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 [Ni-4(mu-H2O)(2)(nic)(8) center dot 2H(2)O] (nic = nicotinate, 3-pyridylcarboxylate) (1) and [Ni-2(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 [Ni-2(mu-H2O)(mu(3)-nic)(2)](2+) subunits joined into 3-D via mu(2)- and mu(3)-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)(mu(2)-nic)(2)] layers, connected into 3-1) 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 degrees C and 200 degrees C, respectively. (c) 2006 Elsevier Ltd. All rights reserved.