Potassium-39 nuclear magnetic resonance study of the complexation of potassium thiocyanate by dibenzo-30-crown-10 in nitromethane

A 2:1 potassium: dibenzo-30-crown-10 complex is formed in nitromethane solution. Taking into account the ion-pairing equilibrium of KSCN in that solvent, an equilibrium constant for the 2:1 complex formation (K2c = 52 ± 5) has been calculated. The characteristic K-39 relaxation rate and chemical shift of the 2:1 complex are compatible with an open structure of the crown, in which the two potassium cations are exposed to the solvent molecules and the thiocyanate counteranion.