Protolitic Equilibria and Stability Constants of Mn (II) and Ni (II) Complexes of 3-formylpyridine Thiosemicarbazone in Sodium Dodecyl Sulphate(SDS)-Water Mixture

Abstract

Protonation constant of nicotinaldehyde thiosemicarbazone (NTSC) and its complexation with Mn (II) and Ni (II) were studied in SDS-water (1.15%w/v) mixture at 303K under nitrogen atmosphere and an ionic strength of 0.1 mol dm^-3 pH-potentiometrically. The protonation constant of the ligand and stability constant of its Mn (II) and Ni (II) complexes were calculated by using MINIQUAD 75 computer program, and species distribution diagrams were produced using the HySS computer program. Selection of the best fit chemical models is based on statistical parameters. The predominant species detected for both metals for 1:1 and 1:2 ratios were ML, MLH; ML₂, ML₂H₁ and ML₂H₂ respectively. The appropriateness of experimental conditions is verified by introducing errors deliberately in the concentrations of ingredients of the solution. Distribution diagram and plausible equilibria for the formation and possible structure of the complex species are also presented.