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,[CuL 2] were synthesized and characterized by the analytical and spectroscopic methods such as elemental analyses, FT-IR, 1 H, 13 C 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⋯ Ndouble bondN stabilizing the structure. The crystal structure of the Cu (II) was solved in the triclinic space group P 1¯. 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.