Tetradentate schiff base ligands of 3,4- diaminobenzophenone: Synthesis, characterization and thermodynamics of complex formation with Ni(II), Cu(II) and Zn(II) metal ions

Abstract

Some new symmetrical diimino tetradentate Schiff base ligands were synthesized by the reaction of 3,4-diaminobenzophenone with salicylaldehyde derivatives, such as [N,N?-bis(4-methoxysalicylaldehyde)- 3,4-diaminobenzophenone] (L1), [N,N?-bis(5-methoxysalicylaldehyde)- 3,4-diaminobenzophenone] (L2), [N,N?-bis(5-bromosalicylaldehyde)-3,4- diaminobenzophenone] (L3), [N,N?-bis(5-nitrosalicylaldehyde)-3,4- diaminobenzophenone] (L4). Additionally, a tetradentate Schiff base ligand [N,N?-bis(3-methoxysalicylaldehyde)-3,4-diaminobenzophenone] (L5), was synthesized. All the Schiff bases and their Ni(II), Cu(II) and Zn(II) complexes were characterized using elemental analysis and infrared, electronic, mass and 1H-NMR spectroscopy. The formation constants of the complexes were measured using UV-Vis spectroscopic titration at constant ionic strength 0.1 M (NaClO4), at 25?C in dimethylformamide (DMF) as solvent.