Stability of a Dinuclear Cu(II)–β-Cyclodextrin Complex

Abstract

Cu(II) ions form a dinuclear complex with the tetraanion of β-cyclodextrin (CD4-) in alkaline solutions under conditions of metal ion excess. The spectrophotometric method of ligand displacement was used for the determination of the stability constant of this complex using EDTA and OH- ions as competitive ligands. The results obtained are in agreement with the 2:1 stoichiometry of the complex, namely Cu2CD, the logarithm of the stability constant being 39.2±0.2. This complex predominates in the pH range from 12.5 to 14.3 (3 M NaOH solution), transforming with the increase in alkalinity to