2-Hydroxybenzaldehyde-(4,6-Dimethylquinolin-2-yl)-Hydrazone (HBDH), Synthesis, Characterization, and Ligational Behavior Towards Some Metals

Abstract

2-Hydroxybenzaldehyde-(4,6-dimethylquinolin-2-yl)-hydra-zone, and its metal complexes with Cu(II), Co(II), Ni(II), and Zn(II) have been synthesized and characterized using elemental analyses, spectral analyses (IR, UV, ¹ H-NMR, MS), thermal analyses (TGA and DTG), conductance and magnetic measurements. The results showed that 2-hydroxybenzaldehyde-(4,6-dimethylquinolin-2-yl)-hydrazone acts as mononegative tridentate ligand coordinating to the metal ions through quinoline nitrogen, azomethine nitrogen and phenolic oxygen after deprotonation. The difference between ν _as and ν _as stretching vibrations indicates that acetate group binds to the metal ions in a bi-dentate fashion. An octahedral stereochemistry has been suggested for all metal ions. The vibrational spectra of the ligand and its metal complexes have been calculated using semi-empirical calculations, AM1, PM3 and ZINDO/1 methods, to facilitate the assignments of the experimental spectra. Also, the optical band gap (E_g) of the metal complexes has been calculated. The optical transition energy (E_g) is direct and equals 2.40, 2.62 and 2.71 ev for Co, Ni and Cu complexes, respectively.

Keywords:

• 2-hydroxybenzaldehyde-(4,6-dimethylquinolin-2-yl)-hydrazone
• metal complexes
• spectral analyses
• optical band gap