Ligand-Directed Assembly of Azide-Bridged Tetranuclear, One-Dimensional and Two-Dimensional Cu(II) Complexes: Synthesis, Crystal Structure and Magnetic Properties

Three Cu­(II) complexes of tetranuclear [Cu4(cmpy)4(N3)5Cl3] (1), 1D chain [Cu2(cea)2(N3)4]n (2), and two-dimensional layer [Cu5(cmpy)2(N3)10]n (3) were synthesized by controlling the molar ratio of Cu­(ClO4)2·6H2O, pyCH2Cl·HCl (cmpy·HCl), or H2NCH2CH2Cl·HCl (cea·HCl) and sodium azide. For complexes 1–3, the atom Cl of the ligands (cmpy and cea) is located at the Jahn–Teller axis of Cu­(II) with the weak Cu–Cl separations of 2.920(1) - 3.177(1) Å that are shorter than the sum of van der Waals radii of Cu and Cl atoms, 3.3 Å. The azide ligands coordinate to Cu­(II) in the equatorial or basal plane of the coordination pyramid, favoring strong magnetic coupling. The bridging angles of Cu–Nazido–Cu in complexes 1–3 are nearly 101°, corresponding to the presence of global ferromagnetic coupling. The end-to-end azide bridges appear exclusively in complex 3, linking the end-on azide-bridged 1D chains into a 2D layer.