Molecular recognition study on supramolecular system(XII) - Molecular recognition of 4-substituted phenols by cyclodextrins and binuclear Cu( II) complexes with cyclodextrins

The spectrophotometric titrations have been performed in aqueous solutions with different pH values at 25.0 degrees C to give the stability constants (IgK(s)) for inclusion complexation of various 4-substituted phenols with alpha-, beta- and gamma-cyclodextrins and binuclear copper (II)-alpha, beta-cyclodextrins complexes, The stoichiometry of the supramolecular complexes formed is 1:1 for all the host cyclodextrins and binuclear copper(II)-cyclodextrins complexes inclusion complexation with various guest 4-substituted phenols, The molecular recognition mechanism for 4-substituted phenols of the cyclodextrins and binuclear Cu(Il) complexes with cyclodextrins is discussed from the viewpoint of the size/shape-fit, multiple recognition, induced-fit relationship between the host cavity and the guest molecules, The results obtained indicate that the binuclear Cut (II) complex with beta-cyclodextrin possesses the special binding ability and molecular selectivity for 4-substituted phenols.