Crystal and magnetic structure of the two-dimensional coordination polymers CoCl2(bpy-d8) and NiCl2(bpy-d8)

Neutron diffraction studies of polycrystalline samples of the two-dimensional coordination polymers CoCl2(bpy-d8) and NiCl2(bpy-d8) (bpy-d8=4,4'-bipyridine, fully deuterated) were carried out at various temperatures in order to determine their chemical and magnetically ordered structures. For both compounds, an orthorhombic structure, space group Pban (No. 50), was observed in which infinite chains of (-CoCl2-) or (-NiCl2-) units were cross-linked by the bipyridine ligands. Previous magnetic susceptibility studies of Co- and NiCl2(bpy) revealed long-range antiferromagnetic ordering below 5.0 and 8.5 K, respectively. From the low-temperature neutron diffraction data, a simple magnetic moment arrangement was deduced in which the metal ions are ferromagnetically coupled within the metal-chloride chains and nearest-neighbor chains couple antiferromagnetically. At 1.5 K, ordered moments of 2.8(2) and 2.0(2)μB, respectively, were observed with a moment orientation along the metal-bpy-metal bridges. (orig.)