Hydrothermal synthesis, crystal structures, and properties of two 3-D network nickel nicotinate coordination polymers: [Ni4(μ-H2O)2(nicotinate)8 · 2H2O] and [Ni2(H2O)2(nicotinate)4(4,4′-bpy)]

The three-dimensional coordination polymers [Ni4(μ-H2O)2(nic)8 · 2H2O] (nic = nicotinate, 3-pyridylcarboxylate) (1) and [Ni2(H2O)2(nic)4(4,4′-bpy)] (2) were prepared by the hydrothermal reaction of nickel(II) chloride, nicotinic acid, sodium hydroxide and an organoimine (several choices for 1, 4,4′-bipyridine for 2). The non-centrosymmetric crystal structure of 1 is constructed from binuclear [Ni2(μ-H2O)(μ3-nic)2]2+ subunits joined into 3-D via μ2- and μ3-nicotinate ligands, forming “bird”-shaped cavities that contain water molecule dimers. The crystal structure of 1 is compared and contrasted to two previously reported nickel(II) nicotinate phases. In contrast, the crystal structure of 2 is assembled from neutral [Ni(H2O)(μ2-nic)2] layers, connected into 3-D via tethering 4,4′-bpy moieties. 1 exhibits weak antiferromagnetic coupling across its binuclear subunits (J = −1.61(2) cm−1 for g = 2.233(2)), although anisotropy due to single-ion zero-field-splitting (D) cannot be excluded. The 3-D structures of 1 and 2 remain stable above 300 °C and 200 °C, respectively.

The three-dimensional coordination polymers [Ni4(μ-H2O)2(nic)8 · 2H2O] (nic = nicotinate) (1) and [Ni2(H2O)2(nic)4(4,4′-bpy)] (2) were prepared via hydrothermal synthesis. The non-centrosymmetric crystal structure of 1 is constructed from binuclear [Ni2(μ-H2O)(μ3-nic)2]2+ subunits joined into 3-D by μ2-nic and μ3-nic moieties, forming “bird”-shaped cavities. In contrast, the crystal structure of 2 is assembled from neutral [Ni(H2O)(μ2-nic)2] layers, connected into 3-D via tethering 4,4′-bpy moieties. Magnetic and thermal properties are discussed.Figure optionsDownload as PowerPoint slide