Synthesis and characterization of thermally stable Schiff base polymers and their copper(II), cobalt(II) and nickel(II) complexes

In this study, the Schiff base monomers [(M1; N,N′-p-phenylenebis(salicylideneimine)) and ethylenediamine (M2; N,N′-p-ethylenebis(salicylideneimine))] were synthesized by the condensation reaction between p-phenylenediamine and aromatic aldehydes. The Schiff base polymers (SBPs) having double azomethine groups were prepared by oxidative polycondensation (OP) reaction of monomers in aqueous alkaline medium with NaOCl [P1; poly-(N,N′-p-phenylenebis(salicylideneimine)) and P2; poly-(N,N′-p-ethylenebis(salicylideneimine))] as the oxidant at 90 °C. Average molecular weights of SBP were determined by gel permeation chromatography (GPC). Metal complexes of the SBP were synthesized by the reaction of polymers and metal salts. The monomers and SBP were characterized by elemental analyses, GPC, thermogravimetric analyses, UV-Vis, FT-IR, 1H and 13C NMR spectroscopic studies. Also the new Cu(II), Ni(II) and Co(II) complexes of SBP were prepared and characterized by elemental analyses, UV-Vis, FT-IR, atomic absorption spectroscopy (AAS), thermogravimetric analyses and magnetic susceptibility measurements. The results suggested that the SBP and metal ions in 1:1 molar ratio produced binuclear complexes with oxygen and nitrogen donor atoms. All synthesized complexes have dimeric structures by the polymeric ligand units. The weight losses of P1-Cu, P2-Ni and P1-Co complexes were found as 57%, 60% and 61%, at 900 °C, respectively. Thermal stability of P1 complexes is higher than that of P2 complexes. Magnetic moment studies showed that all complexes have various configurations. The metal ion uptake studies were done by batch technique. The polymer P1 was determined to be more effective in removing Cu(II) ions than the P2 polymer in batch technique.