Synthesis of new Schiff bases and their metal complexes from amines prepared with reduction of aromatic nitro compounds, investigation of potentiometric properties

In the present study, six nitro Schiff bases were synthesized from the reaction of 5-(2-nitrophenyl) furfural and 5-nitrothiophene-2-aldehyde with o-aminophenol, 2-amino-5-klorophenol and 2-amino-p-cresol. The nitro groups these Schiff bases were reduced with Na2S2O4. After the amino compounds obtained were reacted with 2-hydroxy-1-napthaldeyde, six new asymmetric diimine compounds and their Ni(II) complexes were synthesized. The structures of the ligands and the complexes were characterized by elemental analysis, spectroscopic methods, TGA, magnetic susceptibility and conductivity measurements. All of complexes, except two, were found to have dimeric structure. Square planer geometry for all the complexes were suggested.Protonation constants of the Schiff bases and diimine ligands and stability constants of the complexes have been determined potentiometrically in 1:1 ethanol-water medium at 25 ± 0,1 0C. Effects of substituents on the protonation and stability constants were discussed.