Synthesis of new asymmetrical diimin compounds, preparation of their metal complexes and investigation of tautomeric properties

In the present study, two Schiff bases were synthesized from the condensation of 4-nitrobenzaldehyde with 2-aminophenol and 3-amino-2-naphtol. The nitro group of the Schiff bases were reduced to amino group with sodium dithionite (Na2S2O4). The amino compounds obtained were reacted with salicylaldehyde and 2-hydroxy-1-naphthaldehyde, three new asymmetric diimine compounds were synthesized and their Ni(II) and Fe(III) complexes were obtained.The structures of the ligands and the complexes were characterized by elemental analyses, spectroscopic methods and mass spectrums, TGA, magnetic susceptibility and conductivity measurements. All the complexes were found to have dimeric structure. Square planar geometry for the two Ni(II) complexes and octahedral geometry for the other Ni(II) and Fe(III) complexes were suggested.The UV-visible spectrum of the ligands were taken in DMSO, methanol, chloroform, toluene, cyclohexane, acidic and basic solutions. The phenol-imine keto-amine tautomeric equilibrium of the ligands were investigated by IR, 1H-NMR, 13C-NMR and UV-visible spectroscopy.