SYNTHESIS AND ELECTROCHEMICAL STUDIES OF CU(II) AND NI(II) COMPLEXES WITH TETRADENTATE SCHIFF-BASE LIGANDS

A series of tetradentate Schiff-base ligands; 1,3-bis(salicylideneimin o) propane, 1,4-bis(salicyli-deneimino)butane, and 1,5-bis(salicyliden eimino)pentane, and their Cu(II) and Ni(II) complexes have been synthe sized. The properties of ligands and complexes have been characterized by elemental analysis, IR, NMR, UV-Vis spectra molar conductance, and thermogravimetric anaylsis. The mole ratio of Schiff base to metal at complexes was found to be 1:1. All complexes were four-coordinated co nfiguration and non-ionic compound. The electrochemical redox processe s of the ligands and their complexes in DMF solution containing 0.1 M TEAP as supporting electrolyte have been investigated by cyclic voltam metry, chronoamperometry, differential pulse voltammetry at glassy car bon electrode, and by controlled potential coulometry at platinum gauz e electrode. The redox process of the ligands was highly irreversible, whereas redox process of Cu(II) and Ni(TI) complexes was observed as one electron transfer process of quasi-reversible and diffusion-contro lled reaction. Also the electrochemical redox potentials of complexes were affected by chelate ring size of ligands. The diffusion coefficie nts of Cu(II) and Ni(II) complexes in DMF solution were determined to be 4.2-6.6 x 10(-6) cm(2)/sec. Also the exchange rate constants were d etermined to be 3.6-9.7 x 10(-2) cm/sec.