Synthesis, crystal structure, experimental and theoretical studies of tetradentate N2O2 Schiff base ligand and its Ni(II) and Pd(II) complexes

The synthesis of a novel ligand bis(3-methoxysalicylidene)-4-methylbenzene-1,2-diamine (H2L) has been carried out by the condensation of 4-methylbenzene-1,2-diamine with 3-methoxysalicylaldehyde. The Ni(II) and Pd(II) Schiff base complexes have been synthesized from the reaction of Ni(OAc)2·4H2O and Pd(OAc)2 with the Schiff base ligand (H2L) in methanol and acetonitrile, respectively. The ligand and its complexes have been characterized by elemental analyses, FT-IR, 1H-NMR and UV–Vis spectroscopy. Moreover, the crystal structure of the ligand has been determined by single crystal X-ray crystallography. To have better understanding of electronic transitions of the ligand and its complexes, density functional theory (DFT) calculations have been performed. The geometries and electronic properties of the compounds have been obtained with the M062X level at Def2-TZVP basis set. Additionally, NBO analysis has been performed to interpret electronic transitions by determining their included occupied and virtual orbitals. The theoretical parameters confirmed the suggested structure of complexes. The spectroscopic data obtained from DFT calculations show acceptable agreement with the experimental results.