Determination of thermodynamic stability constant of bivalent transition metal complexes with schiffs base as ligands

In continuation of our previous work here also, we have been interested in studying the stability of complexes of transition metals with biologically active ligands.
Here we are presenting determination of stability constant of complex compounds using ligands synthesised from 5-Methyl furan-2-carbaldehyde and 7- methoxy naphthalene- 2 – amine with bivalent transition metals i.e. Co(II), Ni(II), Cu(II) and Zn(II).
Schiff’s base ligands were synthesized by the condensation reaction of 5-Methyl furan-2-carbaldehyde with 7- Methoxy naphthalene – 2 – amine. Nitrate salts of divalent cobalt, nickel, copper and zinc were estimated by standard volumetric and gravimetric methods. Ligand was analysed for elements by reported methods. pH metric titrations were carried out in an inert atmosphere of nitrogen gas at constant ionic strength of 0.1M KNO3 with the help of digital pH meter.Stability constant of complexes of these metals with the ligands synthesized were computed by Irving- Rossoti technique1 modified by Calvin Bjerrum2 at temperatures 298K.
The stability constant values of metals for the given ligand at the given temperature were found to be in the order Cu (II) > Ni(II), Co(II) > Zn (II).
This result is in agreement with the natural order proposed by Irving-William.