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

The 3A-deoxy-3A-(2-methylaminopyridine)-2A(S),3A(R)-beta-cyclodextrin (CDampy3) was synthesized and characterized by NMR spectroscopy. The proton and copper(II) complex formation and stability of this new beta-cyclodextrin derivative were determined by potentiometric and calorimetric investigations, carried out in aqueous solution at 25degreesC and I=0.1 mol dm(-3) (KNO3). The DeltaHdegrees and DeltaSdegrees 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 beta-cyclodextrin. The comparison between the log K values of copper(II) complexes with CDampy3 and those of 6-deoxy-6-(2-methylaminopyridine)-beta-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. (C) 2002 Elsevier Science Ltd. All rights reserved.