Molecular recognition properties of novel molecular tweezers 1～6 have been investigated by using aniline, p-nitroaniline and p-methoxyaniline. The association constants (K_a) and Gibbs free energy changes (ΔG⁰) have been measured by UV-Vis spectroscopic titration for inclusion complexes of these molecular tweezers with aromatic amines in CHCl₃ at 25 ℃. The results show that all the molecular tweezers have good recognition properties for the guests examined and the supramolecular complexes formed between the hosts and guests consist of 1∶1 host and guest molecules. The main driving forces are the multiple hydrogen bonding and π-π stacking interaction between host and guest molecules. The molecular recognition ability is discussed in terms of the size/shape-fit and geometrical complementary relationship as well as the recognition model between host and guest molecules. ¹H NMR spectroscopy and computer-aided study have been employed to elucidate the experimental results.

Key words: molecular recognition, UV-Vis spectral titration, molecular tweezer, deoxycholic acid