Notes. Studies on the solubility of 2,2′-bipyridyl,1,10-phenanthroline, and their tris iron(II) perchlorates in methanol–water mixtures, and the determination of the ‘medium effect’ of ions

Abstract

The solubilities of 2,2′-bipyridyl (bipy),1,10-phenanthroline (phen), and their complexes [FeL₃]²⁺ as perchlorates have been determined in water and methanol–water mixtures (up to 87 wt. % organic solvent) at 295 K. The changes in free energies of transfer, Get, thus obtained have been coupled with the free energies of transfer for the reactions (i) and (ii) to determine the ΔG^⊖_t values of the ions Hbipy⁺(or Hphen⁺)⇌ bipy (or phen)+ H⁺(i), [Fe(bipy)₃]²⁺{ or [Fe(phen)₃]²⁺}⇌ Fe²⁺+ 3 bipy (or phen)(ii) H⁺, Hbipy⁺, Hphen⁺, and Fe²⁺. The ΔG^⊖_t(H⁺) values in methanol–water reported are qualitatively in good agreement with literature values, although quantitative disagreement exists. Values of ΔG^⊖_t(Fe²⁺) from water to methanol–water mixtures have also been calculated.