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 [Cu-4(cmpy)(4)(N-3)(5)Cl-3] (1), 1D chain [Cu-2(cea)(2)(N-3)(4)](n) (2), and two-dimensional layer [Cu-5(cmpy)(2)(N-3)(10)](n) (3) were synthesized by controlling the molar ratio of Cu(ClO4)(2)center dot 6H(2)O, pyCH(2)Cl center dot HCl (cmpy center dot HCl), or H2NCH2CH2Cl center dot HCl (cea center dot 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) angstrom that are shorter than the sum of van der Waals radii of Cu and Cl atoms, 3.3 angstrom. 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-N-azido-Cu in complexes 1-3 are nearly 101 degrees, 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 ID chains into a 2D layer.