Molecular assemblies based on tricyanomethanide units and copper(II) ions

New co-ordination polymers of formulae [Cu(tcm)2(tn)] (1) and [Cu(tcm)(tn)2](tcm) (2) (tcm−=tricyanomethanide and tn=1,3-diaminopropane) have been synthesised and characterised by X-ray crystallography and magnetic measurements. For compound 1, the Cu(II) ion presents an elongated and distorted CuN4N1N1 octahedron generated by one chelating tn ligand and by four μ2-bridging tcm− ligands. The molecular arrangement of 1 can be described as a monodimensional chain of a ladder-like structure in which the Cu⋯Cu distance (7.5157(4) Å) through the tcm− ligand forming the sides is significantly shorter than the corresponding distance observed through that providing the rung (7.7455(4) Å). For compound 2, the Cu(II) ion presents a centrosymmetric elongated CuN4N2 octahedron; the equatorial plane is generated by two chelating tn ligands and the two axial positions are filled by two weakly co-ordinated equivalent tcm− units acting as μ2-bridging ligands. This leads to a monodimensional polymer in which the intrachain Cu⋯Cu distance is 9.1062(2) Å. Magnetic measurements, performed in the temperature range 2–300 K for both compounds, show weak antiferromagnetic interactions for compound 1 while compound 2 obeys a Curie law. The difference between the magnetic behaviours can be explained from the larger intrachain Cu⋯Cu separation in 2 than in 1.