Grisorixin, an ionophorous antibiotic of the nigericin group. Part IV. Complexation of monovalent cations

Abstract

Data on interactions between monovalent alkali metal, thallium, and silver cations and a new antibiotic grisorixin in methanol are reported. These were obtained by conductimetric and potentiometric measurements. Two types of interactions were studied, on one hand association of the salts formed between cations and grisorixin carboxylate ion, on the other complexation of the cations by the neutral antibiotic molecule. The magnitude of the equilibrium constants for the first process was ca. 200 times greater than for the second in the case of potassium. For association of salts the following order of selectivity was found: Ag⁺ > Ti⁺ > K⁺ > Rb⁺ > Na⁺ > Cs⁺ > Li⁺, the association constants varying from 10² to 10⁷. The same order of selectivity was found using a liquid phase galvanic cell.