Solid-state transformation of [Co(NCS)2(pyridine)4] into [Co(NCS)2(pyridine)2]n: from Curie–Weiss paramagnetism to single chain magnetic behaviour

Abstract

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 φ = 0.12 and an effective energy barrier (-U(eff)/k(B)) of 62.5 K for the spin relaxation.

Thiocyanato Coordination Polymers with Isomeric Coordination Networks – Synthesis, Structures, and Magnetic Properties

“…[56][57][58][59][60][61][62][63][64][65][66] In most cases, we crystallized structures in which the metal cations are linked by pairs of anionic ligands into chains.…”

catena-Poly[[bis(pyridine-κN)nickel(II)]-di-μ-thiocyanato-κ2N:S;κ2S:N]

“…For isotypic structures, see : Boeckmann & Nä ther (2010, 2012; Chen et al (2005). For a previous structure report of the title compound, see Reller & Oswald (1986).…”

Poly[(μ-1,3-thiocyanato-κN,S)(isonicotinato-κN,O)(ethanol-κO)cadmium(II)]

“…For general background information, including details of thermal decomposition reactions and magnetic properties, see: Nä ther & Greve (2003); Boeckmann & Nä ther (2010Wö hlert et al (2011). For related structures, see : Yang et al (2001).…”