Synthesis and coordination properties of functionalized β-cyclodextrins. Thermodynamic of proton and copper(II) complexes of 3A-deoxy-3A-(2-methylaminopyridine)-2A(S),3A(R)-β-cyclodextrin in aqueous solution

The 3A-deoxy-3A-(2-methylaminopyridine)-2A(S),3A(R)-β-cyclodextrin (CDampy3) was synthesized and characterized by NMR spectroscopy. The proton and copper(II) complex formation and stability of this new β-cyclodextrin derivative were determined by potentiometric and calorimetric investigations, carried out in aqueous solution at 25 °C and I=0.1 mol dm−3 (KNO3). The ΔH° and ΔS° values allowed to bring to light the role of the hydrogen bond between the amine and the hydroxyl groups in the basicity decrease of NH group of this 3-functionalized β-cyclodextrin. The comparison between the log K values of copper(II) complexes with CDampy3 and those of 6-deoxy-6-(2-methylaminopyridine)-β-cyclodextrin (CDampy6) allowed to determine the donor atoms involved in the coordination to metal ion. The high stability constant of [Cu(CDampy3)]2+ in comparison with [Cu(CDampy6)]2+ was attributed to the involvement of the OH groups in the binding to copper(II) ion. [Copyright &y& Elsevier]