DETERMINATION OF STABILITY CONSTANT OF METAL COMPLEXES OF CO(II), NI(II) AND CU(II) WITH SCHIFF BASES OF 3-BROMO-4-AMINO TOLUENE BY POTENTIOMETRIC TITRATION TECHNIQUE

Schiff base namely 1-(2-bromo-4-methyl phenyl)-2-(4-chlorophenyl) azomethine i.e.BMPCA and 1-(2-bromo-4-methyl phenyl)-2-(4-nitrophenyl) azomethine i.e.BMPNA have been synthesized and characterized by Elemental analyses, IR and 1H NMR. Stability constant of BMPCA and BMPNA and its Metal complexes with Cu (II), Co (II) and Ni (II) have been determined by using Calvin ? Bjerrum pH -metric titration technique as adopted by Irving-Rossotti. The potentiometric studies were carried out at constant temperature 27˚?0.5˚C and at ionic strength of 0.1 M KNO3 in 60:40 % (V/V) 1,4-dioxane ? water system . In this work we have calculated proton- ligand stability constant (pK1H) and metal-ligand stability constant (log k1) values by Pointwise calculation method and Half Integral method. The order of the stability constants of the formed complexes observed in BMPCA is Co>Cu>Ni and in BMPNA is Co>Ni>Cu.