Free energies, enthalpies and entropies of the monothiocyanate complex formation of trivalent metals in dimethyl sulphoxide solutions

Abstract

Formation of the InSCN(DMSO)²⁺₅ complex in DMSO solution has been studied spectrophotometrically and calorimetrically and the complete thermodynamic characteristics, ΔG°, ΔH° and ΔS°, of the complex-forming reaction have been derived. These results and analogous thermodynamic parameters obtained previously for AlSCN(DMSO)²⁺₅, GaSCN(DMSO)²⁺₅ and FeSCN(DMSO)²⁺₅ complex formation are discussed in terms of factors controlling the stability of the complexes. It has been found that the entropy effect is responsible for the stability of the monothiocyanate complexes of A1^III, Ga^III, In^III and Fe^III in DMSO solutions.