The T2 NMR relaxation times of water protons have been measured to study the stepwise complex formation equilibria in the iron(III)-thiocyanate system in aqueous solution in a wide total iron(III) (0.0025-0.3 M) and total thiocyanate (0-3.0 M) concentration range, in 3 M Na(ClO4, SCN), at 25 °C. The measured relaxation rates are interpreted as a linear combination of the concentration of the different complexes. With this assumption, the following stepwide formation constants are given: log K1 = 2.53, log K2 = 1.35, log K3 = 1.31, log K4 = 1.33, log K5 = -0.32. The ratio of the stepwise equilibrium constants and the molar relaxation coefficients are interpreted by assuming octahedral-tetrahedral configuration equilibria in case of the bis, tris and tetrakis complexes.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry