Solid-state transformation of [Co(NCS)2(pyridine)4] into [Co(NCS)2(pyridine)2]n: from Curie-Weiss paramagnetism to single chain magnetic behaviourElectronic supplementary information (ESI) available: Experimental and calculated X-ray powder pattern for compound [Co(NCS)2(pyridine)4] (1), IR-spectra of compounds [Co(NCS)2(pyridine)4] (1) and [Co(NCS)2(pyridine)2]n (2) and plots of in-phase χM′ and out-of-phase χM′′ AC magnetic susceptibility as a function of frequency for 2. CCDC reference number

• Main Authors: Boeckmann, Jan, Näther, Christian
• Format: Journal Article
• Language: English
• Published: 09.11.2010
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c0dt00904k

Reaction of Co(NCS) 2 with pyridine (pyr) in aqueous solution at room temperature leads to the formation of the pyridine-rich 1 : 4 compound of composition [Co(NCS) 2 (pyridine) 4 ] ( 1 ) reported recently. On heating, the pyridine-rich 1 : 4 compound transforms into its corresponding pyridine-deficient 1 : 2 compound of composition [Co(NCS) 2 (pyridine) 2 ] n ( 2 ), which decomposes on further heating. In the crystal structure of compound 2 the metal cations are coordinated by four N-atoms of two pyridine ligands and two N-bonded thiocyanato anions, each in mutually trans orientation, and by two S-atoms of two adjacent thiocyanato anions in a slightly distorted octahedral geometry. The thiocyanato anions bridge the metal cations forming one-dimensional polymeric chains. IR spectroscopic investigations on the pyridine-deficient 1 : 2 compound prepared in thermal decomposition are in accordance with bridging thiocyanato anions. Magnetic measurements of the pyridine-rich 1 : 4 compound and pyridine-deficient 1 : 2 compound reveal different behaviour with Curie-Weiss paramagnetism for compound 1 and single chain magnetic behaviour for compound 2 , with a Mydosh-parameter = 0.12 and an effective energy barrier (− U eff / k B ) of 62.5 K for the spin relaxation. Thermal transformation of the pyridine-rich precursor [Co(NCS) 2 (pyridine) 4 ] leads to the formation of the pyridine-deficient intermediate of composition [Co(NCS) 2 (pyridine) 2 ] n . Magnetic measurements for the latter compound show single chain magnetic behaviour, whereas the discrete precursor only shows Curie-Weiss behaviour.