An azo-azomethine ligand and its copper(II) complex: Synthesis, X-ray crystal structure, spectral, thermal, electrochemical and photoluminescence properties

Abstract

In this study, a new azo-azomethine ligand, 4-[(E)-phenyldiazenyl]-2-[(E)-{[4-(propan-2-yl)phenyl]imino}methyl]phenol (HL) and its Cu(II) complex, [CuL2] were synthesized and characterized by the analytical and spectroscopic methods such as elemental analyses, FT-IR, 1H, 13C NMR and mass spectra. Molecular structures of the ligand and its Cu(II) complex were determined by single crystal X-ray diffraction studies. In the structure of the ligand, there is an intramolecular phenol-imine hydrogen bond (O1⋯N1) with a distance of 2.580(3)Å. There are also intermolecular hydrogen bond type interactions CH⋯O and CH⋯NN stabilizing the structure. The crystal structure of the Cu(II) was solved in the triclinic space group P1¯. In the structure of the complex, the Cu(II) ion is four coordinate bonded to two phenolate oxygens and two imine nitrogens of two ligand molecules in an approximate square-planar geometry. The Cu–O bonds are in trans configuration. Thermogravimetric data revealed that the Cu(II) complex is thermally more stable than the azo-azomethine compound (HL). Upon coordination with Cu(II) ion, both excitation and emission intensities of the ligand shifted to lower values.