Cu(II) Ion Complexation by Excess of  -cyclodextrin in Aqueous Alkaline Solutions

Polarographic investigations of Cu(II) complexation in aqueous alkaline solutions containing an excess of β-cyclodextrin (β-CD) show that the complex formation begins at pH > 11, the concentration of free (uncomplexed) Cu(II) ions being in the range from ca. 10-12 to ca. 10-19 M, depending on β-CD concentration and pH. The formation of copper(II) 1:1 hydroxy-complex with β-cyclodextrin anion (CD2-) was observed at pH 11–14. The logarithm of the stability constant of CuCD(OH)2- 2 complex is 19.7 ± 0.2 (20 °C, ionic strength 1.0), the values of the molar extinction coefficient and of the diffusion coefficient of this complex are 50 M-1 cm-1 (λmax = 660 nm) and 1.0 × 10-6 cm2 s-1, respectively.