Palarographic studies of Pd (II), Pt (II) and Co (III) complexes of Polyaza Ligands

Abstract

The polarographic technique gives a convenient method for studying redox reactions. The complexes studied give well defined, diffusion controlled one electron transfer reduction waves. The waves are irreversible in behavior. In case of P+(II) complexes, a regular cathodic shift in half wave potential of changing over from the trans structural macro cycle to the is observed. The redox properties of polyaza macrocyclic ligands have been of continued interest. As a result of these studies several macro cyclic complexes have been used as oxidant, reductants and electro catalysts. Earlier work on the redox behavior of macrocyclic complexes had mainly dealt with unsaturated systems. Later studies have dealt with many types of saturated systems also. It is important to study the effect of ligand structure, chelate ring size, donar unsaturation, substituent pattern and relative position of five and six membered chelate rings. It has been shown that a decrease in the ligand field strength of the macrocyclic ligands conclude in an anodic shift in the oxidant and reduction potentials. A change in the nature of the ring substituents changes the redox potential. The changes in the redox potential in these complexes are influence the substituents on the metal nitrogen interaction. In this we discuss the polarographic behavior of the complexes of (L1) Me2 (ET4) (14) diene (C20H40N4), Me2 (ET4) (14) ane (C20H44N4), (L3) Me6 (ET4) (14) diene (C16H35N4) and, (L4) Me2 (14) ane (C16H36N4). The polarograms of the complexes in aqueous solution were marked on a Metrohm Polarecord 50 usig a dropping mercury electrode (d.m.e.) as the working device. To choose a correct supporting electrolyte, polarographic wave of a few complexes were recorded in different electrolytes. It was observed that the best waves were prepared in 0.1 M sodium perchlorate. The one electron transfer irreversible waves related to the reduction of Pt (II) to Pt (I) and Pd (II) to Pd (I). It is reasonable to assume that the Pt – N distance is the significant factor. It has been seen that a change in the symmetry of the ligand result in change in the ligand field strength.

Keywords

• Polarographic technique
• unsaturated systems
• Redox potential