Complexation of nickel (II) ion with B3 vitamin in aqueous dimethyl sulfoxide

The stability change of nickel(II) ion complexes including one and two nicotinamide (B3 vitamin) molecules in aqueous dimethyl sulfoxide (XDMSO = 0–0.85 m.f.) was studied at 298.2±0.1 K and 0.25 ionic strength value (NaClO4) using the potentiometric method. The first stage constant of complexation increased until organic solvent concentration was 0.5 m.f. and reduced at higher DMSO content. The difference between complex and central ions solvation is a dominating contribution into the Gibbs energy change of mononicotinamide complex formation reaction. When the second ligand molecule was bonded into the coordination compound, the nicotinamide contribution to ΔtrGr rose and became prevailing at XDMSO = 0.7–0.85. The ligand was found to replace a water molecule in the coordination sphere of the cation according to spectrophotometric study results.