MOLECULAR RECOGNITION STUDY ON SUPRAMOLEC ULAR SYSTEM .12. MOLECULAR RECOGNITION OF 4-SUBSTITUTED PHENOLS BY CYCLODEXTRINS AND BINUCLEAR CU(II) COMPLEXES WITH CYCLODEXTRINS

The spectrophotometric titrations have been performed in aqueous solut ions 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 copp er (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 complexatio n 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 o f the size/shape-fit, multiple recognition, induced-fit relationship b etween the host cavity and the guest molecules, The results obtained i ndicate that the binuclear Cut (II) complex with beta-cyclodextrin pos sesses the special binding ability and molecular selectivity for 4-sub stituted phenols.