Determination of stepwise stabilty constants and Gibb’s free energy change of trisprolinato complexes of some divalent transition metal ions

Abstract

The overall stability constants of manganese (II), iron (II), cobalt (II), nickel (II), copper (II), and zinc (II) complexes with proline were  determined by potentiometric titration of sodium prolinate with the  corresponding salt of the divalent metal in aqueous media. The values of the constants (Logâ) were found to be 19.45, 19.23, 19.41, 19.23, 9.76 and 18.51 for manganese (II), iron (II), cobalt (II), nickel (II), Cu (II) and Zn (II) complexes respectively using ORIGIN 50 computational method. The Gibbs free energies of the complexes were found to be in the range of -105.62 to – 112.75 for manganese (II), iron (II), cobalt (II), nickel (II), copper (II) and zinc (II) complexes respectively. The values indicate good stability for all the prolinato metal complexes.

Keywords: Proline, stability constant, Gibb’s free energy, divalent metals and enzymes