Tetranuclear Copper(II) Complexes Bearing Cu4O6 and Cu4O4 Cores: Synthesis, Structure, Magnetic Properties, and DFT Study

The reaction of Cu(ClO4)(2)center dot 6H(2)O with N4O3 coordinating heptadentate (H3L1) and N2O coordinating tridentate reduced Schiff base (HL2) ligands yielded copper(II) tetra-nuclear complexes [Cu-4(L-1)(2)](ClO4)(2) (1) and [Cu-4(L-2)(4)](ClO4)(4) (2), respectively. Complex 1 crystallizes in the cubic system, space group Fd (3) over barc, with unit-cell parameters a = b = c = 43.124(5) angstrom, Z = 48, whereas complex 2 crystallizes in the space group P4(1)2(1)2 in the tetragonal crystal system with Z = 8 and unit-cell parameters a = b = 17.1.13(4) angstrom, c = 44.150(4) angstrom. The X-ray structures of 1 and 2 have revealed a Cu4O6 core in I and a Cu4O4 core in 2. Complexes 1 and 2 show intramolecular antiferromagnetic interaction with moderate vertical bar J vertical bar values (104.2 cm(-1) for 1 and 155.1 cm(-1) for 2). The moderate vertical bar J vertical bar value can be explained by the existence of only one bridging alkoxido group between each pair of copper(II) atoms and the out-of-plane displacement of the alkoxido carbon atom from the Cu-O-Cu plane, Broken-symmetry density functional theory (BSDFT) has been used to justify the exchange pathways.