Document Type: Research Paper
Department of Chemistry, Islamic Azad University, Firouzabad Branch, Firouzabad, Iran
Chemistry Department, College of Sciences, Shiraz University, Shiraz 71454, I. R. Iran
Some new symmetrical tetraaza Schiff base ligands containing 2-quinolinecarboxaldehyde moiety formed from condensation reaction of 2-quinolinecarboxaldehyde and o-phenylenediamine derivatives, such as N, Nˊ-bis(2-quinolylmethylidene)-4-methoxy-1, 2-phenylenediimine (L1), N, Nˊ-bis(2-quinolylmethylidene)-4-methy-1, 2-phenylenediimine (L2), N, Nˊ-bis(2-quinolylmethylidene)-4-chloro-1, 2-phenylenediimine (L3), N, Nˊ-bis(2-quinolylmethylidene)-4-carboxylic-1, 2-phenylenediimine (L4), N, Nˊ-bis(2-quinolylmethylidene)-4-nitro-1, 2-phenylenediimine (L5), and their Ni(II), Cu(II), Zn(II) complexes, have been synthesized. The ligands and their metal complexes have been characterized by molar conductance, elemental analysis, IR, 1H-NMR and UV-Vis spectroscopy. The formation constant and the free energy of the complexes were determined using electronic spectroscopic titration at constant ionic strength 0.1 M (NaClO4), at 25°C in MeOH solvent. The comparison of the formation constants and the thermodynamic parameters show that the trend of complex formation toward a given ligand is as follows: L2 > L1 > L3 > L5 > L4 . The trend for complex formation of the metal ions with a given ligand is as follows: Zn (II) > Cu (II) > Ni (II).