Determination of Stability constants Nickel binary and ternary complexes in aquesous DMSO by Pontentiometric method

The stability constants of some of the binary and ternary system involving Nickel(II) have been studied. Bis-(pyridyl) benzilidene acts as a primary ligand. Glycine, L-alanine, L-phenylalanine, L-leucine and L-valine were acts as a secondary ligand. The stability constants of complex are calculated by SCOGS computer program. The reported values are ± 0.02 log unit accuracy. The protonation constants values increase with an increasing percentage of dimethyl sulphoxide. Protanation constants values for the glycine, L-valine ternary complexes higher stability constants indicate that inductive effect is predominant than steric effect. Whereas L-Phenylalanine ternary system has high stability constants than other ternary complexes due to stacking interaction between phenyl ring of phenylalanine and phenyl ring of primary ligand. The order of stability constant of ternary systems is Ni(bpb)(phe)2 > Ni(bpb)(leu)2 > Ni(bpb)(val)2 > Ni(bpb)(gly)2. (paper)