Synthesis, crystal structures, spectroscopic and electrochemical studies on Cu(II) and Ni(II) complexes with compartmental nitrogen-oxygen mixed donor ligands

The synthesis and characterization of two new N2O4 donor type ligands, 2-{[(2-(3-[2-({[(2-hydroxy-phenyl)methylidene]amino)methyl)phenoxy]propoxy}benzyl)imino]methyl}phenol (H(2)L1) and 2-[({2-[3-(2-{[(2-hydroxybenzyl)amino]methyl)phenoxy)propoxy]benzyl)amino)methyl]phenol (H(2)L2), and their metal complexes with Cu(II) and Ni(II) metal ions are reported. The ligands and complexes have been characterized by H-1 NMR, FT-IR, UV-Vis absorption spectroscopy, single-crystal X-ray diffraction, CHN elemental analysis and cyclic voltammetry (CV). The redox behavior of the two complexes has been studied by CV. Copper and nickel complexes of Schiff base (H(2)L1) and reduced Schiff base (H(2)L2) showed different behaviors because the structure of the complexes depends of the ligand. The complex [Cu(2)L1(2)]center dot 2CH(3)OH (1) is dinuclear with the two metal centers bridged exclusively by the ligands, consisting of two distorted square planar CuN2O2 chromophors with large intermetallic separation (8.879 angstrom). Complex [Ni(4)L2(2)(CH3COO)(4)]center dot 4CH(3)OH (2) consists of tetranuclear Ni-4 unit of two symmetry related hexacoordinated nickel atoms having distorted octahedral NiN2O4 and NiO6 environments, and contains two types of acetate coordination modes, namely, bridging bidentate (mu(2)-eta(1), eta(1)), and asymmetric chelating bridging (mu(2)-eta(1), eta(1)). (C) 2014 Elsevier Ltd. All rights reserved.