BINDING FEATURES OF MOLECULAR CLIPS DERIVED FROM DIPHENYLGLYCOLURIL

The structure and binding properties of a series of receptor molecules based on the building block diphenylglycoluril are described. These r eceptors bind dihydroxy-substituted aromatic guests in chloroform solu tion by means of hydrogen bonding and pi-pi stacking interactions. IR difference spectroscopy shows that the hydrogen bonds are formed betwe en the OH groups of the guest molecule and the pi-electrons of the ure a carbonyl groups present in the receptor. The structure of the comple xes was further investigated by comparing the complexation-induced shi fts in the H-1 NMR spectra with the calculated shifts for a number of geometries of the host-guest complexes. These data demonstrate that th e guest molecules are clamped within the cavity of the receptor.