A MOLECULAR CLIP THAT BINDS AROMATIC GUESTS BY AN INDUCED-FIT MECHANISM

The conformational behavior and binding properties of a novel molecular receptor consisting of a diphenylglycoluril unit flanked by two 2,7-disubstituted naphthalene rings is described. The molecule appears in three conformations. These conformations differ in the way that the naphthalene rings are oriented with respect to the two phenyl groups on the concave side of the glycoluril moiety, viz. anti-anti, syn-anti, and syn-syn. The receptor is able to change from one conformation to another by flipping the naphthalene walls. The mechanism and the rate constants for this process were determined by 2D EXSY NMR techniques. One of the three conformations contains a cavity, within which aromatic guest molecules of appropriate size can be bound selectively.