The crystal structure and magnetic properties of the 1-dimensional dihalide-bridged polymers dichlorobis(thiazole)cobalt(II) and dibromobis(thiazole)-cobalt(II)

The isostructural polymeric compounds Co(thiazole)₂X₂ (X=Cl (1), Br(2)) have been synthesised by the addition of thiazole to an ethanolic solution of the corresponding anhydrous cobalt halide. Powder X-ray and neutron diffraction measurements were used for structural determination. The structures were determined using powder neutron diffraction data and Rietveld techniques: (1) C2/c, a=17.806(2) Å, b=3.6806(6) Å, c=14.807(3) Å, β=94.78(1)°, V=967.1(3) ų, Z=4; (2) C2/c, a=18.079(3) Å, b=3.8138(8) Å, c=15.022(4) Å, β=92.71(1)°, V=1034.6(4) ų, Z=4. Each linear polymer chain is composed of pseudo-octahedral, high-spin Co²⁺ centres, doubly linked by halide bridges. Magnetisation measurements of 1 and 2 at 5 K between 0 and 10 kG reveals a metamagnetic transition between antiferromagnetic and ferromagnetic states. Low temperature susceptibility data have been fitted to a one-dimensional Ising model with a mean field correction and were found to be anisotropic with ferromagnetic intrachain interactions along the b-axis and weaker antiferromagnetic interchain interactions.