Synthesis, characterization and X-ray crystal structures of copper(II) and nickel(II) complexes with potentially hexadentate Schiff base ligands

Copper(II) and nickel(II) complexes of potentially N2O4 Schiff base ligands 2-({[2-(2-{2-[(1-{2-hydroxy-5-[2-phenyl-1-diazenyl]phenyl}methylidene)amino] phenoxy}ethoxy) phenyl]imino}methyl)4-[2-phenyl-1-diazenyl]phenol (H2L1) and 2-({[2-(4-{2-[(1-{2-hydroxy-5-[2-phenyl-1-diazenyl]phenyl}methylidene)amino] phenoxy}butoxy) phenyl]imino}methyl)4-[2-phenyl-1-diazenyl]phenol (H2L2) prepared of 5-phenylazo salicylaldehyde (1) and two various diamines 2-[2-(2-aminophenoxy)ethoxy]aniline (2) and 2-[4-(2-aminophenoxy)butoxy]aniline (3) were synthesized and characterized by a variety of physico-chemical techniques. The single-crystal X-ray diffractions are reported for CuL1 and NiL2. The CuL1 complex contains copper(II) in a near square-planar environment of N2O2 donors. The NiL2 complex contains nickel(II) in a distorted octahedral geometry coordination of N2O4 donors. In all complexes, H2L1 behaves as a tetradentate and H2L2 acts as a hexadentate ligand. Cyclic voltammetry of copper(II) complexes indicate a quasi-reversible redox wave in the negative potential range.

Graphical abstractCopper(II) and nickel(II) complexes of potentially N2O4 Schiff base ligands were synthesized and characterized by a variety of physio-chemical techniques. In this work, emphasis has been given to the examination of structural relationships in the complexation behavior. We also assume that increasing the length of alkyl linkage may induces a distortion of the coordination geometry from square-planar to octahedral.Figure optionsDownload full-size imageDownload as PowerPoint slide