Simultaneous determination of thermodynamic and kinetic parameters of aminopolycarbonate complexes of cobalt(II) and nickel(II) based on isothermal titration calorimetry data.

Abstract

The influence of the different side chain residues on the thermodynamic and kinetic parameters for complexation reactions of the Co2+ and Ni2+ ions has been investigated by using the isothermal titration calorimetry (ITC) technique supported by potentiometric titration data. The study was concerned with the 2 common tripodal aminocarboxylate ligands, namely, nitrilotriacetic acid and N-(2-hydroxyethyl) iminodiacetic acid. Calorimetric measurements (ITC) were run in the 2-(N-morpholino)ethanesulfonic acid hydrate (2-(N-morpholino) ethanesulfonic acid), piperazine-N,N'-bis(2-ethanesulfonic acid), and dimethylarsenic acid buffers (0.1molL-1 , pH 6) at 298.15K. The quantification of the metal-buffer interactions and their incorporation into the ITC data analysis enabled to obtain the pH-independent and buffer-independent thermodynamic parameters (K, ΔG, ΔH, and ΔS) for the reactions under study. Furthermore, the kinITC method was applied to obtain kinetic information on complexation reactions from the ITC data. Correlations, based on kinetic and thermodynamic data, between the kinetics of formation of Co2+ and Ni2+ complexes and their thermodynamic stabilities are discussed.