Determination of stability constant and evaluation of related thermodynamic parameters of coordination compounds of transition metals with schiff’s base ligands

In continuation of our previous projects here also we are going to report study of the thermodynamic stability constant of transition metal complex with biologically active Schiff’s base ligands. Here we are going to present results of determination of stability constant of complex compounds using ligands derived from 3- Hydroxy phenyl- 8-methyl coumarin imide (HPMCI) with bivalent transition metals of first transition series. Schiff’s base ligands were synthesized by the condensation of 8-methyl coumarin with 3 - amino phenol.
Nitrate salts of bivalent cobalt, nickel, copper, zinc and manganese were estimated by standard 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 0.1 M KNO3 with the help of digital pH meter . Stability constant of complexes of these metals with the ligands were computed at two temperature i.e. 298 K and 308 K by Irving-Rossotti titration technique1 modified by Calvin-Bjerrum2.
The stability constant values of metals for the given ligand at both the temperatures were found to be Cu (II) > Ni (II) > Co(II) > Zn (II) > Mn(II) stability of complex of given metal and given ligand is higher at 298 K than at 308 K.