Six molecular tweezers (1～6) have been synthesized based on the incorporation of multiple hydrogen-bonding groups into the cleft to provide both orientation and selective complexation of substrate. Molecular recognition properties of these receptors for barbiturate, urea, diphenylmethanone and glutarimide have been investigated by UV- visible spectroscopic titration, which indicates that the supramolecular complexes consist of 1:1 host and guest molecules. The main driving forces are the multiple hydrogen bonding in molecular recognition. The molecular recognition ability is discussed from the viewpoint of the size/shape-fit and geometrical complementary relationship. Computer-aided study and ~1H NMR spectroscopy have been employed to elucidate the binding behavior of these molecular tweenzers.

Key words: hydrogen bonding, molecular recognition, UV, BARBITAL, UREA, DIPHENYLMETHANONE, DIPHENYLMETHANONE, FREE ENERGY