Synthesis of L-cystine bridged bis(β-cyclodextrin) and its cooperative binding toward guest molecules

A novel P-cyclodextrin derivative, L-eystine bridged bis(P-cyclodextrin) I has been synthesized and characterized by H-1 NMR, C-13 NMR, C-13, Raman and combustion analyses. Spectrofluorometric titrations have been performed in aqueous phosphate buffer solution (pH=7.20) at 25 degreesC to give the complex stability constants (K-S) and Gibbs free energy changes (-DeltaGdegrees) for the stoichiometric 1 : 1 inclusion complexation of I with four dyes. The binding abilities and molecular selectivities are discussed from the viewpoint of size/shape-fit and electrostatic interactions between hosts and guests. 2D ROESY investigation for the complexation between host and guest further confirms the cooperative binding of bridged cyclodextrin 1 with guest.