Synthesis and crystal structures of a series of complexes based on a rigid angular ligand and the magnetic properties of the Cu(ii) polymer

Abstract

Treatment of 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpodz) with AgNO₃, Cu(OAc)₂, CoSO_4, CdI₂ or MnSO₄ afforded five complexes, the coordination polymers [Ag(bpodz)(μ-NO₃)]_n (1), {[Cu₂(bpodz)(μ-OAc)₄](CH₃OH)₂}_n (2), {[Co(bpodz)(SO₄)(H₂O)₃](CH₃OH)₂}_n (3) and [Cd(bpodz)₂(μ-I)₂]_n (4), and the complex [Mn(bpodz)₂(SCN)₂(H₂O)₂] (5). These compounds have been structurally characterized by X-ray single crystal diffraction. 1 is a 2-D network polymer constructed by ladder-like chains. In these chains, the nitrate anions are shared by two silver(I) to form a rhombic Ag₂O₂ plane. Polymer 2 is a 1-D wave-like chain in which the copper(II) atoms bridged by the acetate groups are separated by a distance of 2.623 Å. Polymer 3 shows a 1-D linear structure, in which interchain H-bonding interactions contribute to the final 2-D networks. Polymer 4 crystallizes as infinite CdI₂ chains in which cadmium(II) ions are doubly bridged by pairs of iodine atoms; the bpodz complete the octahedral coordination of the cadmium atoms, but act as monodentate ligands so do not to link the CdI₂ chains to form extended 2-D layers. Complex 5 is constructed into a 2-D stair-like structure through hydrogen bonds. Magnetic susceptibility data for polymer 2, measured from 5 to 300 K, show strong antiferromagnetic coupling. These data were fitted to the appropriate equations derived from the Hamiltonian H = −2JS₁S₂, giving the parameter −2J = 320 cm⁻¹.