Structures and magnetic properties of one-dimensional polymers constructed with copper(II) salts and pyridinecarboxamide-type ligands

Three complexes of the composition {[Cu(μ1,5-dca)2(mppca)2] · H2O}n (1), [Cu(μ1,5-dca)2(nppca)2]n (2) and [Cu(μ-Cl)2(mppca)2]n (3) (dca = dicyanamide, View the MathML sourceN(CN)2-; mppca = N-(4′-methylphenyl)-4-pyridinecarboxamide; nppca = N-(4′-nitrophenyl)-4-pyridinecarboxamide) have been synthesized and characterized by single crystal X-ray crystallography and magnetic susceptibility studies. Different supramolecular structures of the complexes have been constructed by different non-covalent motifs in the crystalline solids. In complex 1, adjacent copper(II) atoms are connected by double μ1,5-dca(end-to-end) bridges to form a chain-like structure. The chains are linked by π–π interactions and hydrogen bonds between the ligands and water molecules to form a 3D network. In complex 2, copper(II) atom has a coordination environment similar to 1, but water molecules have not been found. Weak C–H⋯N hydrogen bonding and π–π interaction yield a 3D supramolecular network which is different from that of complex 1. Complex 3 is a 1D polymeric chain in which Cu(II) ions are bridged by Cl−, and only CH/π interactions had been found. Magnetic measurements revealed antiferromagnetic properties of 1, 3 and ferromagnetic behavior of 2.