COMPLEX FORMATION AND THERMODYNAMICS IN [CD-L-AMINO ACID-VITAMIN-PPI COMPLEXES AT DROPPING MERCURY ELECTRODE

摘要

This paper describes the ternary complexes formation of Cd(II) with L-glutamine, L-asparagine, L-valine, L-leucine, a-alanine and L-glycine as primary ligands and vitamin-PP (nicotinamide) as secondary ligand by polarographic technique at pH = 7.30 ± 0.01, μ = 1.0 MKNO3 at 25 and 35℃.Cd(II) formed 1:1:1, 1:1:2, and 1:2:1 complexes with these ligands, as confirmed by the Schaap and McMaster method. The sequence of the stability constant of complexes was L-glutamine < L-asparagine < L-valine < L-leucine < a-alanine < L-glycine. The cathodic reduction of the complexes involves 2 electrons and the waves were reversible and diffusion-controlled in nature. The changes in thermodynamic parameters such as enthalpy AH, free energy AG and entropy AS were also determined that showed that the complexes are lesser stable at higher temperature.