearance of a magnetic hysteresis loop.